Field Crops Research 158 (2014) 24–33

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Field Crops Research

jou rn al hom ep age: www.elsev ier .com/ locate / fc r

Conservation agriculture in an irrigated cotton–wheat system of thewestern Indo-Gangetic Plains: Crop and water productivity andeconomic profitability

T.K. Dasa, Ranjan Bhattacharyyaa,∗, S. Sudhishri a, A.R. Sharmab, Y.S. Saharawata,K.K. Bandyopadhyaya, Seema Sepata, R.S. Banaa, Pramila Aggarwala, R.K. Sharmaa,A. Bhatiaa, Geeta Singha, S.P. Dattaa, A. Kara, Billu Singha, Parmendra Singha, H. Pathaka,A.K. Vyasa, M.L. Jat c

a Indian Agricultural Research Institute, New Delhi 110 012, Indiab Directorate of Weed Science Research, Jabalpur, M.P., Indiac International Maize and Wheat Improvement Centre (CIMMYT), New Delhi 110 012, India

a r t i c l e i n f o

Article history:Received 14 October 2013Received in revised form17 December 2013Accepted 17 December 2013

Keywords:Broad and narrow bedResidue retentionConventional and zero tillageGross and net returns

a b s t r a c t

Cotton–wheat cropping system is the second most important wheat based system in the South Asia(4.5 M ha) and India (2.6 M ha) and contributes significantly to the food security in the region. However,with the conventional method of crop establishment and crop management, the productivity and profit-ability of the cotton–wheat system is low. Hence, despite non-suitability of growing situations, farmersare inclined towards cultivating the conventionally tilled rice–wheat rotation which has got severe con-sequences on the natural resources as well as the future food security. Therefore, an attempt was madeto develop and evaluate the performances (in terms of system productivity, water productivity and pro-fitability) of conservation agricultural technologies (like permanent narrow and broad-bed planting andresidue management under zero tillage) under an irrigated cotton–wheat system in the region. Treat-ments included farmers’ practice (conventional tillage and flat-bed sowing without residue recycling;CT), and four combinations of raised-bed planting and residue management under zero tillage (viz.,narrow-bed and broad-bed sowing with and without crop residue retention) in the first year. During thesecond year onwards two additional treatments were included: flat-bed sowing under zero tillage withand without residue retention. Results indicate that mean (of last two years) seed cotton yield in theplots under zero tilled permanent broad-bed sowing with residue retention (PBB + R) was about 24 and51% higher compared with zero tilled narrow-bed sowing without residue retention (PNB; 2.91 Mg ha−1)and CT plots (2.59 Mg ha−1), respectively. Similarly, plots under PBB + R had significantly higher mean(of last two years) wheat grain yield than flat-bed zero tilled (ZT) and CT plots. Unlike seed cotton yield,wheat grain yield was not affected by the treatments in the first year. In the second year, plots underPBB + R had about 9 and 11% higher wheat grain yield than PNB (4.37 Mg ha−1) and CT (4.29 Mg ha−1) plots,respectively. Although the system productivity in terms of wheat equivalent yield (WEY) was similar inthe plots under PBB + R and zero tilled-broad permanent bed sowing without residue retention (PBB)and zero tilled narrow-bed sowing with residue retention (PNB + R) in the first year, plots under PBB + Rhad about 15 and 13% higher WEY than PBB and PNB + R plots. Similarly, mean (of the last two years)water productivity of the system in the PBB + R treated plots (12.58 kg wheat grain ha−1 mm−1) was 48,22, 12, 15, 13, 24% higher compared with CT, PNB, PNB + R, PBB, ZT + R and ZT plots, respectively. Theabove-said PBB + R plots also had the highest net returns (based on mean values of last two years) thatwas 36 and 13% higher compared with CT and PNB plots, but was similar to other treatments. Therefore,growing cotton–wheat system under permanent beds with residue retention is recommended underirrigated conditions in this region due to its potential of increased productivity, profitability and resourceconservation.

© 2013 Elsevier B.V. All rights reserved.

∗ Corresponding author. Tel.: +91 7838781447.E-mail addresses: ranjan vpkas@yahoo.com, ranjanvpkas@gmail.com (R. Bhattacharyya).

0378-4290/$ – see front matter © 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.fcr.2013.12.017

T.K. Das et al. / Field Crops Research 158 (2014) 24–33 25

1. Introduction

The sustainability of the rice–wheat system in the Indo-GangeticPlains (IGP) is at risk owing to higher water requirement of therice crop (Hobbs and Gupta, 2004). In addition, the conventionalproduction practices resulted in high cultivation cost and ineffi-cient input use. This calls for identification of suitable croppingsystems other than the rice–wheat under irrigated conditions inthe region. Maize, cotton and pigeonpea are suitable alternativecrops to rice in the kharif (rainy) season in north-western IGPbecause of their relatively low water requirement. Potential pro-ductivity and assured high returns could be realized from thecotton–wheat rotation system (especially after introduction of Btcotton), which also improves the livelihood of the farmers of theregion.

Cotton, an important fibre crop, is grown throughout India underboth rainfed and irrigated conditions on an area of 9.5 millionhectares (M ha) (Mayee et al., 2008). Wheat is grown on 29 M haand meets the nutritional requirement of majority of the peo-ple. Both these crops contribute towards the livelihood of a largenumber of people in India. Development of short-duration early-maturing varieties of cotton and expansion of irrigation facilitieshave led to the cultivation of a cotton–wheat rotation system inthe north-western India. Accordingly, cotton–wheat cropping sys-tem occupies nearly 1.7 M ha in the states of Punjab, Haryana andRajasthan (Monga et al., 2009). However, production of cottonshowed a declining trend in the recent years (Mayee et al., 2008).The major constraints encountered are: inadequate crop stand dueto poor emergence after sowing, seedling burning due to hightemperature at emergence, alkalinity and salinity problems, andincreased incidence of pests, e.g. boll worms, white fly and jassid,and diseases, e.g. wilt, root rot and black cutworm (Brar et al., 1998).Likewise in wheat, delay in sowing under conventional agriculturalpractices due to late cotton harvest caused yield decline because ofprevalence of hot winds during March–April (Pathak et al., 2003).There are many other constraints under traditional/conventionalagricultural practices. Labour unavailability and increasing labourcosts are serious concerns for the timely planting of crops (Jatet al., 2009). In the western Indo-Gangetic Plains (IGP), water isincreasingly becoming scarce because agriculture is facing risingcompetition from the urban and industrial sectors (Toung andBhuiyan, 1994). In many parts of the region, over-exploitationand poor groundwater management has led to decreased watertable and negative environmental impacts (Saharawat et al.,2010). Deterioration of land quality due to different forms ofsoil degradation and excess residue burning are other pervasiveproblems in the region (Bhattacharyya et al., 2013a,b; Das et al.,2013). These factors lead to consideration of conservation agricul-ture (CA) for sustained productivity, profitability and soil quality(Kassam et al., 2011).

