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1. INTRODUCTION

1.1. Background and Justification

Developing countries have many economical and social problems caused by population

increase and lower income per capita. Rapidly increasing populations require more food,

but since most land is already under cultivation, the only way to increase production is to

increase yield and grow more than one crop in a year. Despite the great progress of

mechanization in agriculture, manual workers will still continue to provide the main

source of power for the farmers on small farms of many developing countries (Hopfen,

1969; Allen, 1979; Dibbits, 1991; Awadhwal et al., 1992). In circumstances where

human labour is supplemented by other energy sources to lighten the task or to increase

work capacity, the human energy expenditure might still be considerable. Firstly, an

important source of power to be considered is human power as many areas have no

access to sources of energy except human power; small tractors on small individual farms

are not feasible.

Man powered and other power sourced seeders boost the yield of small holders by placing

seeds in an environment for reliable germination. The main objective of sowing is to put

seeds at a desired depth and spacing within the row. Uniform seed distribution within the

soil results in better germination and emergence and increases yield by minimizing

competition between plants for available light, water, and nutrients. A number of factors

affect seed distribution in soil. Seed metering system, seed delivery tube, furrow opener

design, physical attributes of seed and soil conditions all play a part in determining seed

distribution ( Karayel and Ormerzi 2007).

Manual broadcast sowing often results in uneven seed placement in the soil, which results

in uneven emergence and stands. Seeds may be placed as deep as 2 to 5 cm, where many

seeds will germinate but will not emerge through the soil surface. Other seeds may be

placed very shallow or on the soil surface. These seeds often do not survive due to dry soil

or winter damage. The uneven stands from broadcasting often result in lower yields

comparing with drilling (Herbek and Murdock, 2003).

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According to Herbek and Murdock (2003), the best results in wheat and other crop stand

establishment and yield are obtained by seeding with a grain drill. A drill ensures good

seed-to-soil contact, promotes rapid germination, results in more uniform and optimum

stands, reduces winter injury, and increases yields over broadcast seeding.

Drill planters randomly drop seeds in furrows to form definite rows of established plants.

This type of planter uses a mass flow type seed meter and is extensively used for the

establishment of both winter and summer crops where there is no need to place plants

equidistant down the rows. For example, almost all cereal crops (oats, wheat, barley, etc)

are planted by drill type planters. Reasonably accurate control over the planting rate per

hectare can be attained. Drill type planters are often known as solid crop planters because

of the narrow row spacing typically used. (Murray et al., 2006).

Row crop drills comprise one or several hoppers which contain the seeds of metering parts,

and of equipment for seed placement in the soil. The seed metering device either aims at

equidistant spacing of the seeds or is restricted to feeding a stream of seeds into a

conveying tube. The former case can be defined as precision seeding, whereas for the latter

case, the term bulk seeding might be appropriate. Precision drilling is used mainly for

rather widely spaced crops such as corn, beans, sugar beets and sunflower. With closely

spaced crop like wheat precision drilling is too expensive and therefore bulk drilling is

common (Heege and Billot, 1999).

Inter-row spacing depends on the effective spacing between furrow openers and the

horizontal spread of seed within the furrow. Furrow shape and the design of the seed

placement components are the major variables. To enable the planter to sow a range of

crops it is desirable that row spacing can be adjusted. On wide drill planting machines this

is usually accomplished by altering row spacing as a multiple of the overall opener

spacing, e.g. blanking off the seed flow to every second opener across the width of the

machine effectively doubles the row spacing. On precision type planters, the spacing of the

individual openers can usually be adjusted by sliding and repositioning the furrow openers

on the toolbar/frame. Hence, the pattern resulting from the accurate placement (and

subsequent covering) of groups (or hills) of seed in furrows at about equal intervals to give

definite rows of almost equally spaced groups of plants is achieved by hill seeders (Murray

et al., 2006).

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Moreover, dropping seeds at an equal interval and nearly uniform number has the potential

to further reduce the seed requirement per hectare. This will allow uniform spaced planting

similar to the transplanted crop providing space for growth (Aldas and Sakurai, 2001)

According to Hartley (1999), Placement of fertilizers in relation to seed is critical.

Fertilizers may stimulate or restrict seed germination. Different types of machinery for

fertilizer application include trucks, aircraft and land-powered units. Use of fertilizer

spreaders requires calculation of application rate and calibration of machinery. Fertilizers

are usually ―dry‖ (powders, granules), but may also be supplied as liquids, dissolved

materials, or even gases. In some areas, fertilizer is added into irrigation water. Dry

fertilizers are appropriate for almost every type of crop. Therefore, this work intends to

modify the manually operated rice hill seeder for wheat row seeder with fertilizer

applicator and solve problems associated with manual broadcasting method.

1.2. Statement of the Problem

Manual broadcasting is the oldest method of sowing seeds and fertilizers. This method is

widely practiced by our country‘s farmers for most types of crops. However; this method

of sowing crops has been giving poor yield of harvest per hectare due to several reasons:

Inconvenience for weeding and pest control

Difficult for cultivation

Irregular placement of seeds (overlaps and skips) and

Poor control over depth of seed placement

Moreover, according to Aldas and Sakurai (2001) and Belay and Brink (2006) it requires

more amounts of seed per hectare than row sowing method. Therefore, these problems

need attention and should be solved with replacing the manual broadcasting sowing

method with proper row seeding machine. Accordingly, modification of manually drawn

rice hill seeder developed at Holly Name University, Tagbilaran city, Bohol, Philippines

for wheat bulk seeder, making it fit to the properties of wheat seed and application rate,

considering efficiency and effectiveness is going to be done.

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1.3. Objective of the Study

1.3.1. General Objective

The main objective of this research work is to modify the manually drawn rice hill seeder

(row seeder) developed at Holly Name University, Philippines for wheat with additional

fertilizer application capability.

1.3.2. Specific Objectives

To modify the seed metering device, seed hopper and furrow opener of the machine

for wheat.

To add a fertilizer application metering unit

To determine the draft force required by the machine at actual field condition

To evaluate the performance of the modified seeder in laboratory and actual field.

1.4.Significance of the Study

The main significance of the study is the development of a three row wheat hill seeder with

fertilizer applicator. The surrounding small holder farmers will be the main beneficiary and

the technology can also be disseminated to all over the country and other farmers can

utilize it. Moreover the seeder will be used as teaching aid for practical demonstration in

the department of Agricultural Engineering.

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2. LITERATURE REVIEW

2.1. Overview of Wheat Production in Ethiopia

Ethiopia is the second largest producer of wheat in sub-Saharan Africa, following South

Africa. About 900,000 ha of bread (Triticum aestivum) and durum (T. turgidum var.

durum) wheats are grown in Ethiopia, primarily as highland rainfed crops. Mean wheat

yields are around 1.4 t/ha, well below experimental yields of over 5 t/ha Ethiopia‘s current

annual wheat production of approximately 1.3 million tons is insufficient to meet domestic

needs, forcing the country to import 30 to 50% of the annual wheat grain required. The

yield gap of over 3 t/ha suggests the potential for increasing production through improved

crop management, particularly increased use of fertilizers. However, there is also

justification for examining whether wheat production can be introduced to non-traditional

areas, (Hailu 1991).

Bread wheat accounts for roughly 60% of total wheat production and nearly all cultivars

are derived from modern, semi-dwarf wheats. Durum wheat accounts for most of the

remaining 40%, although emmer wheat (T. dicoccum L.) is also grown. Bread wheat is

produced at slightly higher elevations and on better drained soils than durum wheat, which

is primarily found on poorly drained Vertisols (Hailu 1991). Wheat production constraints

include low soil fertility, grass weed infestations, water logging in Vertisol areas, and

water deficits in short season areas (Tanner et al. 1991). Stripe rust (Puccinia striiformis) is

common at higher elevations (> 2,400 m); stem rust (P. graminis f. sp. tritici) is more

problematic at midelevations (2,000-2,400 m) (Bekele and Tanner 1995).

