Yield and water productivity of rice–wheat on raised beds at New Delhi, India

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Field Crops Research 100 (2007) 229–239

Yield and water productivity of rice–wheat on

raised beds at New Delhi, India

B.U. Choudhury a,b, B.A.M. Bouman c,*, A.K. Singh a

a Water Technology Center, Indian Agricultural Research Institute, New-Delhi 110012, Indiab Punjab Remote Sensing Center, PAU Campus, Ludhiana 141004, India

c International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines

Received 21 April 2006; received in revised form 24 July 2006; accepted 24 July 2006

Abstract

Permanent raised beds are being proposed for the rice–wheat system in the Indo-Gangetic Plain to increase its productivity and to save water. It

is not clear whether reported water savings in rice arise from the geometry of the beds per se or from the particular water management that keeps the

soil in aerobic conditions and that can also be applied on flat land. Moreover, little research has been reported on direct seeding of rice on raised

beds and on the effect of raised beds on the subsequent wheat crop. In this paper we compare the yield, input water (rainfall and irrigation) use and

water productivity of dry-seeded rice on raised beds and flat land with that of flooded transplanted and wet-seeded rice, and analyze the effects of

beds on the subsequent wheat crop. The experiment was conducted in 2001–2003 at New Delhi, India.

Rice yields on raised beds that were kept around field capacity were 32–42% lower than under flooded transplanted conditions and 21% lower

than under flooded wet-seeded conditions. Water inputs were reduced by 32–42% compared with flooded rice, but could also be accomplished with

dry seeding on flat land with the same water management. Reduced water inputs and yield reductions balanced each other so that water productivity

was comparable among most treatments. Wheat yield was 12–17% lower on raised beds than on flat land with conventional (20 cm) row spacing.

Neither wheat nor rice on raised beds compensated for the loss in rows by extra tillering or leaf growth at the edges of the rows. There was no carry-

over effect of type of land preparation in rice on the growth and yield of the subsequent wheat crop. Further research on raised beds should focus on

the selection of suitable rice and wheat varieties, soil health issues such as nematodes and micro-nutrient deficiencies, weed control, bed stability

and long-term carry-over effects from one crop to the other.

# 2006 Published by Elsevier B.V.

Keywords: Raised beds; Rice–wheat; Water productivity; Indo-Gangetic Plain

1. Introduction

In the Indo-Gangetic Plain of South Asia, the rice–wheat

(RW) cropping system covers an estimated area of 13.5

million ha, with some 10 million ha in India (Timsina and

Connor, 2001). Irrigated rice production has only recently

moved into this nontraditional rice-growing area and the major

expansion of the RW system occurred between the 1960s and

1990s. During these years, the production of rice and wheat was

supported by favorable policies such as subsidies for inputs and

minimum support prices for outputs (Barker and Dawe, 2002).

Private investment in groundwater pumping expanded the irri-

gated area, and short-stature, short-duration and high-yielding

* Corresponding author. Tel.: +63 2 580 5600; fax: +63 2 580 5699.

E-mail address: [email protected] (B.A.M. Bouman).

0378-4290/$ – see front matter # 2006 Published by Elsevier B.V.

doi:10.1016/j.fcr.2006.07.009

modern varieties of rice and wheat were introduced. Usually,

rice is transplanted into puddled soil and farmers try to maintain

ponded water on the surface throughout the cropping season.

This practice of (lowland) rice production alters the physical

structure of the soil which may have negative implications for

the following wheat crop (Hobbs and Gupta, 2003; Timsina and

Connor, 2001). The repeated transitions from anaerobic (during

the rice crop) to aerobic (during the wheat crop) soil conditions,

and vice versa, also affect soil nutrient relations and the

chemical and biological environment of the soil. Possibly

because of a combination of these effects, yield stagnation or

even decline, has become a major concern for the RW system

(Ladha et al., 2003). Moreover, overpumping of the shallow

groundwater aquifers is leading to declining water availability

for irrigation (Singh, 2000). Compared with other grain crops,

lowland rice requires more water at the field level because of the

relatively large water requirements for wet land preparation, the

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B.U. Choudhury et al. / Field Crops Research 100 (2007) 229–239230

continuous seepage and percolation flows induced by the

ponding of water, and the relatively high evaporation rates from

the ponded water surface (Bouman and Tuong, 2001; Tuong

et al., 2005). Therefore, efforts to reduce the water use in the

RW system focus on the rice crop.

Since the 1970s, researchers in India have been experiment-

ing with intermittent irrigation (also called alternate wetting

and drying) in single cropping of rice, and succeeded in

reducing water with various degrees of yield penalty (see

Bouman and Tuong, 2001, for overview). One of the recently

proposed innovations to improve the productivity of the whole

RW system and reduce water requirements is the use of

permanent raised beds, inspired by the success of the system in

high-yielding, irrigated wheat–maize areas in Mexico (Sayre

and Hobbs, 2004). Among the suggested benefits are improved

water and nutrient use efficiency, improved water management,

higher yields, and – when the operations are mechanized –

reduced labor requirements and improved seeding and weeding

practices (Connor et al., 2003; Hobbs and Gupta, 2003).

Balasubramanian et al. (2003) and Hobbs and Gupta (2003)

reported initial results of on-station trials and farmer-

participatory evaluation of rice on beds in various states in

the RW belt in India. Yield of rice transplanted or direct-seeded

on beds was plus/minus 5–6% of that of puddled transplanted

rice, while irrigation water savings averaged about 37–40%.

Kukal et al. (2005), however, reported yield reductions of up to

50% and more of rice grown on raised beds compared with

puddled transplanted rice. In most of these reports, the

hydrological conditions of the trials were not recorded, and it is

not known whether the puddled transplanted fields were

continuously flooded or had a system of intermittent irrigation.