Conservation agriculture has the following four principles: (i)minimizing mechanical soil disturbance and seeding directly intountilled soil to improve soil organic matter (SOM) content and soilhealth; (ii) enhancing SOM using cover crops and/or crop residues(mainly residue retention). This protects the soil surface, conserveswater and nutrients, promotes soil biological activity and con-tributes to integrated pest management (IPM); (iii) diversificationof crops in associations, sequences and rotations to enhance sys-tem resilience and (iv) controlled traffic that lessen soil compaction(FAO, 2011). Thus, CA avoids straw burning, improves soil organiccarbon (SOC) content, enhances input use efficiency and has thepotential to reduce greenhouse gas emissions (Bhattacharyya et al.,2012a,b).

The CA technologies involving no- or minimum-tillage withdirect seeding, and bed planting, innovations in residue manage-ment (mainly residue retention) to avoid straw burning and crop

diversification have potential for improving productivity and soilquality, mainly by SOM build-up (Ladha et al., 2009; Bhattacharyyaet al., 2009, 2013a,b). Published results from field experimentsthroughout the globe have shown increased SOC content underzero-tilled soils compared to tilled soils (West and Post, 2002;Alvarez, 2005; Bhattacharyya et al., 2008, 2012a,b). Bed plantinggenerally saves irrigation water (Gathala et al., 2011), labour con-sumption without sacrificing crop productivity (Hobbs and Gupta,2000; Ladha et al., 2009). The permanent bed planting techniquehas been developed for higher production, cost reduction and con-servation of resources (Lichter et al., 2008). Permanent raised bedspermit the maintenance of a permanent soil cover for greater rain-water capture and conservation (Govaerts et al., 2005, 2007). Theadvantages of permanent raised bed planting over conventionalzero tillage (ZT with flat planting) are that it saves irrigation waterand weeding. Fertilization application practices are also easily per-formed by trafficking in the furrow bottoms and the fertilizerscan be banded through the surface residues, reducing potentialnutrient losses (Limon-Ortega et al., 2002) under permanent raisedbed planting. Past research suggests some advantages of broad-beds over narrow-beds in the maize-wheat system. For example,Akbar et al. (2007) reported that there was about 36% water sav-ing for broad-beds and about 10% for narrow-beds compared toflat sowing, and grain yield increased by 6% for wheat and 33%for maize in Pakistan. In both cases, the furrows act as pathwaysfor drainage during excessive rains and conserve rainwater in dryspells (Astatke et al., 2002). Residue retention generally increasesSOC content worldwide (Saharawat et al., 2010) and improves pro-ductivity (Naresh et al., 2012). However, there is a need for widerscale testing of these new technologies under diverse productionsystems, as the CA technologies are site specific and thereforeappraisal of CA is important to have significant adoption (Ladhaet al., 2009).

Jalota et al. (2008) studied the direct and interactive effects ofdate of sowing and tillage-plus-wheat residue management prac-tices on growth and yield of cotton and wheat. They reportedincreased profitability under reduced tillage operations, mainly dueto 50% less sowing cost under reduced tillage. However, cottonyields were 23–39% higher in tillage treatments than minimum-tillage and wheat grain yields in tillage treatments were at parwith reduced tillage (Jalota et al., 2008). Again, water produc-tivity amongst the tillage treatments in cotton was 19–27% lessin minimum tillage than others tillage treatments (Jalota et al.,2008). However, apart from that study, we found no informa-tion on productivity and profitability of the cotton–wheat systemas affected by ZT. Moreover, no information is also available onrelative performance of ZT and zero tilled-broad permanent bedsowing with and without residue retention on the performance ofthe system. Considering these facts, the present study was con-ducted to investigate the impacts of CA technologies (ZT alone,ZT with residue retention and ZT with residue retention and bedplanting) on the performance of a cotton–wheat cropping sys-tem in the western IGP. The objectives were: (i) to evaluate theimpacts of CA on year-wise and mean crop yield and above-ground biomass productivity (net primary productivity) under acotton–wheat system, (ii) to assess the CA effects on water pro-ductivity and net returns during a three-year old study and (iii)to evaluate the performance of narrow versus broad-beds on thecotton–wheat system productivity, water productivity and profit-ability. We hypothesized that (i) ZT with bed planting (both narrowand broad-beds) and residue retention would result in larger cropproductivity, system water productivity and net returns comparedwith farmers’ practice (CT and no residue addition) and (ii) irre-spective of the residue retention, ZT with broad-beds would havehigher system productivity and water productivity than ZT withnarrow-beds.

26 T.K. Das et al. / Field Crops Research 158 (2014) 24–33

Fig. 1. Daily meteorological data of (a) kharif (1/06/12–31/10/12) and (b) rabi sea-sons (1/11/12–31/03/13).

2. Materials and methods

2.1. Site

An experiment on the cotton–wheat cropping system was con-ducted during 2010–2013 at the research farm of the IndianAgricultural Research Institute (IARI), New Delhi, India. Before2010, the plot was under the rice–wheat cropping system (withrecommended mineral fertilization for both crops) for past manyyears. A uniformity trial on wheat was undertaken during Rabi2009–2010 to ensure uniform soil fertility in the entire field.The climate of the research farm is semi-arid with dry hot sum-mer and cold winters. May and June are the hottest monthswith mean daily maximum temperature varying from 40 to46 ◦C, while January is the coldest month with mean daily min-imum temperature ranging from 6 to 8 ◦C. The mean annualrainfall is 710 mm, of which 80% is received during the south-west monsoon from July to September, and the rest is receivedthrough the ‘Western Disturbances’ from December to February.Air remains dry during most part of a year. The mean windvelocity varies from 3.5 km h−1 during October to 4.3 km h−1 inApril. Pan evaporation varied between 3.5 and 13.5 mm d−1 andreference evapo-transpiration from 9 to 15 mm d−1. Daily meanvalues of the parameters during the kharif and rabi seasonsof 2012–2013 recorded at the IARI meteorological observatoryadjoining to the experimental site are presented in Fig. 1(a) and(b).