Double-cropping has recently been demonstrated as a promising option for south eastern

Ethiopia. In the Bale zone of Oromiya Region, the belg rains are sufficiently long and

reliable for wheat or other crops. Double cropping could reduce the negative effects of the

current practice of alternate season fallows: a continuous crop cover would reduce erosion;

alternating crops would help control weeds; and human and animal power could be used

more efficiently, (Tanner et al. 1994)

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2.2.Potential Wheat Production Areas of Ethiopia

Because water deficits and warm night temperatures seemed to be key factors delimiting

bread wheat production areas in Ethiopia, potential new areas for bread wheat production

were identified by assuming that technologies could be developed to allow wheat to be

grown in drier or warmer environments. For drier conditions, such technologies might

include more drought tolerant cultivars, supplemental irrigation from small catchments, or

agronomic practices—such as reduced tillage and residue retention—that reduce runoff.

Growing wheat under warmer conditions might require cultivars with greater heat

tolerance as well as resistance to pathogens that prevail under warmer conditions

(e.g., Helminthosporium sativum) Belay et al., (1999).

Applying the assumption that wheat will grow in areas receiving as little as 300 mm during

the wettest quarter resulted in a surprisingly small addition (4%) to the potential wheat

production area. In contrast, a shift in adaptation to include areas with 2°C warmer

minimum temperatures (e.g., up to 13°C) substantially increase potential wheat area. The

actual impact on total wheat area is impossible to estimate: zones that meet climate criteria

may have unsuitable soils or topography or already be used for other, more profitable

agricultural pursuits. However, as a rough indicator, increasing the minimum temperature

limit by 2°C expanded the potential area suitable for wheat production by 108% (Belay et

al., 1999).

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Figure 2.1: Approximate distribution of traditional wheat production areas of Ethiopia

(from Belay et al., 1999).

2.3.Physical Properties of Seeds and their Use in Designing Bulk Seeders

The knowledge of some important physical properties such as shape, size, volume, surface

area, thousand grain mass, density, porosity, angle of repose, of different grains is

necessary for the design of various separating, handling, storing, drying and planting

systems (Sahay and Singh, 1994). Bulk density, true density, and porosity (the ratio of

intergranular space to the total space occupied by the grain) can be useful in sizing grain

hoppers and storage facilities; they can affect the rate of heat and mass transfer of moisture

during aeration and drying processes ( Kheiralipour et al., 2008).

Seed flow through a planter is dependent on size, shape, sphericity, true density and angle

of repose of seeds. In addition, the impact of seeds on the internal components of the

planter is influenced by the coefficient of restitution of seeds on various impinging

surfaces (Jayan and Kumar, 2004). The static coefficient of friction and angle of repose is

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necessary to design conveying machine and hopers used in planter machines (Karimi et.al,

2009).

The moisture content of seeds according to (RNAM, 1995) is calculated using the

following equation:

𝑀𝑐 =𝑀𝑤−𝑊𝑑

𝑊𝑑 ----------------------------------------------------------------------------------------1

Where, 𝑀𝑐 is moisture content (%) dry basis, 𝑀𝑤 mass of selected seed as bought from

market and 𝑊𝑑 is mass of dried seeds.

According to Mohsenin (1986), the three linear dimensions (namely, length L, width W,

and thickness T) can be measured using digital micrometer and the average diameter of

the seeds can presented as the arithmetic mean and geometric mean of the three axial

dimensions. Mohsenin, (1986) calculated the geometric mean diameter (Dg) and the

arithmetic mean diameter (Da) as follows:

Dg = (LWT)1/3 -----------------------------------------------------------------------------------------2

𝐷𝑎 = 𝐿+𝑊+𝑇

3 ----------------------------------------------------------------------------------------3

Mohsenin, (1986) also determined the shericity seeds by using the following equations:

ᶲ =(𝐿𝑊𝑇)

𝐿

1/3 -------------------------------------------------------------------------------------4

Whereᶲ is the sphericity; L is the length in mm; W is the width in mm; and T is the

thickness in mm. More over According to Razavi and Milani,(2006) the porosity which is

the ratio of free space between grains to total of bulk grains and coefficient of static

friction are determined as follows respectively:

휀 =𝜌𝑘−𝜌𝑏

𝜌𝑘 -----------------------------------------------------------------------------------------5

Where, ԑ is porosity

𝜌𝑘 is true density and

𝜌𝑏 is bulk density

𝜇 = 𝑡𝑎𝑛𝜑 --------------------------------------------------------------------------------------------6

Where, 𝜇 is coefficient of static friction

𝜑 is inclination angle

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2.4.Function of Seeders

According to Karayel and Ormerzi (2007) the success of cultivating a crop is strongly

related to the seeding process. In this process the machine factor has special importance,

since it is responsible for the spatial distribution of plants which in turn greatly affects the

productivity of crops. The overall functions of a planter are according to Kepner et al.,

(1982) to open the seed furrow to the proper depth, meter the seeds in a furrow in an

acceptable pattern, cover the seeds and compact the soil around them. In the precision

seeding the metering device allows the placement of seeds at pre set distance among them

in the furrow.

Seeders and planters are essential for the sowing of seeds. Their function is metering and

placing in the soil of seeds or plants or of parts thereof. Thus, seeders are used for

generative reproduction, whereas planters aid in vegetative propagation. In some parts of

the world, the term planter is used for a seeder. Both seeders and planters are either used as

solo machines or in combinations with preceding soil cultivating machines. In some cases,

combinations with fertilizing equipment are also common (Heege and Billot, 1999).

2.5.Seed Metering Devices

When a crop is planted, the aim is to establish plant population whose spacing contributes

to the maximum return per surface area Kepner et al., (1982). Optimizing the density of

plant is a prime importance, and this requires precision in terms of seed metering and

distribution by the seeding machine. The objective of seed metering is accurate and

uniform seeding without causing damage to the seeds.

Moreover, Herbek and Murdock (2003) reported that planting method should be based on

planting equipment, time and labour availability, seeding costs, planting date opportunity,

weather, crop usage, yield goals, and stand establishment risks associated with each

method. In addition, calibration of planting equipment is critical to getting the correct

number of seeds in the soil.

Seed distribution refers to the planting of seeds according to pre determined pattern

(Karayel and Ormerzi, 2007). This should take in to account the requirement for

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equidistance spacing between seeds. The depth at which they are planted should be

adjusted to provide them the best moisture condition (Kumar, 1989), it is therefore

important to take in to account the components of the drill and the possibilities of their

adjustment.

Karayel and Ormerzi, (2007), also reported that one factor affecting the quality of the crop

in mechanized crop production systems is the planting operation. The more precise the

planting operation, the better the quality of crop harvested. Precision planting reduces seed

scattering and excessive use of seeds due to uniform distribution of seeds and by

preventing seed from bouncing in the furrow, which facilitates drill calibration on the basis

of the number of seeds to be placed along a unit length of the row. Uniform germination

and growth of plants makes the subsequent operations, such as weeding and harvesting,

easy with less costs.

According to Karayel and Ormerzi (2007) the seed metering device is not only responsible

for the planters‘ performance concerning precision. The metered seeds still have to be

carried to the bottom of the furrow (opener at a certain depth) and properly conditioned.

The quality of these operations decisively affects the seedling emergence index (number of

viable seeds delivered to the emerged seedling ratio), which is one of the parameters used

to evaluate the final performance of a precision planter (Yadav et al., 2002)

Metering mechanism is the heart of sowing machine and its function is to distribute seeds

uniformly at the desired application rates. In planters it also controls seed spacing in a row.

A seed drill or planter may be required to drop the seeds at rates varying across wide range

(Zarate, 2004).

Yadav et al., (2002) described fluted rollers made of aluminium facilitate continuous

seeding of crops where control of plant to plant distance is not needed (wheat, rice, etc.).

Tooth size, depth of groove and the number of flutes depend on the seed size. For example,

there are 10 flutes in each roller for wheat seed. The rollers are fitted in a series on a shaft.

Aluminium cups are fitted on these rollers. Below the fluted rollers are aluminium or

plastic tongues to hold the seed. The tongues can be raised or lowered depending on the

size and texture (in case of rice) of the seed. As the fluted rollers turn, they push the seed

over the edge of the seed cups attached at the bottom of seed metering box which funnels

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Figure 2.2: Fluted Wheel Metering Device

the seed through the plastic seed tubes to the slit/furrow opener. In funnel shaped boot, a

deflector plate is provided for separation of seeds and fertilizer. A very precise seed rate

adjustment is obtained by sliding the fluted roller in or out. The more is the exposed area of

the fluted roller, the higher will be the seed rate and vice-versa.