This is an important consideration in assessing whether the

raised beds saved irrigation water because of their particular

geometry, or whether the water savings were the result of

applied intermittent irrigation which can also be applied to

direct-seeded crops on flat land (Cabangon et al., 2002; Tabbal

et al., 2002; Kukal et al., 2005). It is also not known whether the

savings in irrigation water were caused by reduced seepage and

percolation or by reduced evapotranspiration. This is important

since water lost by seepage and percolation returns to the

(shallow) groundwater and is potentially available for reuse.

Hence, savings in seepage and percolation from individual

fields may not be real savings at a larger spatial scale (Seckler,

1996) and will not mitigate the fall of groundwater tables.

Finally, very little is known on the impacts of raised beds on the

whole rice–wheat rotation. It is suggested that foregoing wet

land preparation and puddling in rice will improve soil

conditions for the subsequent wheat crop (Connor et al., 2003;

Table 1

Soil properties of the experimental fields at 0–20 cm depth, except for saturated c

Year Texture (%) Bulk density

(g cm�3)

Water content

Sand Silt Clay Saturation

2001–2002 52 34 14 1.64 45

2002–2003 32 41 27 1.53 49

Hobbs and Gupta, 2003), but little evidence exists so far

(Humphreys et al., 2005; Kukal et al., 2005).

This paper reports on rice–wheat experiments that aim to

investigate the benefits of permanent raised beds in terms of

yield, water use and water productivity of both the rice and the

subsequent wheat crop. We attempt to attribute any water

savings with raised beds to the system itself or to the

particular water management that could also be implemented

with flat lay-outs. We quantify the soil water balance

components to determine the source of the water savings,

i.e., whether they arise from reduced percolation or from

reduced evapotranspiration. Finally, we present suggestions

for further research to take the development of raised bed

systems further.

2. Material and method

2.1. Site description

Two rice–wheat experiments were conducted in 2001–2003

at the research farm of the Indian Agricultural Research

Institute, New Delhi, India, at an elevation of 228 m (288360Nand 778120E). The climate of the area is semi-arid with an

average annual temperature of 25 8C and average annual

rainfall of 650 mm. The experiment in 2002–2003 was at a

different location on the farm than the experiment in 2001–

2002 because of problems with access to irrigation water

experienced in 2001–2002. In 2001–2002, the soil was a sandy

loam and in 2002–2003 it was a loam. At both sites, the soil was

classified as Typic Haplustept, with rather low nitrogen (N)

contents and medium phosphorus (P) and potassium (K)

contents (Table 1). The groundwater table was more than 4 m

below the soil surface throughout the year.

2.2. Experiment design

The two experiments were exactly the same in design and

implementation in both years. They were laid out in a

randomized block design with four replicates and plot sizes of

10 m � 7 m. Rice was grown in summer and wheat in winter-

spring (Table 2). For rice, cultivar Pusa-44 was grown in six

treatments: transplanted (TPR), wet-seeded (WSR), dry-seeded

on raised beds (RB) with two water management scenarios (see

below), dry-seeded on ‘‘flat beds’’ (FB) and dry-seeded on flat

land (DSR). The transplanted and wet-seeded treatments were

continuously flooded whereas the other treatments had aerobic,

nonflooded soil conditions and are henceforth referred to as

‘‘aerobic treatments’’. The flooded transplanted and wet-seeded

onductivity which is at 0–60 cm depth

(wt.%) Saturated

conductivity (cm h�1)

Available nutrients

(kg ha�1)

pF 2 pF 4.2 N P K

22 6 0.59 215 15 339

29 11 0.51 186 23 341

B.U. Choudhury et al. / Field Crops Research 100 (2007) 229–239 231

Table 2

Cropping calendar for rice and wheat in 2001–2003

Year Treatmenta Sowing Transplanting Panicle initiation Flowering Harvest

Rice

2001 TPR 1 July 21 July 20 August 19 September 7 November

WSR 5 July – 29 August 27 September 8 November

DSR, FB, RB 5 July – 20–23 September 20–23 October 25–28 November

2002 TPR 29 June 19 July 23 August 21 September 10 November

WSR 29 June – 4 September 30 September 11 November

DSR, FB, RB 29 June – 5–28 September 21–24 October 4–7 December

Wheat

2001–2002 TPR, WSR, DSR, FB, RB 15 December – – 15 March 21 April

2002–2003 TPR, WSR, DSR, FB, RB 28 December – – 21 March 2 May

a Treatment abbreviations are explained in the text.

treatments represent conventional farmers’ practices, whereas

the aerobic treatments are water-saving practices. In the

transplanted and wet-seeded treatments, the soil was puddled

by plowing and frequent harrowing using a four-wheel power

tiller under flooded conditions. In the transplanted treatment, 3

weeks old seedlings were transplanted in hills spaced

15 cm � 20 cm apart. In the wet-seeded treatment, pre-

germinated seeds were manually sown in rows 20 cm apart

at a rate of 60 kg ha�1. The raised beds were freshly prepared

(both years) mechanically by a bed planter cum seed drill, and

were 37 cm wide, separated by furrows that were designed to be

30 cm wide and 22.5 cm deep. However, during the growing

season the beds slumped so that the furrows were only 5–10 cm

deep by the end of the growing season. Dry rice seeds were

sown by the same machine, at a rate of 60 kg ha�1 in two rows

spaced 20 cm apart on the beds, leaving a space of 47 cm

between the rows across the furrows. To separate the effect of

water management from that of the raised beds themselves, the

same row spacing was used on flat land in the ‘‘flat-bed’’

treatment (FB). Compared with the wet-seeded treatment, the

raised bed and flat-bed configurations had the same seed density

per square meter but about 30% less rows because of the 47 cm

‘‘gap’’. In successful raised bed systems, plants make up for this

loss in covered area by increased leaf growth and production at

the edges of the beds (Hobbs and Gupta, 2003; Kukal et al.,

2005). To test this phenomenon, the dry-seeded treatment

(DSR) consisted of dry-seeded rice on flat land at the rate of

60 kg ha�1 in rows regularly spaced 20 cm apart similarly to

the row spacing in the wet-seeded treatment. In both the DSR

and the FB treatments, the soil was dry plowed and harrowed

before sowing.