The soil (0–15 cm layer), taken after the uniformity trial, ofthe experimental site was sandy clay loam in texture, with pH7.7, Walkley-Black C (oxidizable SOC) 5.2 g kg−1, EC 0.64 dS m−1,KMnO4 oxidizable N 182.3 kg ha−1, 0.5 M NaHCO3 extractable P23.3 kg ha−1 and 1 N NH4OAc extractable K 250.5 kg ha−1. The soilcontained sufficient amounts of CaCl2 extractable S and DTPAextractable micronutrients as all of these were above the criticaldeficiency limits.

2.2. Experimental details

The field experiment was conducted with five treatment combi-nations [conventional tillage and flat-bed sowing without residuerecycling (CT), zero tilled permanent narrow-bed sowing withoutresidue retention (PNB), zero tilled permanent narrow-bed sowingwith residue retention (PNB + R), zero tilled permanent broad-bedsowing without residue retention (PBB), zero tilled permanentbroad-bed sowing with residue retention (PBB + R)] arranged ina randomized block design (RBD) with three replications during2010–2011. The treatment details are given in Table 1. In the nextyear onwards, two additional treatments, zero tilled flat bed sowingwithout residue retention (ZT) and zero tilled flat bed sowing with-out residue retention (ZT + R) were employed. Individual plot sizewas 9.0 m × 8.4 m. Conventional tillage (CT) involved one plough-ing each with a cultivator, disc harrow and rotavator, while in ZT,no ploughing was done. Fresh raised-beds were prepared underCT, while in permanent beds, reshaping and planting were donein one go using a raised bed planter. Cotton residue involved theleaves and tender twigs along with boll husks, while wheat residuewas retained as such after harvesting the crop with a combine har-vester that removed wheat residues above ∼30 cm height. It wasobserved that about 20 and 40% of the cotton and wheat residues(stover yields), respectively, were retained in all plots. In the firstyear of the experiment, an estimated quantity of wheat residue(∼2.6 Mg ha−1) was retained for PNB + R and PBB + R plots. Simi-larly, in the second year, the entire residues were not retained inthis study as cotton and wheat residues are used by the farmers ofthis region as a source of fuel and cattle feed, respectively. Residuesof the respective crops were retained on the soil surface at harvestunder all residue retention plots.

2.3. Crop management

Bt-cotton hybrid ‘Bollguard II Nikki’ was sown manually byMay-end each year, at 70 cm × 50 cm and harvested in the secondfortnight of November. In all years and under all plots, cotton wasmanually seeded by dibbling method. Wheat cv. ‘HD 2932’ wassown by November-end using seed drill at 23 cm row spacing. Azero-till seed-cum-fertilizer drill was used for wheat sowing onflat surface, while a bed planter was used for sowing under theraised-bed system. A common dose of 100 kg N + 60 kg P2O5 + 40 kgK2O ha−1 was applied to cotton, of which, P and K were appliedas basal along with 50% N, and the remaining N was given afterone month of the crop growth. Similarly for wheat, a common doseof 120 kg N + 60 kg P2O5 + 40 kg K2O ha−1 was applied, of which Pand K were applied as basal along with 50% N through a seed-cum-fertilizer drill or a bed planter, while the remaining N wastop-dressed in two equal splits (after first and second irrigation).During top dressing, fertilizers were broadcasted and care wastaken so that the fertilizers were mainly targeted on the crop rows.

In the first year before the initiation of the experiment, wheatwas harvested from the experimental plots and wheat residueswere retained in the PBB + R or PNB + R plots. Wheat straw yieldof 2009–2010 (the immediate past crop) was ∼6.5 Mg ha−1. It wasestimated that in all years, about 4.5% of wheat straw remainedas stubble in the CT and other residue removal plots. Similarly, asstated earlier, about 40% of wheat straw was returned in the residueretention plots in cotton in all years. In the second year, wheatresidues (40% of ∼6.5 Mg ha−1 ∼2.6 Mg ha−1) were retained in thenewly introduced ZT + R plots. Thus, the cumulative (in three years)estimated amounts of wheat residues returned to cotton crop were0.96, 0.89, 8.01, 0.94, 8.68, 0.60 and 5.23 Mg ha−1 in the plots underCT, PNB, PNB + R, PBB, PBB + R, ZT and ZT + R, respectively. In wheat,it was estimated that about 20% of cotton stover yield was returnedin the residue retention plots in all years. Thus, the cumulative (in

T.K. Das et al. / Field Crops Research 158 (2014) 24–33 27

Tabl

e

1Tr

eatm

ent d

etai

ls

and

plot

desi

gn.

Trea

tmen

ts

Trea

tmen

tno

tati

ons

Trea

tmen

tde

scri

ptio

n

Cott

on

Whe

at

Tilla

ge

prac

tice

Bed

type

Resi

due

rete

ntio

nRo

w

to

row

spac

ing;

dist

ance

of

the

first

row

from

the

furr

ow

(cm

)

Tilla

ge

prac

tice

Bed

type

Resi

due

rete

ntio

nRo

w

to

row

spac

ing;

dist

ance

of

the

first

row

from

the

furr

ow

(cm

)

CT-fl

at

bed

CT

Conv

enti

onal

tilla

geFl

at

beds

No

70

Conv

enti

onal

tilla

geFl

at

beds

No

22.5

ZT-p

erm

anen

t nar

row

bed

PNB

Zero

tilla

geN

arro

w

bed

(40

cm

bed

and

30

cm

furr

ow)

No

70; 2

0

Zero

tilla

ge

Nar

row

bed

(40

cm

bed

and

30

cm

furr

ow)

No

13.0

; 7.0

ZT-p

erm

anen

t nar

row

bed

+

resi

due

PNB

+

R

Zero

tilla

ge

Nar

row

bed

(40

cm

bed

and

30

cm

furr

ow)

Yes;

abou

t 30%

whe

at

resi

due

70; 2

0

Zero

tilla

ge

Nar

row

bed

(40

cm

bed

and

30

cm

furr

ow)