2.6.Furrow openers

According to Stibbe et al. (1980) a furrow opener is an important component of a seed drill

or a planter. In general, a furrow opener cuts a furrow and allows the seeds or seedlings to

be deposited before being partially covered with soil. The types of furrow openers used

vary with soil and operating conditions. The common types of furrow openers used for

conventional tillage are hoe, shovel, shoe, runner, single disc, double disc, chisel and

inverted T furrow openers.

Several seedbed factors influence germination and emergence of crop under different soil

conditions. Many of these directly or indirectly affect the furrow opener design and, in

order to assess the performance of furrow opener, it is necessary to identify these factors.

Johnson and Buchele (1961) studied the effect of varying soil granule size and degree of

compaction on soil moisture loss and plant emergence in a sandy soil.

Experiments were conducted under laboratory conditions. A 0.18 mm soil granule in the

top layer showed a better moisture retention capacity as compared to size of 0.76 mm. For

a soil granule size of 0.18 mm, no compaction was necessary to improve plant emergence.

Thus, no press wheel was necessary for this size. Bateman (1963) investigated the effects

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of soil compaction on soil properties and found that a clay soil was susceptible to

compaction which caused high mechanical impedance to crop establishment. Thus, furrow

openers for clay soils should be designed for having loose soil above the seed. Stibbe et al.

(1980) investigated the effects of tillage on seedbed characteristics, plant establishment and

yield of maize on light sandy soil. Effects of furrow packing gave better emergence under

some conditions. However, additional compaction in the plant rows brought about a

significant decrease in crop yield. Panwar and Sirohi (1980) studied critical parameters of

plant emergence and root growth in sandy soil. They concluded that:

(a) a minimum soil moisture content of 10% is recommended for wheat and maize;

(b) for both wheat and maize, soil cover density of 1.3 and 1.9 g cm-3

proved to be too high

in soil impedance for plants to emerge;

(c) a seedbed density of higher than 1.5 g cm-3

restricted both root and plant growth; and

(d) the wheat crop was more sensitive to compaction as compared to maize

The most common design studies have been related to the optimum rake angle of furrow

openers. Furrow openers are generally of two types, one type with rake angles of less than

90° and the other with rake angles of greater than 90°. The effect of force on furrow

openers having different rake angles was studied by Dransfeld et al. (1964), Siemens et al.

(1965), Abernathy and Porterfield (1969), Gebresenbet and Johnson (1992), Mathur and

Pandey (1992) and Damora and Pandey (1995). Siemens et al. (1965) concluded

analytically as well as from experimental results that a rake angle of 25° gave the lowest

draught. The rake angle of the furrow opener which gave minimum specific draught was

reported by Mathur and Pandey (1992) as 28° for a lateritic sandy clay loam soil.

In addition to the effect of rake angle of the furrow openers on the forces acting upon them,

the rake angle also affects the depth of operation and the depth stability of the opener. The

depth stability is indicated by the variation in equilibrium depth of a seed drill furrow

opener due to changes in operating speed. Abernathy and Porterfield (1969) evaluated

runner-type furrow openers having rake angles ranging from 90 to 150° and horizontal

included angles (also known as the wedge angle) from 15 to 60° in a laboratory soil bin

containing light sandy soil. They reported that furrow depth was greater for openers with

large rake angles and large horizontal included angles. Gebrebenset and Johnson (1992)

reported that depth stability was best for a rake angle of 130° in a light sandy soil. No

conclusions, however, could be drawn for clay soils. Width of furrow openers is another

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design factor affecting draught of the opener as well as soil cover in the furrows of the

opener.

As reported by Siemens et al., (1965) and Gebrebenset and Johnson (1992), the force

acting on the furrow opener increases with increasing width of opener. The recovery of soil

in the furrows of the furrow openers of seeders for pre-germinated rice, operating in

puddled soil, was complete for furrow opener widths of 40 mm but not so for 50 mm

(Srivastava & Panwar, 1986). In order to account for variations in the horizontal and

vertical forces caused by changes in rake angle, width and depth of operation of furrow

openers, polynomial models were developed by Gebrebenset and Johnson (1992) for

furrow openers having rake angles ranging from 70 to 130°, depths ranging from 10 to 70

mm and width of opener ranging from 15 to 40 mm. These models were used to predict

rake angles for zero vertical force. The predicted rake angles ranged from 67° to 81°,

depending upon speed, depth and width of operation. However, the model could not be

extended to clay soils, as found from subsequent field studies.

2.7.Seed Covering Devices

Seed covering devices are specifically designed to promote soil flow back into the furrow

to cover the seed after placement and/or firming. They play an important role in promoting

and stabilising conditions conducive to rapid seed germination and influencing seed

emergence and establishment through the manipulation of the depth of soil cover over the

seed. The functional requirements of seed covering devices are to assist in the transfer of

displaced surface soil back into the furrow for the purpose of covering the seed with soil;

assist in regulating the depth of soil cover over the seed (i.e. assist in regulating planting

depth relative to the final seedbed surface); and in some cases, assist in re-levelling the

seedbed surface. (Zarate, 2004).

According to Murray et.al (2006), covering the seed with soil helps provide and stabilise

an appropriate seed environment (e.g. reduce the rate of moisture loss and provide

seed/soil contact to optimise both the rate of moisture transfer and the duration of moisture

availability to the seed, reduce temperature fluctuations, etc); and protect seed from

predators such as birds, mice and insects. The need for, and the design of, the covering

device on a planter depends on many factors, including the soil type and condition; the

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design of the furrow opener; the type and amount of surface residue; and the speed of

operation, etc. Not all planters have or need dedicated seed covering devices. Some drill

seeders, for example, rely solely on soil flow around the opener to cover the seed

2.8. Wheat Propagation and Planting

Belay and Brink (2006), reported that wheat reached North highlands of Ethiopia around

3000 BC. In tropical Africa durum wheat is predominantly grown in Ethiopia and to some

extent in Eritrea and Angola Wheat is propagated by seed. The 1000 seed mass of wheat is

30-50 g. It is advisable to use certified seed that has been treated with fungicides against

soil and seed-born diseases, but this is rarely practiced in tropical Africa. Wheat is sown by

hand or machine. When broadcasting, the seed is incorporated in the soil using an animal

drawn plough or machine drawn disc. The seed may also be dibbled directly into a furrow

behind the plough and covered, or machine planted in rows. Nelson, (1986) said that the

optimum seed rates for wheat vary with variety, location and method of planting. For seed

production fields, a lower seed rate may be recommended because lower seed rates lead to

higher multiplication factors but to lower yield per unit area. Higher multiplication factors

lead to rapid seed increase (more seed harvested per kilogram of seed planted), and farmers

will benefit from the improved variety earlier.

Low seed rates do not only increase the multiplication factor, but also often improve seed

quality because a lower number of plants per unit of land receive better nutrition, thus

producing better quality seed. Belay and Brink (2006) found that Common seed rates for

wheat are 150-200 kg/ha for broadcasting and 75-120 kg/ha for drilling in row. The

optimum spacing is 10-25 cm between rows, but it may extend up to 35 cm. The sowing

depth is 2-5 cm with deeper planting required in dry conditions

According to Herbek and Murdock (2003), best results in wheat stand establishment and

yield are obtained by seeding with a grain drill. A drill ensures good seed-to-soil contact,

promotes rapid germination, results in more uniform and optimum stands, reduces winter

injury, and increases yields over broadcast seeding and aerial seeding. Drills can be used

for conventional tillage, reduced tillage, and no-tillage field conditions. Conventional/full

tillage provides a level, smooth seedbed for drilling and results in a more uniform planting

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depth. Drills with additional coulters and more down pressure on the planter units can

establish a good stand of wheat in reduced tillage and no-tillage fields. Moreover, row-

planting with drills has an advantage over broadcasting, as it requires less seed and

facilitates mechanized weed control, roguing and field inspection. Roguing lanes (empty

rows at intervals) should be left, which could be used by the seed grower to walk through

the field when roguing and inspecting the crop, as well as for spraying the crop.