Irrigation water was applied using flexible hoses. To prevent

seepage flows between plots, the flooded plots (TRB and WSR)

were separated by a strip of bare soil of 2 m width from the

aerobic plots. In addition, plastic sheets were installed in the

centre of the bunds down to a depth of 40 cm. The sheets were

installed about 1 month before land preparation and puddling to

minimize damage to the plow pan. In the transplanted and wet-

seeded treatments, standing water of 3–7 cm depth was

maintained from establishment to 1 week before harvest. In

the aerobic treatments, flush irrigation (across the flat land or

through the furrows) was applied about every other day to keep

the root zone close to field capacity throughout the growing

season. In addition, an extra water treatment in the raised beds

(RB20) consisted of the application of irrigation water when the

soil water tension at 20 cm depth rose above 20 kPa (monitored

with installed tensiometers). In all treatments, last irrigations

were applied about 1 week before harvest. Nitrogen was

applied at the rate of 120 kg ha�1, of which 50% was applied

basal (just before sowing or transplanting), 25% at maximum

tillering and 25% at flowering. Other basal fertilizer applica-

tions were 30 kg P ha�1, 60 kg K ha�1, 25 kg ZnSO4 ha�1 and

50 kg FeSO4 ha�1. To control weeds, the pre-emergence

herbicide butachlor was applied at the rate of 0.5 kg active

ingredients per hectare followed by three to four hand weedings

in the standing crop. To control nematodes, carbofuran 3 G was

applied at the rate of 1.5 kg active ingredients per hectare at

land preparation.

After harvest of the rice crop, wheat variety HD-2687 was

sown. For convenience sake, we use the abbreviations of the

rice treatments to indicate the same plots during the wheat crop.

In all flat plots, land was prepared with two passes of the

cultivator followed by one planking. In the formerly

transplanted (TPR), wet-seeded (WSR) and dry-seeded flat

plots (DSR), wheat was sown with a seed drill in rows spaced

20 cm apart. In the formerly flat-bed plots (FB), wheat was

sown with a seed drill in the raised bed configuration, i.e., two

rows spaced 20 cm apart with a space of 47 cm till the next set

of two rows. In the raised bed plots (RB), the beds were

reshaped manually and sown with wheat in two rows of 20 cm

apart on the beds (thus, the same beds as in rice were used). In

all treatments, the seeding rate was 100 kg ha�1. Fertilizers P

and K were applied basally at the rate of 30 and 60 kg ha�1,

respectively. Nitrogen was applied at the rate of 120 kg ha�1, of

which 50% was applied basal, 25% at crown root initiation and

25% at flowering. Four irrigations of 6–7.5 cm each were given

to all treatments at crown root initiation, tillering, flowering and

the dough stage.

2.3. Measurements

In rice, soil samples were collected for measuring the soil

water content in the root zone (0–30 cm) after land preparation

just before crop transplanting (in TPR) or sowing (all other


treatments) and straight after harvest. Percolation rates were

measured daily by recording the depth of water in plastic

cylinders of 45 cm length (15 cm kept above the soil surface).

The cylinders were kept closed at the top to prevent evaporation

losses. The water level in the cylinders was kept at the same level

as the surrounding water depth in the plots by frequent refilling.

In the raised beds, the cylinders were installed in the furrows. In

the raised beds that were irrigated at 20 kPa (RB20), tensiometers

installed at 20 and 40 cm depth in the centre of the beds were

daily monitored. In wheat, soil samples were collected in the 0–

90 cm root zone to determine the soil water content just before

sowing (but after land preparation), straight after harvest and just

before and after each irrigation application. In both rice and

wheat, the amount of applied irrigation water was measured with

a flow meter installed in the flexible hoses.

In 2001, crop samples of rice were taken from 12 hills in the

transplanted treatment, and from two row sections of 50 cm

each in all direct-seeded treatments, at mid tillering, panicle

initiation, flowering, half-way grain filling, and harvest. In

2002, an additional sample was taken at transplanting (only in

TPR) or at 20 days after sowing (all other treatments). For all

samples, dry biomass was determined after drying in the oven

for 3–5 days at 60 8C until a constant weight was reached.

Green leaf surface area to determine leaf area index (LAI) was

measured with an automatic leaf area meter for all samples

except the one taken at harvest. For wheat, two row sections of

50 cm each were collected at tillering, jointing, flowering and

harvest for biomass determination in the same way as for rice.

Samples for the determination of LAI were collected at crown

root initiation, tillering, jointing, flowering and the dough-ripe

stage. At maturity, an area of 6 m2 area was harvested for both

crops in both years to determine yield and yield components.

The grain yield was expressed at 14% moisture content.

Daily weather data were obtained from the meteorological

station at the experiment site.

2.4. Analyses and calculations

The water balance of the root zone of a cropped field is:

I þ R ¼ ETþ Pþ Sþ Roff þ dW ðmmÞ (1)

where I is the irrigation, R the rainfall, ET the evapotranspira-

tion, P the percolation below the root zone, S the seepage, Roff

the runoff and dW is the change in soil water storage in the root

zone.