Yes;

abou

t 20%

cott

on

resi

due

13.0

; 7.0

ZT-p

erm

anen

t bro

ad

bed

PBB

Zero

tilla

ge

Broa

d

bed

(100

cm

bed

and

40

cm

furr

ow)

No

70; 1

5

Zero

tilla

ge

Broa

d

bed

(100

cm

bed

and

40

cm

furr

ow)

No

21.5

; 7.0

ZT-p

erm

anen

t bro

ad

bed

+

resi

due

PBB

+

R

Zero

tilla

ge

Broa

d

bed

(100

cm

bed

and

40

cm

furr

ow)

Yes;

abou

t 30%

whe

at

resi

due

70; 1

5

Zero

tilla

ge

Broa

d

bed

(100

cm

bed

and

40

cm

furr

ow)

Yes;

abou

t 20%

cott

on

resi

due

21.5

; 7.0

a ZT-

flat b

ed

+

resi

due

ZT

+

R

Zero

tilla

ge

Flat

beds

Yes;

abou

t 30%

whe

at

resi

due

70

Zero

tilla

ge

Flat

beds

Yes;

abou

t 20%

cott

on

resi

due

22.5

a ZT-

flat b

ed

ZT

Zero

tilla

ge

Flat

beds

No

70

Zero

tilla

ge

Flat

beds

No

22.5

aIn

trod

uced

from

the

seco

nd

year

of

the

expe

rim

ent.

three years) estimated amounts of wheat residues returned to cot-ton crop were 0, 0, 6.20, 0, 6.22, 0 and 4.32 Mg ha−1 in the plotsunder CT, PNB, PNB + R, PBB, PBB + R, ZT and ZT + R, respectively.

Herbicide gylphosate (N-(phosphonomethyl)glycine) wassprayed at 0.5 kg ha−1 in the zero-till plots about a week beforesowing of both crops. Further, pendimethalin (N-(1-ethylpropyl)-2,6-dinitro-3,4-xylidine) was sprayed at 0.75 kg ha−1 in cottonwithin 2–3 days of sowing. In wheat, isoproturon (N,N-dimethyl-N′-[4-(1-methylethyl)phenyl]urea) at 1.0 kg ha−1 was applied as apost-emergence herbicide, at 30 days after sowing. In addition, onemanual weeding was also performed in cotton at 40 days after sow-ing, while no manual weeding was required in wheat. Sucking pestsand bollworms were observed in cotton. However, no significantdifferences in the population of these two insects in different treat-ments were recorded. Among sucking insects, leafhopper (Amrascabiguttula biguttula), whitefly (Bemisia tabaci) were the major pests.Population of other insects like red cotton bug and aphids wasnot severe. Spraying of imidacloprid (1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-2-imidazolidinimine) and triazophos (O,O-diethyl-o-(1-phenyl-1H-1,2,4-triazol-3-yl)phosphorothioate)were performed for management of leafhoppers and whiteflies,respectively.

2.4. Measurement of yield and yield attributes

Yield attributing parameters for cotton, i.e. plant height (cm),leaf area (cm2 m−2); number of bolls plant−1 and number ofbranches plant−1 were recorded using 1 m2 quadrate from threeplaces in each plot at different stages of observation. At matu-rity, cotton was harvested manually about 2 cm above the groundlevel. Cotton was harvested in the second week of October eachyear, whereas wheat was harvested with a combine about 20 cmabove the ground level in the second week of April in all years.Seed yields of cotton and wheat were reported at 12% moisturecontent. Straw weight was determined after oven-drying at 70 ◦Cto a constant weight and expressed on an oven dry-weight basis.Yields of seed cotton and wheat grain as well as straw/stoverwere taken from the net plot area after discarding the borderrows. In each treatment, there were 12 rows for narrow-beds andsix rows for broad-beds. For cotton and for narrow-beds (rowto row spacing = 0.7 m), central four rows constituting 5 m lengthwas harvested for yield measurement. Thus, the net plot area fornarrow-beds was 14 m2 (2.8 m × 5.0 m). For broad-beds (row to rowspacing = 1.4 m) two rows constituting 5 m length was harvestedfrom the net plot area of 14 m2. For wheat and for narrow-beds,four central beds with 3 wheat rows in each bed (= 12 wheat rows)were harvested from a net plot area of 14 m2 (2.8 m × 5.0 m) netplots. For broad-beds, wheat yield measurements were taken fromtwo central beds with 5 wheat rows in each bed (= 10 wheat rows)from the net plot area of 14 m2. For ZT/CT plots (where conven-tional flat sowing was done), both cotton and wheat were harvestedfrom an area of 2.8 m × 5.0 m for yield measurements. Thus, forflat sown ZT/CT plots, four cotton rows and 12 wheat rows wereharvested.

Seed cotton and wheat yield was individually recorded. Toexpress the overall impact of treatments in terms of compara-ble yield data, the seed cotton yield was converted into wheatequivalent yield (WEY) following Bhattacharyya et al. (2010). Theconverted seed cotton yield of a year was then added to the actualyield of wheat of that year to obtain WEY. Therefore, WEY expressestotal yield (productivity) for the cotton–wheat crop sequence dur-ing 2010–202011 to 2012–2013 (3 yrs). It is the yield of wheatplus yield of seed cotton expressed in terms of wheat yield basedon monetary value of seed cotton and wheat of the respectiveyears.