2.9. Use of Fertilizers

Fertilizer is defined as "any substance containing one or more recognized plant nutrient(s)

which is used for its plant nutrient content and which is designed for use or claimed to

have value in promoting plant growth" (AAPFCO, 1997).

Application of chemical fertilizers has played a pivotal role in increasing crop production

all over the world. The alkaline and calcareous soils of Pakistan are low both in nitrogen

(N) and in phosphorus (P), requiring the addition of nutrients in appropriate amounts for

improving crop yields. Consequently, the use of N and P fertilizers increased many fold

since their introduction in the late fifties (Ahmad, 2000). Nitrogen demand increased

consistently and outstripped that of phosphate, thus leading to a serious imbalance in the

use of these two nutrients. It is very well known that balanced fertilization helps efficient

utilization of other agricultural inputs and increases crop yields (Rashid, 1994; Alam et al.,

2000). Among other agronomic practices that influence the efficiency of applied fertilizer,

time and method of application are also critically important. As fertilizer is a costly input

and the fertilizer use efficiency under local soil and climatic conditions are low, maximum

use efficiency should be the target for high economic returns.

Ascher et al. (1994) concluded that fertilizer application to seed crops should be based on

local recommendations. A well balanced supply of nitrogen, phosphorus and potassium

(NPK) is essential for seed production as it has an influence on seed development and

thereby on seed quality. Phosphorus is essential for enhancing seed maturity and K for

seed development.

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2.10. Fertilizer Application Techniques

Several studies have been conducted to determine whether surface application or

incorporating controlled-release fertilizer (CRF) produces larger plants. Plant growth

varies depending on the method of application, nutrient release characteristics of the CRF,

rate of fertilization, container medium and plant species (Eakes et. al., 1990, Yeager et. al.,

1989).

According to Hairston, (2001), to minimize nutrient losses to the environment from

fertilizers, farm managers must ensure that plants use fertilizer efficiently. Best

Management Practices regarding fertilizer application techniques to increase fertilizer

uptake efficiency include proper timing, rate, and placement. Timing of fertilizer

application may be the most critical factor in determining fertilizer uptake efficiency and

crop yield. This is especially true for nitrogen fertilizer. When fertilizer is applied near the

time of maximum growth, crops are able to use more efficiently the nutrients. The more

nutrients that are used, the less opportunity there will be for loss. Extra amounts of

fertilizer will not ensure better crop yields or more efficient fertilizer uptake. Excessive

application will increase both the cost to the grower and the potential contamination of

surface waters and groundwater

Des Moines, (1989) discussed four different types of fertilizer placement (application) methods:

2.10.1. Broadcast and Surface Incorporation

The simplest method of fertilizer application is to broadcast the material on the soil

surface. The objective is uniform distribution of the nutrients and proper distribution of the

herbicide if a weed-and-feed combination of herbicide and fertilizer is used. Depending on

the tillage system, crop, expected weather conditions, herbicide program, and soil type, the

fertilizer material may be left on the surface or incorporated after application. So,

according to his finding, Des Moines (1989) reported that all nutrients will be more

efficiently utilized if they are incorporated after application. Incorporation makes the

nutrients less susceptible to erosion and runoff loss just after application.

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2.10.2. Banding

Applying fertilizer in a narrow zone or band to provide a concentrated source of nutrients

is an advantage under some situation. Humenik et.al., (1982) pointed out the banding

application may result in more efficient use of the nutrients (1) if soil test levels are low,

(2) when early season stress from cool or wet conditions is likely to limit root growth, (3)

where large amounts of surface residue limit soil-fertilizer contact, or (4) in soils that have

a high tendency to fix nutrients in unavailable forms throughout the soil

2.10.3. Starter

Starter fertilizer application, a form of band application close to the seed, is an important

means of getting crops off to an early start. It is particularly helpful for crops planted in

cool soils. Crops planted under conservation or reduced tillage conditions frequently face

those conditions. Cool soil temperatures slow root development, lower plant metabolism,

and diminish the amount of energy released by sugar metabolism, which is needed for

nutrient uptake. (Des Moines, 1989)

2.11. Machinery for Fertilizer Application

Hartley (1999) discussed machinery for fertilizer application varies, depending on

conditions under which fertilizer is applied and type of fertilizer. Machinery for fertilizer

application can be grouped into three categories, depending on mode of application:

• ‗Straight‘ spreaders ranging from large machines to tractor mounted units

• ‗Placement‘ machines which distribute the fertilizer onto the ground surface in

bands near the plant or just below the ground surface

• Liquid or gas application machines

When designing fertilizer application systems, various factors require consideration like

uniformity of distribution at both low and high speeds, accurate control of delivery rates

mechanical durability, easy operation, and rapid clean up.

18

3. MATERIALS AND METHODS

This study was carried out with an aim to modify and test an appropriate wheat drilling

machine. The drill was modified in order to evaluate its performance. Thus the study was

divided into two phases; machine modification and performance evaluation in the

laboratory and in the actual field. This chapter solely deals with modification and

fabrication of the wheat drill machine with fertilizer application capability and the

laboratory and field test procedures.

3.1. Location of The Study

All the mechanical works like machining, welding, etc, during the fabrication of the

machine were done at Adama Science and Technology University, Mechanical

Engineering Department Work shop. After development of the machine, laboratory tests

were also done at the same department. Finally the machine field performance tests were

also performed with in the campus experiment field. The soil of the area is categorised as

sand soil, the altitude is about 1500 m above sea level with annual rain fall ranging from

700-1200 mm as sourced from local meteorological station.

3.2. Material

The wheat drill machine consists of: the hoppers, seed metering devices, ground wheels,

seed and fertilizer tubes, furrow opening and covering devices, drive shaft, main frame and

the handle.

(a) The hoppers: - There are three feed hoppers for both wheat and fertilizer made of 2

mm thick mild steel with partition wall, each having a tapered cross section. The design

capacity of each hopper is 3 kg. The dimension of the hoppers is 280 mm x 270 mm x 170

mm.

(b) Seed Metering device: - The seed metering devices or flutes were made of aluminium

bar, turned by lathe machine to the required diameter and half cylindrical flutes were made

by milling machine. On each roller there are ten half cylindrical cells made, equidistant

19

from each other along the periphery. The dimensions of the cells are 10 mm diameter and 4

mm between consecutive cells.

(c) Drive wheels: - The drive wheels are made of mild steel and are integral parts of the

seed metering mechanism. The wheels drive a 20 mm internal diameter mild steel shaft

which is supported by two ball bearings on each side. The shaft transmits drive from drive

wheels to turn seed metering devices. The diameter of the wheels is 30 cm. Iron lugs were

welded to the wheel around its periphery to reduce slippage.

(d) Seed tube:- The seed tubes essentially have circular cross section made up of 2 mm

thick mild steel pipe that drop seeds directly in to the furrow.

(e) Furrow opening device: - The furrow opener is a 40 mm angle iron with a length of 88

mm. The angle iron is slightly bevelled at the lower edge to facilitate an easy cut through

the soil. It was attached to a 145 mm long square pipe shank which is welded to the main

frame of the machine.

(f) Furrow covering device: The furrow-covering device is made of a 1.5 m long mild

steel chain. It was attached to the hooks welded on the main frame of the machine at both

sides.

(g) Handle: The handle consists of two mild steel pipes of 20 mm internal diameter and 25

mm external diameter each of length 1150 mm. A crossbar, 800 mm long, was welded

through the upper sets of the two handles.

One of popular varieties of cleaned Bread Wheat (Triticum aestivum L. em Thell.) was

obtained from Melkassa Agricultural Research Center for the test. The initial moisture

content of seeds was determined by oven method (Tabatabaeefar, 2003). Granular fertilizer

required for the test was bought from local market.

20

3.3. Determination of Physical Properties of wheat.

3.3.1. Moisture Content

Wheat seed was bought from the local market and cleaned to remove foreign materials

and impurities. The moisture content of the seed as brought from the market was

determined by drying samples in an air circulating oven set at 105°C (± 2) for 24 hrs.

Then the moisture content was calculated using equation 1.