In rice, I and R were directly measured. Roff was 0 because

the plots were bunded (30 cm height) and no bund overflow

occurred. S was assumed to be 0 because of the installed plastic

sheets and because the light-textured soil favored vertical rather

than horizontal water movement. The water flow measured in

our percolation tubes served as proxy for the percolation P of

water from the bottom of the 0–30 cm root zone. For the

nonflooded plots, the percolation rate measured in the cylinders

may be larger than that from the whole plot since water may

stand longer after irrigation in the cylinders than in the whole

plot (no root water uptake and no evaporation). Also, cylinders

do not capture the spatial variability that is present in the plots

and the estimated values for P may be less accurate than the

other components of the water balance. The total change in

stored water, dW, was calculated from the difference in

measured soil water contents just before crop establishment

(but after land preparation) and straight after harvest. ET was

calculated as the residual of Eq. (1), and thus includes all

measurement errors in the other water balance terms.

In wheat, I and R were directly measured and, like in rice,

Roff and S were 0. ET was calculated from the change in

measured soil water content before and after each irrigation,

taking account of the rainfall during those periods. On the days

of irrigation, ET was estimated to be 80% of measured pan

evaporation. The dW was calculated from the difference in

measured soil water contents just before sowing and straight

after harvest. The deep percolation beyond 90 cm depth, P, was

calculated as the residual of Eq. (1), and thus includes all

measurement errors in the other water balance terms.

For both rice and wheat, we calculated two measures of crop

water productivity (g grain kg�1 water):

WPET: weight of grains over cumulative weight of water

evapotranspired.

WPIR: weight of grains over cumulative weight of water

inputs by irrigation and rain during crop growth.

For rice, we also calculated:

WPIRT: weight of grains over cumulative weight of water

inputs by irrigation and rain during crop growth and land

preparation.

Data were analyzed following analysis of variance and

means of treatments were compared based on the least

significant difference test (LSD) at the 0.05 probability level.

3. Results

3.1. Crop development and soil water tension

For rice under flooded transplanted (TPR) or flooded wet-

seeded (WSR) conditions, the growth duration from sowing to

harvest was 129 days in 2001 and 134 days in 2002 (Table 2).

The crops in the aerobic treatments (DSR, FB and RB) lasted 17

days longer in 2001 and 27 days in 2002, with no difference in

duration among the treatments. The duration of winter wheat

was 127 days in 2001–2002 and 125 days in 2002–2003 in all

treatments.

In rice, the biomass in the two flooded treatments (TPR and

WSR) developed faster and reached higher end values than in

the raised beds (RB and RB20) and flat bed (FB) (Fig. 1A). The

biomass in the dry-seeded treatment with 20 cm row spacing

(DSR) developed the same as in the raised beds and the flat beds

during early growth, but caught up with the flooded treatments

in the second half of the growing season. In raised beds, the

biomass with irrigation at 20 kPa developed slower than with

irrigation around field capacity, though the difference was not


Fig. 1. Biomass (A) and leaf area index (LAI) (B) of rice in time in 2001 (top panels) and 2002 (bottom panels). Symbols are treatment means and the bars (hardly

visible) are the standard errors. The average standard errors over the growing season were 1.1–1.8% of the means for biomass and 1.4–3.2% of the means for LAI.

Treatment abbreviations are explained in the text.

very large. The trends in LAI among the treatments followed

those in biomass (Fig. 1B).

In wheat, the biomass in the three treatments with 20 cm row

spacing was about the same (independent of soil tillage in the

preceding rice crop) and developed faster than the biomass in

the three raised bed and flat-bed treatments (Fig. 2A). In 2003,

the biomass in the flat beds was noticeable lower than in the

raised beds. Like in rice, the trends in LAI among the treatments

followed those in biomass: the three crops on raised and flat

beds had mutually comparable values that were consistently

lower than the three crops with 20 cm row spacing (Fig. 2B).

The soil water tension in rice in the RB20 raised beds is

shown in Fig. 3. With the threshold for irrigation at 20 kPa, the

soil water tension fluctuated mostly between 3 and 25 kPa at

20 cm depth and between 5 and 15 kPa at 40 cm depth. The

average soil water tension over the growing season was close to

field capacity: 11–12 kPa at 20 cm depth and 8–10 kPa at 40 cm

depth. Since the frequency and total amount of irrigation was

higher in all the other aerobic treatments than in the RB20

treatment (Table 3), we can safely assume that those treatments

were indeed kept close to field capacity at 20–40 cm depth

throughout the growing season.

3.2. Water balance

Even between transplanting and harvest, flooded trans-

planted rice received much more water than all other treatments

from sowing till harvest (Table 3). Flooded wet-seeded rice

received 250 mm less irrigation water than transplanted rice in

2001 and 140 mm less in 2002. However, it did receive 90 mm

more rainfall than transplanted rice in 2001 in the period that

transplanted rice was still growing in the seedbed. The three

aerobic treatments at field capacity received 675–793 mm less

irrigation water than flooded transplanted rice in 2001 and 500–

586 mm less in 2002. In 2002, all three aerobic treatments at

field capacity received statistically similar amounts of irrigation

water, while in 2001, the raised beds received some 100–

120 mm less (significantly different) than the flat-bed and the

dry-seeded treatment with 20 cm row spacing. The raised beds

with irrigation at 20 kPa received 70 mm less irrigation water

than the raised beds kept at field capacity in both 2001 and 2002

(both significantly different).