28 T.K. Das et al. / Field Crops Research 158 (2014) 24–33

2.5. Measurement of irrigation water, total water applied andwater productivity

In 2011–2012, eight irrigations for cotton and five irrigations forwheat, excluding the pre-sowing irrigation, were applied. Whereas,in 2012–2013, nine irrigations for cotton and five irrigations forwheat were applied. The irrigation water depth applied to eachexperimental plot was measured on an average four times duringeach irrigation period using a digital velocity metre and the wet-ted area of the field channel. A rating curve was generated at thebeginning of the experiment, showing the relationship betweenflow depth and discharge in the main channel. Then an exponen-tial equation was developed. Afterwards, flow depth was measuredat the time of irrigation in the channel and corresponding dischargewas determined using either the rating curve or the developedexponential equation. Irrigation water depths indicated by the soilmoisture deficit (SMD) in each treatment was calculated using soilmoisture content before irrigation and root zone depth of plants,besides soil bulk density and time taken to fulfil the SMD, using Eq.(1) (Michael, 2008)

SMD = (!Fc − !i) × DRZ × Bd (1)

where SMD is the soil moisture deficit (mm), !Fc is the soil watercontent at field capacity (%), !i is the soil water content beforeirrigation (%), DRZ is the root zone depth (mm), Bd is the soil bulkdensity (Mg m−3). Soil moisture content at any time was mea-sured by a TDR (time domain reflectometer) that was calibratedpreviously using the gravimetric method. Daily rainfall data werecollected from a rain gauge located at about 500-m away from theexperimental plots. Effective rainfall was calculated using standardmethods given by FAO and then total amount of water appliedwas computed as the sum of water applied through irrigationsand effective rainfall. Water productivity (kg grains ha−1 mm−1 ofwater) was computed using Eq. (2) as given by Bhushan et al.(2007):

total water productivity = grain yield (kg ha−1)total water applied (mm)

(2)

2.6. Labour use

Machine and human labour uses were recorded in both cottonand wheat for each treatment and for each field operation, viz.tillage (for conventionally tilled plots), seeding, irrigation, fertil-izer and pesticide application, weeding, harvesting, and threshing.For human labour, 8 h were considered equivalent to 1 person day,whereas, for tractor-drawn machines, time taken to complete afield operation such as tillage, seeding, fertilizer application andharvesting was recorded and expressed on an ha basis.

2.7. Economic analysis

Cost of cultivation under various treatments was estimated onthe basis of approved rates for inputs fixed by the IARI, New Delhi.The input costs include costs of seed, pesticide, mineral fertili-zers, and the hiring charges of human labour and machines forland preparation, irrigation, fertilizer application, plant protection,harvesting, and threshing. Measurement also included the cost ofresidues (here, cost of ∼2 Mg cotton and ∼2 Mg wheat residues)in the residue retained plots. Gross returns were calculated on thebasis of minimum support price (MSP) offered by Government ofIndia for cotton and wheat seeds of all years. Net income was calcu-lated as the difference between gross income and total cost. Systemproductivity in terms of wheat equivalent yield was calculated byadding the seed yield of cotton (in terms of wheat equivalent yieldcalculated using MSP of both crops) and wheat in each year.

2.8. Statistical analyses

Analysis of variance (ANOVA) was done to determine treatmenteffects (Gomez and Gomez, 1984). Tukey’s honestly significant dif-ference test was used as a post hoc mean separation test (P < 0.05)using SAS 9.1 (SAS Institute, Cary, NC). The Tukey procedure wasused where the ANOVA was significant.

3. Results

3.1. Yield attributes of cotton and wheat

As all treatments were effective since the second year of theexperiment, mean (of last two years of the study) values of all yieldattributes of both crops are presented and discussed. Based on lasttwo years’ mean data, plots with PBB + R had significantly highernumber of cotton bolls plant−1 and number of cotton branchesplant−1 than CT plots (Table 2). All CA plots had similar cottonplant height at 90 days after sowing and leaf area plant−1 and themean (of last two years) values were significantly more than thoseunder CT plots. However, wheat yield attributes were not, in gen-eral, impacted by the CA practices (Table 2). Only plots with ZT hadhigher spikes m−2 than all other plots, excepting the PBB plots.

3.2. Grain yield, straw yield and the aboveground biomassproductivity

Right from the first year, the plots under PBB + R had signifi-cantly higher cotton seed yield and cotton aboveground biomasscompared with CT plots (farmers’ practice), resulting in a highersystem productivity (wheat equivalent yield; WEY) (Table 3). How-ever, wheat grain yield as well as biomass productivity in the plotsunder PBB + R and CT were similar in the first year. Both CT andPNB treated plots had similar WEY in the first year. In the secondand third year of the experiment, similar trends were also observedfor seed cotton yield and cotton aboveground biomass, with a littlemodification. The newly introduced treatment, ZT + R, performedsimilar to PBB + R in terms of both cotton seed yield, wheat grainyield and the system productivity in the second and third years ofthe experiment (Table 3). However, ZT plots (the other new treat-ment in the second year), although performed similarly to the ZT + Rplots (except for the wheat yield in the second year of the exper-iment), yielded nearly 15% less seed cotton yield compared withPBB + R in the third year. Similarly, plots under ZT had about 19%less wheat yield than PBB + R plots in the second year (Table 3).

Despite tillage systems had significant impacts; residue man-agement effects were not visible in terms of seed/grain yields overthe years. Only in the second year (2011–2012), plots under ZT + Rhad ∼11% higher wheat grain yield than ZT plots (4.0 Mg ha−1) andPBB + R had ∼14% higher wheat yield than PBB. Mean yield of lasttwo years of the experiment showed that plots under PBB + R hadabout 36% higher mean seed cotton yield compared with CT plots(∼2.7 Mg ha−1) and PBB plots had 20% higher mean seed cottonyield than CT plots (Fig. 2). However, plots under PNB, PNB + R, PBBand ZT had similar mean seed cotton productivity. Again plots withPBB + R had nearly 20% higher mean seed cotton yield than PNBplots (Fig. 2).

Mean (of last two years) wheat productivity was lesser affectedby CA than mean seed cotton yield. Only PNB + R and PBB + R plots,that yielded about 4.8 Mg ha−1 wheat grain, had significantly highermean wheat grain yields than both CT and ZT plots (Fig. 2). Thusthe mean system productivities (in terms of WEY) of ZT, ZT + R,PBB + R and PNB + R plots were similar. In fact, the system produc-tivities (WEY) of the PBB + R plots during the first, second and thirdyears were highest (Table 3), and PBB + R had significantly higher

T.K. Das et al. / Field Crops Research 158 (2014) 24–33 29

Table 2Yield attributes (mean values of 2011–2012 and 2012–2013) of the cotton and wheat crops.