3.3.2. Average Size

The average size was determined based on 100 randomly selected seeds. Three linear

dimensions (namely, length L, width W and thickness T) of the seeds were measured using

digital vernier caliper with an accuracy of 0.01 mm. The average diameter of the seeds was

presented as the arithmetic mean and geometric mean of the three axial dimensions. The

geometric mean diameter (Dg) and the arithmetic mean diameter (Da) were calculated for

the three principal dimensions equations 2 and 3 respectively and sphericity of the seeds

was determined using equation 4.

3.3.3. Emptying Repose Angle.

A box made of sheet metal with the top and bottom having equal dimension of 300 mm by

300 mm, and a height of 400mm was used to measure the angle of repose. At 200 mm

from the top, a circular disc of 100 mm diameter was fixed so that enough gap was left

between the hopper wall and disc which allows the seeds to flow through during the test. A

horizontal sliding gate was provided right below the disc for sudden release of the seed

during the test. Similar device was used for green gram by Nimkar and Chattopadhyay,

(2001) and for teff by Zewdu and Solomon (2007).

21

Figure 3.1: A device for measuring emptying angle of repose

1. Circular disc

2. Steel box

3. Handle

4. Sliding gate

While testing, seed was filled in the hopper and the horizontal sliding gate was suddenly

opened. The height of seed piled on the circular disc was measured and used to calculate

the emptying repose angle 𝜃 using the formula:

𝜃 = 𝑡𝑎𝑛−1 𝑕

𝑟 --------------------------------------------------------------------------------------------7

Where, h is the height of piled seed in mm, and r is the radius of the disc in mm.

3.3.4. Bulk Density

The bulk density was measured by pouring the seeds in stainless-steel cylinder of known

volume and mass, 81.7 ml and 90.6 g respectively and removing excess seed by rolling

cylindrical glass rod on the ream of the container without compacting the seed. Each time

the wheat was weighed, the mass of empty container was subtracted from the total mass to

know the mass of grain contained within the container. The mass of seeds filled in the

cylinder divided by the volume of cylinder gave the bulk density. True density was

determined as the ratio of sample mass to the true volume of the seeds using toluene

displacement method.

22

3.3.5. Coefficient of Static Friction

The coefficient of static friction 𝜇 was determined for wheat seed against mild steel

surface. A plastic cylinder of 75 mm diameter and 50 mm height was filled with sample

and placed on tilting table having a scale to read the tilting angle directly. The seed-filled

cylinder was raised slightly, so that it will not have contact with the surface. The table was

raised gradually using a screw device till the cylinder just started to slide down and the

corresponding tilting angle 𝜑 was recorded. The value of 𝜇 was calculated using equation

6. Porosity is the ratio of free space between grains to total of bulk grains. That was

computed using equation 5.

3.4.Modification of the Seeder

The rice hill seeder to be modified is shown below:

Figure 3.2: The seeder to be modified with its metering disc.

The seed hopper, seed metering device, furrow openers, ground wheel and fertilizer

metering device were modified as stated below.

3.4.1. Seed Hopper

The seed and fertilizer hoppers were fabricated to cover almost full width of the machine.

These boxes were located above the main frame and fabricated with two millimetre thick

structural steel sheet. Partition was provided along the whole length of the box to avoid

direct contact of seed and fertilizer. Cross sectional area of the hopper was determined by

considering its trapezoidal section with ‗B‘ as base width, ‗h‘ as height of section and ‗α‘

as emptying angle of repose of wheat (RNAM, 1995).

23

)cot( hBhA -------------------------------------------------------------------------------------8

Where, A is cross sectional area of the hopper

h is height of the section

B is base width of the hopper

α is emptying repose angle

Fig 3.3: Sketch of the hopper with partition wall

3.4.2. Seed and Fertilizer Metering Devices

The previously used stainless steel metering disc with cells around its peripheral was

modified to fluted rollers seed metering device that were made from aluminium bar. The

diameter of the aluminium bar was brought to the calculated diameter of the rollers by

turning it on lathe machine and the flutes (grooves) on the roller were cut by milling

machine. There are ten flutes (grooves) cut around the circumference of the roller with the

spacing between each is 5mm. Based on RNAM (1995), which recommends 8-12 flutes,

seed metering device containing ten flutes was selected.

According to RNAM (1995), with pre determined seed rate and row spacing, the exposed

length of fluted roller to drop seed was determined with the following equation:

𝑙𝑓 = 8×𝑠×𝑟𝑥𝑑𝑔

10×𝜌𝑏×𝑑𝑓

2×𝑁𝑓×𝑖---------------------------------------------------------------------------- 9

Where, lf is length of fluted rollers s is seed rate in kg/ha ,

24

ρb is bulk density in kgm-3

,

r is row spacing in m,

df is diameter of flute in m,

Nf is number of flutes,

i is transmission ratio and

dg is diameter of ground wheel in m,

The diameter of fluted roller plays an important role in dropping measured quantity of seed

per unit area. The diameter of fluted roller (dr) according to Muhammad (2004) was

determined with the help of the following relationship:

)( fff

r

sdNd

---------------------------------------------------------------------------------10

Where, Nf is number of flutes,

df is diameter of flutes in m and

sf is spacing between flutes in m.

The grooves cut through the length of the seed metering aluminium rollers were half

cylinders and their volume was determined as follows:

𝑉 =1

2𝜋𝑟2𝑕 ----------------------------------------------------------------------------------------11

Where, 𝑉 is volume the flute

r is radius of the cylinder and

h is the length of the groove

Both seed and fertilizer metering units were installed on the same shaft side by side. Two

flat mild steel wheels having 40 cm diameter each, were provided on either side of the

25

machine. The drive is transmitted directly from wheels to the shaft on which the seed

metering units are mounted. Lugs were welded around the circumference of the wheel to

reduce slippage of the drive wheels.

Fertilizer metering device was required to meter and drop fertilizer from fertilizer box into

the furrow. The placement of fertilizer in furrows was adopted in order to reduce

volatilization loss of nitrogen. The fluted wheel metering devices made from aluminium

were incorporated because of their capability for easily handling granular fertilizer

(RNAM, 1995). The procedures used to modify the seed metering device were used to

modify fertilizer metering device.

3.4.3. Seed and Fertilizer Placement Mechanism

3.4.3.1.Furrow Opener

A furrow opener should make a narrow slit with least soil disturbance and promote plant

emergence by maintaining edaphic factors such as moisture content, bulk density, aeration

and temperature so that the root bed is conducive to seed germination. The share of the

furrow should be sharp and wear resistant.

Keeping in view the above requirement the hoe type furrow openers made of steel angle

iron were employed. The furrow openers of these types has lower draft requirement when

compared with shoe type and shovel type openers according to Benjaphragairat et al.,

(2010). The furrow penetration depth of 2-5 cm which is recommended for wheat was

considered during the modification of the furrow opener and was made 3.5 cm

The furrow openers were welded on straight shanks made of mild steel. The rake angle of

the openers was made 20 degrees in order to facilitate the working of furrow openers with

minimum of soil disturbance. The relief or clearance angle was also made 20° in order to

minimize draft (Kepener et al.,1982).

26

3.4.3.2.Furrow Covering Device

Even though the wide range of seed covering devices exist, a Chain type covering device

was used to trail behind the furrow opener and drag loose soil into the furrow to cover the

seed. Chain type covering devices are most easily adapted for use in well-prepared (friable)

seedbeds without significant quantities of surface residue and where no significant degree

of soil movement is required to fill the furrow (Murray et al. 2006). Therefore 1.5 m long

chain was attached to hooks welded at either ends of the machine to be used as furrow

covering device

3.4.3.3.Seed and Fertilizer Tubes

Releasing of both seed and fertilizer through the same tube is not good practice (Smith,

1965). A better method is to release the fertilizer through separate tubes. In order to drop

the seeds and fertilizer through separate tubes a pipe was provided behind each furrow

opener.

Direct contact of seed with fertilizer affects seed germination, therefore a partition wall

provided in each furrow opener helped to exclude that possibility. Separate furrow openers

for seed and fertilizer were not provided because they would have increased cost of

machine and draft requirement.