Smaller amounts of irrigation water received were reflected

in both smaller amounts of evapotranspiration and of

percolation losses. Compared with flooded transplanted rice,

the evapotranspiration of flooded wet-seeded rice was 70–

90 mm lower. In the wet-seeded treatment, the soil was left

without ponded water for 1 week after sowing (to avoid floating

of the seeds), which may have contributed to this lower

evapotranspiration. The evapotranspiration of dry-seeded rice

with 20 cm row spacing was 225–339 mm lower than that of

flooded transplanted rice, and that of both flat and raised beds at

field capacity was 290–410 mm lower than that of flooded

transplanted rice. The relatively low evapotranspiration from


Fig. 2. Biomass (A) and leaf area index (LAI) (B) of wheat in time in 2001–2002 (top panels) and 2002–2003 (bottom panels). Symbols are treatment means and the

bars (hardly visible) are the standard errors. The average standard errors over the growing season were 0.7–1.5% of the means for biomass and 1.4–5.5% of the means

for LAI. Treatment abbreviations are explained in the text.

Fig. 3. Soil water tension at 20 and 40 cm depth in rice on raised beds that are

irrigated at 20 kPa threshold level at 20 cm depth (RB20 treatment) in 2001 (top

panel) and 2002 (bottom panel). Symbols are treatment means. The average

standard error over the growing season was 5% of the mean in 2001 and 3.9% of

the mean in 2002.

dry-seeded rice and flat and raised beds, is explained by lower

values of LAI in the vegetative growing season (Fig. 1B), thus

reducing transpiration, and less evaporation from the dry soil

surfaces compared with that from standing water in both

flooded treatments. The evapotranspiration of raised beds that

were irrigated at 20 kPa was only 9–30 mm lower than that of

raised beds kept at field capacity. The evapotranspiration of the

raised beds and the flat beds was statistically the same in both

years. The percolation of flooded wet-seeded rice was 50–

70 mm smaller than that of transplanted rice, and that of the

three aerobic treatments kept at field capacity was 160–400 mm

smaller (all three statistically the same each year except for flat

beds in 2001). The percolation of raised beds that were irrigated

at 20 kPa was a significant 70–90 mm lower than that of raised

beds kept at field capacity. The soil water content in the two

flooded treatments was close to saturation at the start and end of

the experiment, and there was no change in soil water content.

The three aerobic treatments kept at field capacity stored some

extra 18–26 mm water in the soil after harvest, while the raised

beds irrigated at 20 kPa stored 39–48 mm.

All wheat treatments on flat land received about the same

amount of irrigation water, independent of row spacing. The

raised beds used significantly less water than the other

treatments, although the absolute differences were relatively

low in the order of 30–35 mm only. The flat beds and the raised

beds had significantly less evapotranspiration than the other

treatments, though again, absolute differences were relatively


Table 3

Components of the seasonal water balance (mm) of rice and wheat in 2001–2002 and 2002–2003

Treatmenta Rice Wheat

Ib Rc ETd Pe dWf Ib Rc ETd Pe dWf

2001–2002

TPR 1360 a 249 781 a 828 a 0 a 285 ab 25 307 a 57 bc �54 a

WSR 1108 b 358 710 b 756 b 0 a 286 ab 25 304 a 61 b �54 a

DSR 685 c 361 556 c 466 d 24 a 298 a 25 312 a 53 c �42 b

FB 669 c 361 494 d 510 c 26 a 282 b 25 275 b 78 a �46 b

RB 567 d 361 475 d 433 d 20 a 256 c 25 274 b 59 b �53 a

RB20 497 e 361 466 d 344 e 48 b 252 c 25 279 b 44 d �46 b

2002–2003

TPR 1313 a 265 899 a 679 a 0 a 264 a 95 351 a 55 b �47 a

WSR 1171 b 265 806 b 630 a 0 a 253 a 95 349 a 46 c �48 a

DSR 813 c 265 560 c 493 b 25 a 260 a 95 344 a 48 c �37 c

FB 764 c 265 489 d 517 b 23 a 252 a 95 324 b 65 a �42 b

RB 727 c 265 477 d 497 b 18 a 228 b 95 320 b 49 c �46 a

RB20 648 d 265 447 d 427 c 39 a 226 b 95 316 b 45 c �40 b

Data are accumulated values from sowing till harvest except for transplanted rice that are from transplanting to harvest (thus excluding any irrigations for land

preparation before sowing or before transplanting). Means in a column followed by common letters (a–e) are not significantly different at the 5% level.a Treatment abbreviations are explained in the text.b I, irrigation.c R, rain.d ET, evapotranspiration.e P, deep percolation beyond root zone.f dW, change in soil water stored in root zone (negative values mean net extraction and positive values mean net addition).

small with maximum values of about 36 mm only. Unlike in

rice, there was an extraction of stored soil water in the 0–90 cm

zone of 45–78 mm, with small but significant differences

among the treatments. Percolation losses beyond 90 cm depth

were 37–53 mm only, again with small but significant

differences among the treatments.

Table 4

Yield (kg ha�1 and water productivity WP (g grain kg�1 water) of rice and wheat

Treatmenta Rice

Yield WPETb WPIR

c

2001–2002

TPR 5500 a 0.70 ab 0.34 b

WSR 4000 b 0.56 c 0.27 c

DSR 4200 b 0.76 a 0.40 a

FB 3219 c 0.65 b 0.31 bc

RB 3214 c 0.68 b 0.35 b

RB20 3106 c 0.67 b 0.36 ab

2002–2003

TPR 5440 a 0.60 b 0.34 ab

WSR 4792 b 0.59 b 0.33 b

DSR 4204 bc 0.75 a 0.39 a

FB 3720 c 0.76 a 0.36 ab

RB 3720 c 0.78 a 0.38 ab

RB20 3011 d 0.67 b 0.33 b

Means in a column followed by common letters (a–d) are not significantly differea Treatment abbreviations are explained in the text.b WPET, water productivity based on evapotranspiration during the growing seasc WPIR, water productivity based on irrigation plus rainfall during the growing sd WPIRT, water productivity based on irrigation and rainfall during the growing