Treatments* Cotton Wheat

Plant height (m) at 90days after sowing

Leaf areaplant−1 (m2)

No. of bollsplant−1

No. of branchesplant−1

Spikes m−2 Grain Spike−1 Test weight (g)

CT 1.35b 0.98b 40.3c 16.5b 314.6b 42.1a 40.8aPNB 1.53ab 1.54ab 44.4b 17.2b 317.3b 43.3a 41.1aPNB + R 1.67a 1.53ab 40.5c 18.6ab 312.8b 44.2a 41.2aPBB 1.64a 1.66a 39.9c 19.8a 344.4ab 42.1a 41.1aPBB + R 1.60ab 1.53ab 50.0a 20.6a 342.8ab 42.2a 40.9aZT + R 1.64a 1.71a 41.3bc 17.0b 324.4b 41.5a 41.1aZT 1.48ab 1.66a 41.9bc 21.0a 360.6a 40.9a 41.9a

*See Table 1 for the treatment details. Means followed by a similar lowercase letter within a column are not significantly different (at P < 0.05) according to Tukey’s HSD test.

Table 3Productivity (Mg ha−1) of cotton, wheat and system productivity (Mg ha−1) in terms of wheat equivalent yield (WEY) as affected by tillage, bed planting and residuemanagement practices in the western Indo-Gangetic Plains.

Treatments* 2010–2011 2011–2012 2012–2013

Seed cottonyield

Wheat grainyield

Systemproductivity(WEY)

Seed cottonyield

Wheat grainyield

Systemproductivity(WEY)

Seed cottonyield

Wheat grainyield

Systemproductivity(WEY)

CT 2.44c (8.13c)a 4.85a (7.54a) 10.30b 2.73c (8.48c) 4.29b (7.14ab) 11.16c 2.70c (10.17ab) 4.46b (6.31b) 12.25bPNB 2.71bc (9.34ab) 4.55a (6.16b) 10.60b 3.10bc (9.16c) 4.37b (6.97ab) 12.17bc 3.08ab (10.76a) 4.83ab (6.86b) 13.72abPNB + R 2.96b (9.25ab) 4.61a (6.55ab) 11.23ab 3.33b (11.11a) 4.60ab (7.78a) 12.97b 3.38a (10.62a) 4.98a (8.04a) 14.74aPBB 3.13ab (10.09a) 4.82a (7.38a) 11.81ab 3.42ab (10.84a) 4.19bc (6.88b) 12.80b 3.11ab (9.98ab) 4.75ab (6.95b) 13.72abPBB + R 3.28a (9.65a) 4.85a (7.41a) 12.16a 3.93a (11.20a) 4.77a (6.57b) 14.67a 3.46a (10.27ab) 4.89a (6.83b) 14.88aZT + R – – – 4.00a (10.96a) 4.44ab (7.66a) 14.50a 3.21ab (9.89ab) 4.73ab (7.87a) 13.99abZT – – – 3.95a (10.76ab) 4.00c (6.64b) 13.93ab 3.02bc (9.65b) 4.63ab (8.31a) 13.35ab

a Data in parentheses indicate stover (cotton)/straw (wheat) yields.* See Table 1 for the treatment details. Means followed by a similar lowercase letter within a column are not significantly different (at P < 0.05) according to Tukey’s HSD

test.

WEY values than CT (farmers’ practice) in all three years. Simi-larly, PBB + R plots had also higher WEY values than PNB plots inthe first and second years, but not in the third year. Plots underPBB + R (yielded nearly 14.8 Mg ha−1 WEY) had nearly 11, 14 and26% higher mean (of last two years) WEY than PBB and PNB andCT plots, respectively. Farmers’ practice (CT) had significantly lessmean system productivity than all plots.

Both tillage and residue management practices had significantimpacts on cotton and wheat straw yields and there were no con-sistent trends in cotton or wheat stover yields for a treatment overthe years (Table 3). For instance, PNB plots had significantly lesscotton stover yield in the second year than PBB + R plots, but hadsimilar cotton stover yield to PBB + R plots, in the third year of theexperiment. PNB plots had less wheat straw yield in the first yearcompared with PBB + R plots, but had similar straw yields in the

Fig. 2. Impacts of conservation agricultural practices on mean (of last two years ofthe experiment; 2011–2013) seed cotton yield, wheat grain yield and cotton–wheatsystem productivity in the upper Indo-Gangetic Plains. See Section 2 for treatmentdetails. Bars followed by a similar letter for a management practice within a columnare not significantly different at P < 0.05 level of significance according to Tukey’sHSD mean separation test.

subsequent years. All ZT plots had significantly higher cotton stoveryields than CT plots in the first year of the experiment (Table 3).But wheat straw yield was unaffected by the treatments in theinitial year. In the second year, plots under PBB + R had the high-est cotton stover yield that was significantly higher than CT andPNB plots (Table 3). However, during that year, PNB + R had higherwheat straw yield than plots with PBB and PBB + R plots. Similartrend continued in the third year as well with the exception thatplots under PBB + R had similar cotton stover yield to ZT-NB and ZT-NB + R plots. Both PBB + R and PBB plots had less wheat straw yieldsthan ZT/ZT + R plots, indicating broad-beds had less stover/strawyields than flat beds in the advancing years of cultivation.

3.3. System water productivity

Total water applied (including the rainwater) in thecotton–wheat system in both years were highest for the CTplots, whereas PBB + R plots received the least water in both years(Table 4). Residue retention invariably reduced the amount ofwater applied in both years. For instance, PBB + R plots received64 mm less water than PBB plots during 2011–2013 (last twoyears of the study), PNB + R received 42 mm less water than PNBand ZT + R received 138 mm less water than ZT plots (Table 4).Again, there was about 3 and 10% water saving in the PBB plotscompared to PNB and ZT plots, respectively, and about 13 and14% water savings with PBB + R compared to ZT and CT plots.Highest productivity with PBB + R, as discussed in the previoussections, and least water consumption yielded the highest meansystem water productivity in the plots under PBB + R (∼12.6 kgwheat equivalent ha−1 mm−1). This highest mean system waterproductivity was significantly higher than all treatments andmost importantly about 48% higher than the farmers’ practice inthe region (Table 4). Partial residue retention (about 20% for thecotton crop and 30% for the wheat crop) had significant impact onimproving mean (of two years) system water productivity in both

30 T.K. Das et al. / Field Crops Research 158 (2014) 24–33

Table 4Impacts of tillage, bed planting and residue management practices on water productivity (kg wheat grain ha−1 mm−1) under the cotton–wheat system.