3.5. Design of Power Transmission Shaft

In order to design the power transmitting shaft, the parameters taken into account were the

speed of the shaft, power to be transmitted, torque applied on the shaft and bending and

twisting moments on the shaft. The speed of the shaft and power transmitted by the shaft

were 20 rpm and 156 W respectively. To measure the rpm of the shaft the ground wheel

was painted and the machine was operated at normal walking speed. Then the stop watch

was used and the number of the ground wheel turns in one minute was recorded. Finally

the rpm of the shaft was determined by multiplying the rpm of the ground wheel with the

transmission ratio (diameter ratio) of the two components. The maximum bending moment

was worked out to be 8.1 N-m. As the shaft was to be subjected to fluctuating loads, the

27

equivalent twisting moment (Te) and equivalent bending moment Me were determined to

find the internal and external diameters of the hollow shaft.

The required outer and inner diameters of the hollow shaft were found to be 25 mm and 20

mm respectively. The detailed procedure for the design of the shaft is shown in Appendix

A.

3.6. Laboratory Tests of the Seeder

3.6.1. Seeding Rate Test

This test was done to check whether the machine is accurately dropping seeds in

accordance with the pre determined rate or not. After this test is done if the seeding rate is

above the pre determined rate, it will be corrected by reducing the length of the seed

metering unit exposed to the seeds dropping from seed hopper until the correct rate is

recorded and if the rate is below the pre determined rate it will be corrected by exposing

more length of the seed metering roller until the recommended rate is obtained.

To do this the diameter of the wheel, D, was measured and multiplied by π to determine its

circumference C, i.e.

𝐶 = 𝜋𝐷 ------------------------------------------------------------------------------------------------12

Then the distance L to cover one hectare was determined by dividing the area of one

hectare, 10,000 m2 for the effective width W of the machine in meter i.e.

𝐿 =10,000 𝑚2

𝑊 ------------------------------------------------------------------------------------------13

For this test one hundredth of the hectare length l was taken as sample and the result

obtained was multiplied by hundred for the whole hectare. Therefore to cover distance l the

wheels of the machine should turn n times,

𝑛 =l

πD . ----------------------------------------------------------------------------------------------14

Allowing 10% slippage the distance l can be covered in N turns i.e.

28

N = n − 0.1n . -------------------------------------------------------------------------------------15

After N is known, the wheels that drive the machine metering unit was elevated so it

didn‘t contact the surface and was turned N revolutions. Finally, the total seed dropped

under the seed drill was collected and weighed. And thus the seed rate per hectare was

calculated and compared with the pre determined rate (Yadav et al., 2002).

Figure 3.4: Seeding rate test in the lab.

3.6.2. Seed Damage Test

When the metering device is operating and discharging seeds, there might be some seed

damages. The damage is either visible physical damage or internal damage. The physical

damage can easily be observed, but to know the extent of internal damage germination test

should be conducted. Therefore; germination test was done by using seeds discharged from

each tube of the machine in the laboratory.

To obtain sample for testing, a total of 300 sample grains, and 100 from each seed tube

were taken randomly. The sample seeds were then put in row for ease of counting in the

moist soil contained by three water proof trays. The Seeds were sown at normal seeding

depth of 2-5 cm placing them on top of the soil and pushing in with a piece of dowel and

covered with a little more soil. The tray was watered gently to keep it moist (not wet)

29

since Over-watering results in fungal growth on the seeds, causing possible seed rot,

affecting normal germination. Seedlings were counted after 5 to 10 days when the majority

of seedlings are up. Here it is not necessary to wait until the late ones emerge–these are the

damaged weak ones, and finally the germination rate was determined calculated by using

the following equation(Chang, 1988).

𝐺𝑒𝑟𝑚𝑖𝑛𝑎𝑡𝑖𝑜𝑛 (%) = 𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒔𝒆𝒆𝒅𝒔 𝒈𝒆𝒓𝒎𝒊𝒏𝒂𝒕𝒆𝒅

𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒔𝒆𝒆𝒅𝒔 𝒐𝒏 𝒕𝒓𝒂𝒚× 100 -------------------------------------------16

3.7. Field Tests

Field performance tests were carried out to obtain actual data on the overall machine

performance. The machine field performance was evaluated by determining its draft force

requirement, field capacity and field efficiency. The field test was prepared to create an

optimum condition for proper test of the machine. A 2000 m2 (200m*10m) plot of land

was prepared in the compound of Adama Science and Technology University main

campus. The machine was tested on a well prepared seed bed.

3.7.1. Determination of Soil Moisture Content

Soil moisture content, which affects the draft force requirement to operate the machine,

was determined by dry weight basis. The soil samples were taken from the test plot, at a

depth of (2, 3.5, 5cm), the electrical balance was used for measuring the soil samples. The

samples were placed in oven at 1050

C for 24 hours. The dried soil samples were re-weighed

in an electrical balance and the weight was recorded. The soil moisture percent (% dry

weight basis) was calculated using the following formula, RNAM, (1995).

100

d

dw

W

WWMC ------------------------------------------------------------------------------17

where, MC is Moisture content (%), Ww is Weight of wet soil (g), Wd is Weight of dry soil

(g).

3.7.2. Determination of Draft Force

Even though a number of different methods exist to measure the draft force requirement of

the machine, a spring balance method was selected suitable for this work. The machine

was taken to the test field, while operating, the machine was stopped and its handles were

30

cut while the furrow opener was still in the soil at some depth. A spring with known initial

length (free length) was inserted between the cut handles and stacked together with the

handle by sticking material called epoxy resign.

The greater change in length of the spring was recorded when the machine was just starts

to roll when operated. Hence, the maximum change in length of the spring was taken to

determine the draft force requirement of the machine.

The spring was then taken to the valve spring compressor and compressed to the length the

seeder compressed it while it was between the cut handles of the machine and the force

(kgf) that is used to compress the spring was recorded as the draft force requirement of the

machine.

3.7.3. Machine Field Capacity and Field Efficiency tests

Machine field capacity can be evaluated from two different angles, the first one is the

theoretical field capacity of the machine in ha/h. It depends only on the full operating

width of the machine and the average travel speed in the field. It represents the maximum

possible field capacity that can be obtained at the given field speed when the full operating

width of the machine is being used.

Here the important parameter that evaluates the field capacity of the machine is its

effective field capacity not the theoretical one. But the effective field capacity was

determined from the theoretical field capacity of the machine. The effective field capacity

(EFC) is expressed as the rate at which it can do work, taking into account such non

productive operations as turning at the ends of the field, stopping to add seed or fertilizer,

stopping to check performance and the amount of overlap into previously travelled area.

Before determining the effective field capacity of the machine the field efficiency of the

machine was required to be known.

According to Lacayanga et al., (2009), theoretical Field capacity of the seeder, C can be

determined as follows.

WSC ---------------------------------------------------------------------------------------------18

31

Where, C is theoretical field capacity (ha/h), S is forward speed (m/s) and W is width of

the machine (m).

To determine the forward speed S, the length of the field which was already determined 20

m was taken as a distance for a pass, a stop watch was used to know time required to

complete the 20 m. Then the speed of each pass was determined by simple mathematical

relations,

𝑠 =𝑙

𝑡 ---------------------------------------------------------------------------------------------------19

Where, 𝑠 is velocity, 𝑙 is the distance travelled and 𝑡 is the time taken

Five treatments were done and the speed obtained by each treatment was multiplied by the

width of the machine which was measured 60 cm to get its theoretical field capacity.

Finally, the mean value was taken as the theoretical field capacity of the machine.

Von Bargen and Cunner, (1974) defined field efficiency, e as the primary activity time (the

time the machine is operating in the field at an optimum forward speed and performing

over its full width of action) divided by the sum of all field activities, shown as

𝑒 =𝑡𝑝

𝑡𝑝+ 𝑡𝑖𝑛𝑖=1

------------------------------------------------------------------------------------------ 20

Where, e = field efficiency, 𝑡𝑝 theoretical field time and 𝑡𝑖 other activity time

The field efficiency of the machine was determined from the data obtained while planting

the given plot of land. The total time required to complete 200 m2 was taken as both tp and

ti. That means ti was recorded as the time including turning at head lands, to refill the seed

and fertilizer hoppers and other machine check up and preparation time. After the

determination of field efficiency, the effective field capacity was determined as follows:

𝐸𝐹𝐶 = 𝑇𝐹𝐶 × 𝑒 -------------------------------------------------------------------------------------21

Where, 𝐸𝐹𝐶 − Effective field capacity (ha/h)

3.8.Data Collection

Most of the data collected were related with machine performance tests both in the

laboratory and actual field conditions. For seeding rate test in the laboratory, the diameter

and rpm of the ground wheel and the machine width were taken as the data and for the seed

32

damage tests sample seeds from each seed tube were taken randomly. Machine forward

speed, machine width and the time taken in test field were the data collected for

determination of the field capacity and field efficiency of the drill machine. Compression

spring deflection and load on the spring were the data collected for determination of the

draft force requirement of the machine. Statistical method of data analysis was used for all

cases to measure data.