3.3. Yield

In rice, highest yields of around 5.5 t ha�1 were obtained in

the flooded transplanted treatment (Table 4). The flooded wet-

seeded treatment yielded a significant 1.5 t ha�1 less in 2001

and 0.6 t ha�1 less in 2002. The flat beds and the raised beds

in 2001–2002 and 2002–2003

Wheat

WPIRTd Yield WPET

b WPIRc

0.28 cd 4853 a 1.58 a 1.57 a

0.23 d 4459 b 1.47 bc 1.43 b

0.40 a 4927 a 1.58 a 1.52 a

0.31 bc 3829 c 1.39 c 1.25 c

0.35 b 4157 b 1.51 ab 1.48 ab

0.36 ab 3826 c 1.37 C 1.39 ab

0.28 b 3828 b 1.09 b 1.07 b

0.27 b 3911 ab 1.12 ab 1.13 a

0.39 a 3997 a 1.16 a 1.13 a

0.36 a 2880 d 0.89 d 0.83 d

0.38 a 3247 c 1.02 c 1.01 c

0.33 ab 3199 c 1.01 c 0.99 c

nt at the 5% level.

on.

eason.

season plus water used during wet land preparation (for rice only).


kept at field capacity had statistically comparable yields that

were 2.3 t ha�1 lower in 2001 and 1.7 t ha�1 lower in 2002 than

flooded transplanted rice those years. The dry-seeded rice with

20 cm row spacing yielded 1 t ha�1 more than the flat beds and

raised beds in 2001 (significantly different), and 0.5 t ha�1

more than the flat beds and raised beds in 2002 (not

significantly different). The raised beds that were irrigated at

20 kPa had the same yield as the beds kept at field capacity in

2001, but a significant 0.7 t ha�1 lower yield in 2002.

The differences in yield of wheat (Table 4) were significant

among most treatments, though small in absolute value

compared with the differences in yield of rice. In both years,

highest and mostly statistically comparable yields were

obtained in the 20 cm row spacing treatments following the

transplanted, the wet-seeded or the dry-seeded 20 cm row

spacing rice treatments. The flat beds and the raised beds had

significantly lower yields in both years, i.e., 0.8–1.0 t ha�1

lower than the highest yield in 2001–2002 and 0.7–1.1 t ha�1

lower than the highest yield in 2002–2003.

3.4. Water productivity

In rice, differences in water productivity among treatments

were relatively small and not consistent between the 2 years

(Table 4). In general, the lower yields in the aerobic dry-seeded

treatments were compensated for by lower water inputs, so that

water productivity did not vary much. In 2001, water

productivity with respect to evapotranspiration (WPET) was

highest in the dry-seeded 20 cm row spacing and the

transplanted treatments, lowest in the wet-seeded treatment

and intermediate in the flat beds and the raised beds

(statistically the same). In 2002, however, WPET was highest

in the three dry-seeded treatments kept around field capacity

(all three statistically the same), intermediate in the raised beds

irrigated at 20 kPa, and lowest in the two flooded treatments

Table 5

Yield components of rice and wheat in 2001–2002 and 2002–2003

Treatmenta Rice

Panicles (m�2) Spikelets

per panicle

Fertile spikelet (%)

2001–2002

TPR 236 b 145 a 83 a

WSR 238 b 135 b 76 b

DSR 296 a 120 c 74 bc

FB 205 d 124 c 76 b

RB 220 c 123 c 71 c

RB20 205 d 112 d 68 d

2002–2003

TPR 246 b 148 a 82 a

WSR 268 a 131 b 75 c

DSR 288 a 122 c 72 c

FB 219 c 126 c 79 b

RB 235 bc 121 c 74 c

RB20 220 c 111 d 66 d

Means in a column followed by common letters (a–e) are not significantly differea Treatment abbreviations are explained in the text.

(both statistically the same). The water productivity with

respect to combined irrigation and rain water input (WPIR) was

about one-half of that of WPET in all treatments but had the

same trends as of WPET across treatments. The higher values of

WPET than of WPIR are explained by the large water losses by

percolation, which were in the same order of magnitude as the

losses by evapotranspiration in all treatments (Table 3).

In 2001–2002, the WPET of wheat was more than two times

higher than that of rice (Table 4). In 2002–2003, however, with

lower wheat yields than in 2001–2002, the WPET of wheat was

only 1.2–1.9 times higher than that of rice. The higher WPET

values of wheat can be explained by the lower evaporative

demand from the atmosphere in winter and early spring (caused

by lower temperatures and less solar radiation) when wheat was

grown than in summer when rice was grown (Zwart and

Bastiaanssen, 2004). Like in rice, the differences in WPET

among the treatments were small, though the flat beds and the

raised beds consistently had the lowest values. Unlike in rice,

the WPIR was comparable to the WPET because nearly all

evapotranspiration was met by irrigation and rainfall, and losses

by deep percolation were small.

3.5. Yield components

There were very few consistent trends in yield components

among treatments (Table 5). In both rice and wheat, the number

of panicles per square meter was consistently lowest in the flat

beds and the raised beds, and no compensation of extra tillering

at the edges of the beds was observed to compensate for the loss

of filled space. In wheat, the low number of spikes per square

meter in the flat beds and the raised beds was compensated for

by the highest number of grains per spike of all treatments, but

no such compensation was found in rice. Flooded transplanted

rice consistently had highest values for number of spikelets per

panicle, percentage spikelet fertility and 1000 grain weight of

Wheat

1000 grain

weight (g)

Spikes (m�2) Grains

per spike

1000 grain

weight (g)

22.4 a 396 b 37 b 35.8 ab

19.2 e 380 b 35 b 35.3 b

20.3 c 417 a 34 b 37.3 a

20.0 d 219 d 49 a 35.8 ab

20.5 b 248 c 49 a 36.3 ab

19.5 e 230 d 48 a 35.1 b

21.2 a 355 b 37 b 31.0 a

20.3 b 380 a 38 b 28.8 b

19.0 c 369 ab 39 b 29.0 b

19.6 b 208 c 47 a 29.0 b

20.1 b 231 c 49 a 30.0 ab

19.4 c 228 c 48 a 29.0 b

nt at the 5% level.


all treatments in both years. The fact that there were fewer

spikelets per panicle, lower spikelet fertility and lower grain

weight suggest that there were more factors than the wide row

spacing reducing yield on the flat and raised beds.