Treatments* 2011–2012 2012–2013 Mean of two years

Total water appliedin the system (mm)

System waterproductivity

Total water appliedin the system (mm)

System waterproductivity

Total water appliedin the system (mm)

System waterproductivity

CT 1331 8.38d 1417 8.65d 1374 8.52dPNB 1208 10.07c 1297 10.58b 1253 10.33cPNB + R 1181 10.98bc 1282 10.50bc 1232 11.24bPBB 1160 11.03bc 1260 10.89b 1210 10.96bcPBB + R 1130 12.98a 1222 12.18a 1176 12.58aZT + R 1247 11.62b 1312 10.66b 1280 11.14bZT 1310 10.63bc 1387 9.62c 1349 10.13c

* See Table 1 for the treatment details. Means followed by a similar lowercase letter within a column are not significantly different (at P < 0.05) according to Tukey’s HSDtest.

PBB and PNB plots compared with residue removal under theseplots.

3.4. Economics of cultivation

Costs of cultivating cotton and wheat in a year were significantlyhigher in the plots under all residue retained plots compared withCT during 2011–2012 and 2012–2013. However, the net returnsin 2011–2012 were higher in the PBB + R, ZT + R and ZT plots thanother treatments. In 2011–2012, plots under PBB + R had 23% highernet returns than PNB + R plots. Contrarily, in 2012–2013, PBB + Rand PNB + R had similar net returns. Mean (of two years) valuesindicate that residue retained plots had significantly higher costsof cultivation. However, PBB + R plots had the highest net returnsthat was 36 and 13% higher than CT and PNB plots, but was similarto all other treatments (Table 5).

4. Discussion

In this region under the cotton–wheat system, the sticks of cot-ton are pulled out, removed from the field and are used as fuel.The wheat straw is either removed from the fields or is burnt dueto shortage of time between harvesting of wheat crop (secondfortnight of April) and sowing of the cotton crop (first to sec-ond fortnight of May). Moreover, in these semi-arid environmentstermites do attack leftover crop residues and in some instances dis-ease prevalence force the farmers to burn or remove crop residuesfrom their fields. Thus entire biomass removal along with inten-sive tillage causes loss of soil carbon and other nutrients (Beriet al., 2003) and development of water repellency in soil layers(Passioura, 2002; Singh et al., 2005). As a result, productivity ofthe cotton–wheat system has become static or started declining(Jalota et al., 2008). To address these issues, this experiment wasconducted on a sandy clay loam soil under different conserva-tion agricultural practices, where all principles of CA (zero tillage,

residue retention, crop rotation and controlled traffic) along withbed planting were employed.

In accordance to the first hypothesis, ZT with permanent bedplanting (both narrow and broad beds) and residue retentionresulted in higher seed cotton yield and cotton–wheat systemproductivity compared with farmers’ practice (CT and no residueaddition) for all years. However, wheat grain yields in the plotsunder PBB + R and PNB + R were significantly higher compared withCT only in the third year of the experiment. Both mean (of last twoyears of the experiment) system water productivity and mean netincome of the above-said PBB + R and PNB + R treatments were sig-nificantly higher than CT, indicating that the first hypothesis wasaccepted. In the initial year, despite wheat residue addition, seedcotton yield was not significantly higher under PBB + R comparedwith PBB or under PNB + R compared with PNB. Similarly, despiteboth wheat and cotton residue addition, wheat grain yields weresimilar under PBB + R and PBB plots, and under PNB + R and PNBplots. This trend continued in all years for seed cotton and wheatgrain yields. However, the combination of broad-bed and residueretention had significant impacts right from the first year onwards.For instance, plots under PBB + R had significantly higher seed cot-ton yield than PNB or PNB + R plots in the initial year.

The results explicitly indicate that the best treatment (PBB + R)had 14% less water requirement but produced 48% higher systemproductivity (in terms of WEY) than the farmers’ practice/CT. Simi-larly, in the irrigated areas of northwest Mexico, farmers who grewwheat using the planting system on beds obtain 8% higher yield,used approximately 25% less irrigation water compared to thoseplanted conventionally tilled wheat on the flat beds using floodirrigation (Aquino, 1998). Like us, Jalota et al. (2008) reported thatremunerability of the cotton–wheat system was more with a com-bination of reduced tillage in cotton and minimum tillage in wheatthan CT, in Punjab, India. Significant improvements in cotton lintyields with minimum tillage systems has also been reported byConstable et al. (1992) and Hulugalle et al. (1997) on irrigated

Table 5Impacts of tillage, bed planting and residue management practices on cost of cultivation and net returns under an irrigated cotton–wheat system in the western Indo-GangeticPlains.

Treatments* 2011–2012 2012–2013 Mean of two years

Cost of cultivation(INR/ha)a

Net returns(INR/ha)

Cost of cultivation(INR/ha)

Net returns(INR/ha)

Cost of cultivation(INR/ha)

Net returns(INR/ha)

CT 67522b 75903d 69272b 125428c 68397b 100666cPNB 65722b 90710bc 65872b 151270ab 65797b 120990bPNB + R 74722a 91988bc 76372a 158240a 75547a 125114abPBB 65722b 98717b 65872b 155052ab 65797b 126885abPBB + R 74722a 113724a 76372a 159823a 75547a 136774aZT + R 74122a 112249a 75772a 149371ab 74947a 130810abZT 65122b 113863a 65272b 145311b 65197b 129587ab

a 1 USD ∼ 55 INR (2011–2012) and 60 INR (2012–2013).* See Table 1 for the treatment details. Means followed by a similar lowercase letter within a column are not significantly different (at P < 0.05) according to Tukey’s HSD

test. INR = Indian rupee.

T.K. Das et al. / Field Crops Research 158 (2014) 24–33 31

vertisols of Australia. However, significant cotton yield improve-ments, net returns and system water productivity with permanentbeds and residue retention have rarely been reported earlier. Yieldimprovements in ZT systems with residue retention over CT sys-tems could be due to the compound effects of many factors, namely,additional nutrient, reduced competition to resources due to lowerweed density, improved soil physical properties and water regimes,better water extraction, aeration and nutrient use rather than CT(Unger and Jones, 1998). Soil structure affects crop yield through acomplex of root-based mechanisms that in turn affect the above-ground biomass (Passioura, 2002). Continuous ZT with residueremoval often lead to poorer soil structural quality (more com-pact) and yield reduction (Munkholm et al., 2003). Crop residuesare direct sources of organic C and positive effects of crop residueson improvements in SOC, N and other nutrients have been noted byseveral researchers (Lal, 1997; Yadvinder-Singh et al., 2004; Kunduet al., 2007; Das et al., 2013; Bhattacharyya et al., 2013a). These arethe major causes of higher yields in the residue retained plots thanthe plots with residue removal.