33

4. RESULT AND DISCUSSION

4.1 Physical Properties Wheat Grain

The mean dimensions of about 50 samples at moisture content of 9.71% d.b were: length

6.25 mm, width 3.35 mm and thickness 2.75 mm. All dimensions were increased with an

increase in moisture content from 9.71% to 17% w.b. The increasing trend in axial

dimensions, with gain in moisture content, was due to filling of capillaries and voids upon

absorption of moisture and subsequent swelling.

One thousand kernels weight was 21.35 g. The sphericity of grains was found 0.59 and the

mean volume of a grain was found 31.74 mm3. The geometric mean diameter was 3.91 mm

and the arithmetic diameter found 4.2 mm at 9.71% d.b.

The value of bulk density and true density were 987 kgm-3

and 1240.5 kgm-3

respectively.

Moreover, the porosity of the wheat grains was calculated to be 20.4%. The static

coefficient of friction on sheet metal surface was 0.47 and the emptying repose angle found

to be 34°. at 9.71% d.b.

A linear increase in the one thousand kernel mass as seed moisture content increased has

been noted. TGW increased linearly from 21.35 g to 34 g when the moisture content

increased from 9.71to 17 % d.b.

The sphericity of wheat grains increased from 0.63 to 0.66 with an increase in moisture

content. The geometric mean diameter of wheat grains increased from 3.96 to 4.25 mm and

arithmetic diameter from 4.1 to 4.4 mm. The values of the bulk density for different

moisture levels varied from 987 to 789 kg m-3

. The true density varied from 1240.5 to

1185.5 kgm-3

when the moisture level increased from 9.71% - 17% d.b. The porosity of

wheat grains increased significantly from 0.24 to 0. 33 with the increase in moisture

content from 9.71% to 17%. It was observed that the static coefficient of friction on iron

sheet metal increased with increase in moisture content. This is due to the increased

adhesion between the grains and the material surfaces at higher moisture values.

34

Table 4.1: Summary of the physical properties of wheat as it varies with moisture content

MC(%) L

mm

W

mm

T

mm

ρk

kgm-3

µ R*a

Deg.

9.71 6.25±0.38 3.35±0.35 2.75±0.23 1240.5±0.25 0.47±0.022 34±0.62

12 6.29±0.39 3.45±0.45 2.85±0.25 1202±0.26 0.55±0.023 36±0.65

17 6.45±0.42 3.70±0.33 3.05±0.22 1185.5±0.29 0.58±0.027 41±0.67

R*a – angle of repose

4.2. The Modified Seeder

The seeder is basically manually operated by only one person. The wheel is the driving

mechanism that allows the metering device to turn as the shaft turns. As the seeder is

pushed forward, the seed in the hopper drops on to the flap below the seed metering device

and fills the gap between the seed metering device and the flap. The seed metering device

then guides the seed from the underneath flap into the seed tube fixed below it. This allows

the seeds to be delivered to destination furrow. Turning on headland is simply

accomplished supporting the weight of the machine on the stand provided. This action does

not discharge seeds because the wheel is suspended and there will be no drive transmitted

to the seed metering device.

35

(a) (b)

Fig 4.1: Sketch of the modified machine: (a) front view, (b) side view

1. Ground wheel 6. Handle

2. Seed hopper 7. Furrow opener

3. Fertilizer hopper 8. Seed tube

4. Drive shaft 9. Furrow covering device

5. Main frame 10. Fertilizer tube

Fig 4.2: Isometric view of the seeder

36

4.3. Evaluation of Seeding Rate

The machine was required to seed wheat at a rate of 120 kg/ha. This pre determined rate is

achieved by the proper design of seed delivering components of the drill machine specially

seed metering units. Therefore, to check whether the intended outcome was achieved or

not seeding rate test was performed in the laboratory (p value < 0.0001). Hence, after

turning the suspended wheels 120 times seeds dropped under each seed tube were collected

and weighed.

Table 4.2: Mass of grain discharged from each seed tube

Seed tube Weight (kg)

Seed tube 1 0.41±0.0065

Seed tube 2 0.42±0.006

Seed tube 3 0.41±0.0055

Since the seeding rate test was done for 1/100th

a hectare, multiplying the total mass of

seeds collected by 100 gives the amount of wheat seed required in kg for 1 hectare of land.

Therefore, 124 kg/ha was the result obtained from the data which is within the

recommended range of seeding rate for wheat. The variation seen among the output from

the three seed tubes tabulated above was negligible to consider.

Table 4.3: Varying seeding rate

Length (mm) Rate (kg/ha)

10 82.5±0.27

11 90.95±0.28

12 99.2±0.26

13 107.5±0.26

14 115.75±0.25

14.5 120±0.27

37

Figure 4.3: Rate vs length of seed metering device

4.4. Evaluation of Fertilizer Application Rate

The machine was designed to apply fertilizer at a rate of 100 kg/ha. This pre determined

rate is achieved by the proper design of seed delivering components of the drill machine

specially fertilizer metering units. Therefore, to check whether the intended outcome was

achieved or not test of fertilizer application rate was performed and the result of the test

was compared with the pre targeted one. The procedure used to test the application rate of

fertilizer was the same with that of used for testing the wheat seeding rate.

Therefore, after turning the suspended wheels 120 times, as determined before and

fertilizer grains dropped under each fertilizer tube were collected and weighed.

Table 4.4: Mass of fertilizer discharged from each tube

Fertilizer tube Weight (kg)

Tube 1 0.35±0.024

Tube 2 0.37±0.023

Tube 3 0.31±0.025

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12 14 16

Rat

e (

kg?

ha)

Seed metering device length (mm)

38

Multiplying the total weight of fertilizer collected by 100 gives the amount of fertilizer

required in kg for 1 hectare of land. Therefore, 103 kg/ha was the result obtained from the

data. Like for wheat, fertilizer application rate can be adjusted to any desired rate by

adjusting the length of the fertilizer metering device exposed to the opening of the fertilizer

hopper.

Table 4.5: Varying fertilizer application.

Length (mm) Rate (kg/ha)

8 66±0.66

9 74.5±0.63

10 82.5±0.65

11 91±0.64

12 99±0.62

12.5 103±0.67

13 107.5±0.65

Figure 4.4: Rate vs length of fertilizer metering device

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12 14 16

Rat

e (

kg?

ha)

Length of fertilizer metering device (mm)

39

4.5.Germination test assessments

Seed germination test result, which is an indication tool for the extent of the seed internal

damage caused by seed metering units, is one of the factors which determine the efficiency

of the machine .Germination rate was taken as the average number of seeds that germinate

over 10 days.

Figure 4.5: Germinated seeds on trays in the lab.

The result from the first seed tube shows that 87% of the seeds germinated in the first five

days and only 7% seeds germinated after the fifth day until the last 10 days and the results

from the second seed tube reveals that 93% the seeds germinated with in the first five days

and 4% seeds germinated at the end of the 10th

day. A result from the third seed tube shows

89% of the seeds germinated after the fifth day and 8% of the seeds found germinated at

the end of the 10th

.

Table 4.6: Percentage of germinated seeds up to 10 days

Seed tube % germinated in five days % germinated 6-10 days Total %

From 1st seed tube 87 7 94

From 2nd

seed tube 93 4 97

From 3rd

seed tube 89 8 97

Mean 89.67 6.34 96

40

Figure 4.4: Percentage of seed germinated depending on the number of days after seeding

Hence, as it can be observed from the result 96% of the seeds were emerged (average) and

be fairly enough as Peter and Holding (2005) found more than 80% should emerge.