4. Discussion

4.1. Rice

The yield of rice in our experiment varied between 3.2 (flat

beds and raised beds) and 5.5 (flooded transplanted) t ha�1, and

compares well with yields compiled from other experiments on

water savings in the Indo-Gangetic Plain in India (Bouman and

Tuong, 2001; Kukal et al., 2005; Timsina and Connor, 2001).

The yield of dry-seeded rice on raised beds was 32–42% lower

than that of flooded transplanted rice and 20–22% lower than

that of flooded wet-seeded rice. Most of the yield difference was

caused by the difference in row spacing and not so much by the

difference in water regime. Dry-seeded rice that was kept

around field capacity had 5% higher to 12% lower yield than

wet-seeded flooded rice with the same seed rate and row

spacing (20 cm), so more or less comparable yields on average.

But when the row spacing as adopted on beds was used (20–

47 cm), yields of dry-seeded rice dropped 12–23% compared

with the continuous row spacing of 20 cm. There was no

difference at all between the yields of dry-seeded rice with the

20–47 cm row spacing laid out on flat land or on raised beds,

and in none of the two lay-outs did the rice crop compensate for

the loss of space by increased tillering or increased leaf area

growth at the edges of the rows/beds.

Total water input (irrigation plus rainfall) varied from

930 mm (raised beds) to 1600 mm (flooded transplanted). Total

water input in rice on raised beds was 38–42% less than in

flooded transplanted rice and 32–37% less than in flooded wet-

seeded rice. For comparison, Humphreys et al. (2005) reported

reductions in irrigation water use of 12–60% in transplanted or

dry-seeded rice on raised beds compared with flooded

transplanted rice from an analysis of several farmer and

researcher trials conducted in the Indo-Gangetic Plain. The

reduced water use in our experiment was mainly caused by the

difference in water management between these treatments and

not by the geometry of the raised beds per se. In 2002, water use

was statistically the same in all fields that were kept around field

capacity, independent of row spacing or whether the crop was

established on beds or on flat land. In 2001, water use in raised

beds was 100 and 120 mm less than in dry-seeded rice on flat

land kept at the same soil water content with 20–47 and 20 cm

row spacing, respectively. Although this difference was

significant, it was small compared with the difference of

538 mm total water input between flooded wet-seeded rice and

rice on raised beds kept around field capacity. Allowing the soil

in raised beds to dry out a little bit more (from around field

capacity to 20 kPa tension at 20 cm depth) reduced irrigation

water inputs with an additional 70 mm but resulted in an extra

yield loss of 0.1–0.7 t ha�1.

The lower water inputs in dry-seeded rice kept at field

capacity (either on flat land or on raised beds) than in flooded

rice was caused by both reduced rates of evapotranspiration

and reduced rates of percolation. Dry-seeded rice at field

capacity on flat land had 22–31% less evapotranspiration and

22–38% less percolation than flooded wet-seeded rice with the

same (20 cm) row spacing. Dry-seeded rice at field capacity on

raised beds, or on flat land with 20–47 cm row spacing, had 30–

41% less evapotranspiration and 18–43% less percolation than

flooded wet-seeded rice with 20 cm row spacing. Experiment-

ing with raised beds and dry-seeded rice on a silty loam (19%

clay, 26% silt and 55% sand) at Modipuram (at 298010N and

778450E close to our experimental site), Sharma et al. (2002)

reported quite similar results for reductions in water flows.

Compared with flooded transplanted rice, with a total water

input of 4240 mm, dry-seeded rice kept at field capacity on flat

land or on raised beds in the same geometry as in our field

experiment, had 25% less evapotranspiration and 51–59% less

seepage and percolation. Since Sharma et al. did not use plastic

sheets in the bunds, they had additional water loss from flooded

plots by seepage, and keeping plots around field capacity

reduced these seepage losses compared with their flooded

plots.

Reduced rates of percolation may mean real water savings at

the field level, but, when percolating water returns to the

groundwater and does not deteriorate in quality, cannot be

considered real water savings at a higher spatial scale. The

reduced evapotranspiration rates, on the other hand, are real

water savings since these losses cannot be recaptured and

reused anymore. However, the reduced evapotranspiration rates

come at a cost of severe yield loss. Mostly, the gains in water

savings in dry-seeded rice kept around field capacity compared

with flooded rice were offset by yield reductions, and water

productivities, either in terms of evapotranspiration (WPET) or

of total water input (WPIR), varied little among the treatments.

The WPET in our experiments varied between 0.56 and 0.78 g

grains kg�1 water among treatments, and are at the low side of

the range of 0.6–1.6 g grains kg�1 water compiled by Zwart and

Bastiaanssen (2004) for rice. The low WPET values in our

experiments are probably caused by relatively low yields since

the data base by Zwart and Bastiaanssen contains yields going

up to 10 t ha�1. The WPIR varied between 0.27 and 0.40 g

grains kg�1 water during crop growth (going down to 0.23

when wet land preparation was taken into account in the

puddled treatments). Although these values are at the low end of

the range of 0.2–1.2 g grains kg�1 water compiled for rice by

Bouman and Tuong (2001), these values are typical for the rice–

wheat area in the Indo-Gangetic Plain (Humphreys et al., 2005;

Kukal et al., 2005).