Despite residue retention, wheat yields were not affected inboth first and third year of the experiments. Similar or some-times higher wheat yields with tillage treatments in the initialyears might be due to favourable effect of the tillage practices onhastening of organic matter decomposition and higher nutrientavailability (Nehra et al., 2005), enhanced root growth (Jorge et al.,1984) and breaking of hard setting and mechanical loosening foroptimum crop growth (Lal, 1989). It has been reported that duringthe initial years, at the establishment of the permanent bed plant-ing system, crop yields can be reduced as the net N immobilizationis increased (Yadvinder-Singh et al., 2004) by microorganisms toundergo residue decomposition. However, the results of this studyindicate that the yields were not reduced, rather increased in thesecond year, ZT + R plots had higher wheat yield than ZT and PBB + Rhad higher wheat grain yield than PBB plots. In the third yearalso, residue retained plots had numerically higher yields thanresidue removal plots. This phenomenon calls for detailed inves-tigation on the N availability and soil health in the cotton–wheatsystem under CA and probable reduced N application effects oncrop productivity, after crop yields become stable or higher underCA (Sayre and Hobbs, 2004). Limon-Ortega et al. (2000) and Fahonget al. (2004) also observed that after some initial years, the bedplanting increased the N use efficiency compared with conven-tional planting when the appropriate management practices wereadopted.

In general, bed planting with residue retention had significantlyhigher net primary productivity (aboveground biomass yield) com-pared with conventional flat planting and the cotton crop (a hybridBt-cotton) responded very well to bed planting in this region.Despite reduced population under bed planting compared to con-ventional planting (as in each 70 cm width under narrow bedplanting there were three wheat rows versus four wheat rowsunder flat/conventional planting), plots under PNB had similar seedcotton yields, wheat yields and system productivities in all years,excepting the latter treatment had higher seed cotton yield thanthe former in the third year of the study. The beneficial effects ofCA on cotton yield confirm the earlier observations that residueretention produced higher seed cotton yield (Prasad and Power,1991; Nehra et al., 2005). Prasad and Power (1991) also reportedbeneficial effect of retaining crop residues in the field in a widevariety of crops, which increase organic matter, aggregation, waterholding capacity and infiltration (Oades, 1984; Swift and Sanchez,1984; Bhattacharyya et al., 2006, 2008).

Although there were 6 wheat rows within 140 cm width under anarrow-bed plot (PNB or PNB + R) compared to 5 wheat rows within140 cm width under a broad-bed plot (PBB or PBB + R), there wereno significant wheat yield differences due to the bed configurations.

This indicates that under broad beds, wheat had more numbers oftillers per unit area than the plots with narrow beds. In fact, thenumber of spikes m−2 were about 8% higher under PBB plots thanPNB plots (Table 2), but the differences were not significant. Theseresults are very interesting, and further studies on respiration rates,photosynthesis, light interception, radiation use efficiency vis-a-vis crop geometry under different bed configurations would helpunderstand the net primary productivity better. Hence, the sec-ond hypothesis that ZT with broad-beds (PBB) would have highersystem productivity and water productivity than ZT with narrow-beds (PNB) was partially accepted as the results indicate that inall years, PBB plots had similar seed cotton and wheat grain yields(and thus the mean system productivities were similar) to the PNBplots. Contrarily, seed cotton yield was significantly higher in thePBB + R plots than PNB + R in both the first and second years of thestudy and the system productivity was higher in the second yearunder PBB + R plots than PNB + R. This trend could be due to the factthat under residue retained condition, the moisture storage andavailability was better under broad-beds than that in the narrow-beds. In fact, the water requirement under PBB + R plots was lessthan PNB + R plots and the combination of less water require-ment and yield increase led to a significantly higher mean systemwater productivity under PBB + R compared with PNB + R plots(Table 4). It was also observed that PBB + R plots had larger cottonroot length density and higher root water uptake compared withPNB + R plots after two years of study (Mishra et al., unpublisheddata).

5. Conclusion

The major aim of this study was to evaluate the impacts ofpromising conservation agricultural practices on crop productiv-ity, water productivity and net returns during a three year oldcotton–wheat cropping system in the western IGP. Results indi-cate that permanent beds with residue addition (PBB + R plots) hada gain in the mean (of last two years) cotton–wheat system pro-ductivity by ∼3.1 Mg wheat equivalent yield ha−1 yr−1 (with nearly1.4 Mg ha−1 yr−1 increase in cotton and wheat seed yields) over thefarmers’ practice (CT). The PBB + R plots also used 14% less waterbut resulted in 48% more mean system water productivity and 36%higher net income compared with CT. Plots under PBB + R also hadsignificantly higher mean water productivity than both PNB + R andZT + R plots and similar but numerically higher net returns and sys-tem productivity than both PNB + R and ZT + R plots, indicating thesuperiority of the PBB + R treatment. The above-said managementpractice under the cotton–wheat system had about 10% higher costof production than the farmers’ practice, mainly due to the residue(that was retained) cost. In reality the cost of production underCA practices would be almost equal or less than CT, as majority ofthe farmers burn the excess residues. However, the added residuehas the potential to improve soil quality gradually and this wouldlikely reduce the mineral fertilizer (especially N) use. Thus, theseresults are of tremendous importance in terms of identificationof a suitable sustainable management practice under a non-ricebased cropping system (here, the cotton–wheat system), and arevery novel in the South Asia. Thus, the said PBB + R package ofpractice has a wide scope for adoption in the cotton–wheat sys-tem of this region and other countries with similar agro-ecologies,where intensive tillage is practised.

Acknowledgements

The authors gratefully acknowledge the support received fromthe different Divisions of the Indian Agricultural Research Institute(IARI), New Delhi for successful conduct of this research work

32 T.K. Das et al. / Field Crops Research 158 (2014) 24–33

under the ‘Challenge Programme on Conservation Agriculture’.The initial support from the International Maize and WheatImprovement Centre (CIMMYT) is gratefully acknowledged.

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