4.6. Soil Moisture Content and Draft Force Requirement.

The result from the measurement of soil moisture content at (2, 3.5, 5cm) is shown below.

The values show that as the depth of the soil increases its moisture content increases

because of less exposure to sun light and air movement when compared with the upper

depths. The increase in moisture content further results in increase of bulk density of soil

which also results in high penetration resistance (great draft force requirement).

Table 4.7: Values of soil moisture content at different depths

Depth % of moisture

Moisture content at 2 cm depth 12±0.22

Moisture content at 3.5 cm depth 13.5±0.23

Moisture content at 5 cm depth 14.25±0.25

-20

0

20

40

60

80

100

0 1 2 3 4 5 6 7

%ge

rmin

ate

d

number of days

41

Figure 4.7: Soil moisture content vs depth

A compression spring with free length of 4 cm and 1.5 cm diameter was inserted between

the removed handles of the machine. The change in length (deflection) of the spring at the

moment the machine starts rolling, which is the maximum deflection was recorded 2.5 cm.

The spring was taken to the valve spring tension measuring device. A force was applied on

the spring by the machine until the same deflection is attained when it was between the

handles of the machine.

Figure 4.8: Spring tension testing machine

Therefore, a force of 215 N was recorded to compress the spring to the same length

compressed by the machine and it was taken as the draft force requirement of the seeder.

10.5

11

11.5

12

12.5

13

13.5

14

14.5

2 3.5 5

Soil

mo

istu

re c

on

ten

t %

d.b

Soil Depth (cm)

42

Figure 4.9: Load vs deflection of the compression spring used for the test.

From the above figure we can observe that the stiffness of the spring (k) is equivalent to

the slope of the graph.

4.7. Field Capacity and Efficiency

To complete 2000 m2

(0.2 ha) plot of land it takes about 0.8 h. Hence, 0.8 h is theoretical

field time (tp) and 31% of the theoretical field time was measured to be wasted at land

heads during return and refilling hoppers, the other activity time, ti becomes 0.25 h. Then

by applying equation 7, the field efficiency, 76%, was obtained. Then the effective field

capacity according to equation 8 was determined and found to be 0.18 ha/h, that means if

the machine is operated for 5.5 h, it will complete 1 hectare which will take more than two

days (16 working hours) for the traditional method of broadcast sowing.

0

5

10

15

20

25

30

35

40

0 0.5 1 1.5 2 2.5 3

43

5. Conclusion and Recommendation

5.1. Conclusion

This study was under taken to modify and develop a machine which would drill wheat

seeds in row and fits the local farming needs. As a result of this study a manually operated

wheat row seeder machine with fertilizer applicator was developed with three row planting

unit. The spacing between rows was 20 cm. The power to seed metering devices was

provided from ground wheels through hollow shaft.

After completing the assembly of the machine, its laboratory and field tests were carried

out. The laboratory test includes seeding rate and seed damage tests. The seeding rate test

was performed in an intention to check whether the machine is seeding to the pre

determined rate (120 kg/ha) or not and the test result showed that the seeding rate was 124

kg/ha, which is within the recommended range of seeding rate for wheat (100-125 kg/ha).

The result obtained from the test of fertilizer application rate was 103 kg/ha, which can of

course be adjusted to any desired rate by changing the length of fertilizer metering device

exposed to the base of the fertilizer hopper.

The seed damage test was carried out to know the amount of internal and external damages

caused by seed metering units while discharging (metering) seeds to the underneath furrow

via seed tubes. The external damage was simple to observe it on the seeds discharged out

of the seed tubes, but germination test was carried out to evaluate the extent of internal

damages of the seeds. Accordingly, 100 seed samples were taken from the discharges of

each seed tubes randomly and put on wet soil tray for ten days. The result showed that

above 95% of the seeds germinated from each seed tube.

The machine was also tested in the actual field prepared in the University‘s test field for its

capacities and efficiency. The theoretical and effective field capacities were determined

and found to be 0.244 ha/hr and 0.18 ha/hr respectively. The field efficiency of the

machine was 76%.

44

The draft force requirement of the machine was determined by the spring balance method

and found to be 215 N, a push, which an average person can satisfactorily operate the

machine with less drudgery to push.

45

5.2. Recommendation

The developed wheat row seeder machine with fertilizer applicator is believed to improve

the yield of small holder farmers with better efficiency and additional seed saving

capability. Therefore, after appropriate trial, its dissemination to the smallholder farmers is

recommendable.

46

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51

APPENDIX A

Calculations for the design of power transmitting shaft

The shaft carrying three hoppers with wheat and fertilizer inside is like a simply supported

beam as shown below. The shaft is supported at A and B in roller bearings. It is a hollow

shaft made of mild steel required to transmit 156 W of power at 20 rpm. It carries three

hoppers each weighing 45 N with full of wheat and fertilizer. According to ASME code the

allowable shear stress and bending stress for none keyed commercial shaft are 45 Mpa and

100 Mpa. The diameter (internal and external) of the shaft can be determined as follows:

𝑃 = 156 𝑊

𝑁 = 20 𝑟𝑝𝑚

𝑇 =𝑃×60

2𝜋𝑁=

156×60

2×3.14×20= 74.5𝑁𝑚 = 74500𝑁𝑚𝑚

Where, P is the power transmitted

N is revolutions per minute of the ground wheel

T is the torque transmitted

The reaction at each support will be 67.5 N i.e.

𝑅𝐴 = 𝐴𝐵 = 67.5 𝑁

52

It can be observed that the maximum bending moment lies at point E and it is zero

at the reaction points.

𝐵𝑀𝐸 = 67.5 𝑁 × 0.27𝑚 = 18.22𝑁𝑚 = 18220𝑁𝑚𝑚

𝐵𝑀𝐶 = 0.07 × 45 = 4.725𝑁𝑚

𝐵𝑀𝐷 = 0.07 × 45 𝑁 = 4.725𝑁𝑚

𝐵𝑀𝐴 = 𝐵𝑀𝐵 = 0

Where, BM is bending moment.

Now let‘s determine the equivalent twisting moment and equivalent bending

moments to determine the internal and external diameters of the shaft:

𝑇𝑒 = 𝑀2 + 𝑇2 =𝜋

16× 𝜏(𝑑𝑜)3(1 − 𝐾4)

Where, Te is equivalent twisting moment

M is bending moment

T is torque transmitted

𝜏 is allowable shear stress =42 𝑁

𝑚𝑚 2 for the material selected

do is outer diameter

K is 𝑑𝑖

𝑑𝑜= 0.75

Therefore, 𝑇𝑒 = 18.222 + 74.52 = 76.7𝑁𝑚

Hence, 76700𝑁𝑚𝑚 =3.14

16×

42 𝑁

𝑚𝑚 2(𝑑𝑜)3(1 − 0.754)

𝑑𝑜 = 23.88𝑚𝑚 ≅ 24𝑚𝑚 and 𝑑𝑖 = 0.75 × 24𝑚𝑚 = 18𝑚𝑚

The equivalent bending moment (Me) is determined as:

𝑀𝑒 =1

2(𝑀 + 𝑀2 + 𝑇2 =

𝜋

32𝛿𝑏(𝑑𝑜)3(1 − 𝐾4)

53

Where, 𝑀𝑒 is equivalent bending moment.

𝛿𝑏 is allowable bending stress =100 𝑁

𝑚𝑚 2 for the selected material.

Hence, 𝑀𝑒 =1

2(18.2𝑁𝑚 + 18.222 + 74.52 = 47.44𝑁𝑚

Again, 47440𝑁𝑚𝑚 =𝜋

32𝛿𝑏(𝑑𝑜)3(1 − 𝐾4)

=3.14

32×

100 𝑁

𝑚𝑚2 (𝑑𝑜)3(1 − 0.754)

𝑑𝑜 = 20 𝑚𝑚 𝑎𝑛𝑑 𝑑𝑖 = 0.75 × 20 = 15 𝑚𝑚

Now we have two values for both 𝑑𝑜 and 𝑑𝑖 and the larger values for 𝑑𝑜 = 24 mm

and 𝑑𝑖 =18mm, but available stock size in the market, 25 mm for 𝑑𝑜 and 20 mm

for 𝑑𝑖 were taken for the machine.

54