4.2. Wheat

The yield of wheat in our experiment varied between

2.9 t ha�1 (flat beds, 20–47 cm row spacing) and 4.5 t ha�1 (flat

land, 20 cm row spacing), and compares well with yields

compiled from other field experiments in the Indo-Gangetic

Plain in India (Kukal et al., 2005; Timsina and Connor, 2001).

Our wheat was sown relatively late in the season (Table 2), and

some researchers have suggested that three rows on the beds


would be needed in late-sown wheat to get high(er) yields

(Kukal et al., 2005). In terms of response to crop establishment,

slightly different results were obtained in wheat than in rice.

Highest yields were obtained with 20 cm row spacing on flat

land. Yields on flat land were 19–26% lower when the 20–

47 cm row spacing was used. However, with 20–47 cm row

spacing on raised beds, yields only dropped 12–17% from the

yields with 20 cm row spacing on flat land, and yields were

significantly higher on raised beds than on flat land with the

same row spacing. Although the wheat crop on the raised beds

had the highest number of grains per spike, the number of

spikes per square meter was still too low compared with the

20 cm row spacing on flat land to fully compensate for the loss

in space. Similar results were reported by Sharma et al. (2002)

for wheat following rice in their Modipuram experiment (see

above), where wheat yield on raised beds was 18% lower than

with 20 cm row spacing on flat land. In our experiment, there

was no negative carry-over effect of the puddling and

compaction of the soil in the transplanted and wet-seeded rice

treatments on yield of the subsequent wheat crop in none of the

2 years. However, our experiments were newly established in

both years and carry-over effects may only occur in long-term

continuous cropping of rice–wheat (Timsina and Connor,

2001).

4.3. Conclusion and further research issues

The raised bed technology for rice–wheat is still in its

infancy of development and it is too soon to draw firm

conclusions on the potential of the system. Humphreys et al.

(2005) and Kukal et al. (2005) concluded from analyzing

various early reports on the raised bed system in the Indo-

Gangetic Plain that with transplanting on beds, rice yields were

‘‘similar or lower compared with puddled flooded transplanted

rice’’ and with dry seeding on beds ‘‘usually lower’’. However,

in our study using dry seeding on beds, rice yields were much

lower than from flooded transplanted and wet-seeded rice, and

even wheat yields were lower on beds than on flat land.

Reductions in water inputs in rice were substantial but could

also be accomplished with dry seeding on flat land with the

same water management (i.e., keeping the root zone around

field capacity). Reduced water inputs and yield reductions

balanced each other so that rice water productivity was

comparable among flooded, dry-seeded on flat land and dry-

seeded on raised bed treatments. Care must be taken in

extrapolating these experimental results obtained from rela-

tively small plots of 70 m2 to farmers’ fields that may be in the

order of hundreds to thousands of square meters. For example,

the water balance of large fields may deviate from smaller fields

because of smaller bund-to-surface area ratios (resulting in

relatively less underbund seepage) and longer irrigation times

(resulting in more percolation losses, less even distribution of

water, and, hence, maybe more heterogeneity in crop growth).

The differences in field size may also affect relative differences

among the water management treatments. Finally, farmers do

not install plastic sheets in their bunds to prevent seepage and

underbund flows of water.

Several reasons may have caused the relatively low yields in

our aerobic treatments. Despite basal iron and zinc applications,

the young rice plants showed visual symptoms of deficiency in

these elements. In the first year of our experiment, the DTPA-

extractable iron in the root zone of the aerobic plots was 2.15–

2.61 ppm, which was one-half of that in the flooded treatments

(Singh et al., 2002). Moreover, in our experiment, we observed

galls of the root-knot nematodes Meloidogyne graminicola and

Meloidogyne triticoryzae on the roots of rice (Singh et al., 2002).

The root-knot index was statistically the same among the aerobic

treatments and the flooded wet-seeded treatment, but was higher

than in the flooded transplanted treatment. Both micro-nutrient

deficiencies and/or nematodes may have suppressed our yields

under aerobic soil conditions. The occurrence of these problems

has also been reported for nonflooded rice by Ventura and

Watanabe (1978) and George et al. (2002) and requires more

research for the successful development of aerobic rice systems

on raised beds or on flat land (Peng et al., 2006). The rice and

wheat varieties used in our experiment did not compensate for the

loss of space between the beds by increased tillering or increased

leaf area expansion. Hobbs and Gupta (2003) pointed out the

importance of selecting varieties with good spreading ability to

get high yields on raised beds. Atlin et al. (2006) and Bouman

et al. (2006) also demonstrated the importance of selecting or

breeding proper rice varieties for aerobic soil conditions,

combining drought tolerance with high yield capability. Many

weeds emerged in the aerobic plots in our experiments. Although

they were well controlled by manual weeding, the weed problem

is expected to be a constraint to adoption by farmers and requires

the development of proper control mechanisms. Finally, the

instability of the beds as found in our experiment should be

further researched and improved upon. The slumping of beds led

to furrow depths of only 5–10 cm around harvest time, a

phenomenon also observed by the authors in many fields of

farmers experimentingwith rice on raised beds in the Modipuram

area (near New Delhi; unpublished observations).

Acknowledgments

The research reported here was partly supported by the Swiss

Agency for Development and Cooperation (SDC) through the

Water Workgroup of the Irrigated Rice Research Consortium

(IRRC), and by the Dutch Government through the project

‘‘Potentials of water-saving technologies in rice production: an

inventory and synthesis of options’’ of the Comprehensive

Assessment of Water Management in Agriculture.

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Yield and water productivity of rice–wheat on raised beds at New Delhi, India

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