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Crop Protection 26 (2007) 436–447
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Review
A review of resource conserving technologies for sustainablemanagement of the rice–wheat cropping systems of the Indo-Gangetic
plains (IGP)
Raj Guptaa, Ashok Sethb,�
aRice–Wheat Consortium for the Indo-Gangetic Plains, CIMMYT India, NASC Complex, Pusa, New Delhi, IndiabARD Consultants Ltd., Whitedown Lane, Alton, Hampshire, UK
Received 7 September 2005; accepted 10 April 2006
Abstract
Rice and wheat are the staple food crops occupying nearly 13.5 million hectares of the Indo-Gangetic plains (IGP) of South Asia
covering Pakistan, India, Bangladesh and Nepal. These crops contribute more than 80% of the total cereal production and are critically
important to employment and food security for hundreds of millions of rural families. The demand for these two cereals is expected to
grow between 2% and 2.5% per annum until 2020, requiring continued efforts to increase productivity while ensuring sustainability.
Starting from the 1960s, expansion of area and intensification of rice–wheat productions system based on the adoption of Green
Revolution (GR) technologies, incorporating the use of high-yielding varieties, fertilizers and irrigation, led to increased production and
productivity of both these crops. However, continued intensive use of GR technologies in recent years has resulted in lower marginal
returns and, in some locations to salinization, overexploitation of groundwater, physical and chemical deterioration of the soil, and pest
problems. This paper presents findings from recent research on resource conservation technologies involving tillage and crop
establishment options that are enabling farmers to sustain productivity of intensive rice–wheat systems. Field results show that the
resource conserving technologies, an exponent of conservation agriculture, improve yields, reduce water consumption, and reduce
negative impacts on the environmental quality. The paper considers contributions of innovative inter-institutional collaboration in
international agricultural research and socio-economic changes in the IGP countries that led to rapid development and adoption of these
technologies by farmers.
r 2006 Elsevier Ltd. All rights reserved.
Keywords: Crop establishment; RCT; Rice; Tillage; Water; Wheat
1. Introduction
In South Asia, Bangladesh, India, Nepal, and Pakistan,have devoted nearly half of their total land area of 401.72million hectare (mha) to feed and provide livelihoods for1.8 billion people. Rice and wheat are the staple food cropsand contribute more than 80% of the total cerealproduction. Over about 13.5mha of the Indo-Gangeticplains (IGP), spread over the four countries, these twocrops are grown in rotation, with other crops such asmaize, pigeon pea, sugarcane, and lentil substituting either
e front matter r 2006 Elsevier Ltd. All rights reserved.
opro.2006.04.030
ing author.
esses: [email protected] (R. Gupta), [email protected]
the rice or wheat crop in some years (Ladha et al., 2000;Gupta et al., 2003; Hobbs and Morris, 1996; Woodhead etal., 1993, 1994; Timsina and Connor, 2001; Abrol et al.,2000; Razzaque et al., 1995; Huke et al., 1993a–c). Therice–wheat production systems are fundamental to employ-ment, income, and livelihoods for hundreds of millions ofrural and urban poor of South Asia (Paroda et al., 1994).Despite priority given to rice and wheat research by the
national institutions during the 1940s, 1950s and early1960s, only limited advances were made in productivity.This, combined with unpredictable climatic conditions,meant that South Asia increasingly relied on imported foodgrains to feed its growing population. The 1960s alsowitnessed establishment of an international agriculturalresearch system, known as the Consultative Group for
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Fig. 1. Map showing the Indo-Gangetic Plains transects according to
Rice–Wheat Consortium (source: RWC, New Delhi).
R. Gupta, A. Seth / Crop Protection 26 (2007) 436–447 437
International Agricultural Research (CGIAR). The institu-tions established by the CGIAR included the InternationalRice Research Institute (IRRI) and Centro Internacionalde Mejoramiento de Maize and Trigo (CIMMYT) whichgave major boost to international research on rice andwheat, respectively in close partnerships with the nationalinstitution, including those in South Asia. The majorobjective set for this innovative network of national andinternational working in close collaboration with eachother was to develop new varieties of rice and wheat toimprove productivity. Availability of new varieties, re-sponsive to much higher rates of fertilizer use, andexpansion of irrigation systems, led to dramatic increasesin productivity and total production of rice and wheat inAsia during late 1960s, which continued through the 1970s,1980s and early 1990s. Other contributing factors toincreased production included: suitable thermal regimesfor rice and wheat cultivation; expansion of land underrice–wheat cropping systems; and an increasing demandfor staple cereals from the rising population with higherincomes. Although since the 1960s, the growth rate in theSouth Asian cereal production (on an average wheat 3.0%,rice 2.3% per annum) has kept pace with populationgrowth (Pingali and Heisey, 1996), evidence is nowemerging that continuous cultivation of rice and wheat islowering soil fertility and organic matter content (Yadav etal., 1998), depleting ground water resources in tube-wellirrigated areas (Gulati, 1999), exacerbating weed problem,including resistance to herbicide, (Malik and Singh, 1995;Malik, 1996; Malik et al., 1998), and pest problems (Pingaliand Gerpacio, 1997). In addition, micro-nutrient deficien-cies, e.g. zinc, boron, sulfur, have also started appearing asa serious concern (Nayyar et al., 2001). In view of theincreasing threat to sustained incremental food productionin the IGP, in 1994, the national and the internationalpartners of the CGIAR established the Rice–WheatConsortium (RWC) as an eco-regional initiative of theCGIAR. The main mandate of the RWC was addressconcerns related to sustainability of the rice–wheatproduction systems and to promote technologies that helpfarmers to reduce cost of production. This paper reviewsthe outcome of the work supported by RWC to developresource conserving technologies (RCTs) and their benefitsin terms of improved productivity, farm-gate incomes andpotential for mitigation of adverse environmental impacts.The paper also examines the role played by differentstakeholders in the rapid dissemination of RCTs.
2. IGP: agro-ecological conditions
The IGP comprises the Indus and the Gangetic plainscovering Pakistan, India, Nepal and Bangladesh. In termof vegetation, IGP is a relatively homogeneous ecologicalregion. The IGP has a continental monsoonal climate. Inthe northwest Indus and Gangetic plains, average annualprecipitation ranges from 400 to 750mm/yr and increasestowards the Bay of Bengal. In the warm and humid easterly
Gangetic plains, annual rainfall is as high as 1800mm/yr.Nearly 85% of the total precipitation is received during themonsoon season from June to September. In the cooler(winter) months between November and February, only afew showers, which is the wheat-growing season (Novem-ber–March). Rice is grown during the warm humid/sub-humid monsoon season (June–October). The calcareousalluvial soils of the semiarid northwest are micaceous andalkaline in reaction, whereas they are slightly acidic in thesub-humid/humid eastern region. Based on physiographic,bioclimatic, and social factors, the region can be sub-divided into five broad transects as shown in Fig. 1 (RWC-CIMMYT, 2003; Rice–Wheat Consortium (RWC), 2005).A brief overview of these transects is given below:
�
Transect 1 lies in the Pakistan Punjab, with a semi-aridclimate, alluvial soils with gentle slopes and gooddrainage (with some pockets of alkali soils and low-quality groundwater). � Transect 2 lies in the Indian States of Punjab, HimachalPradesh and Haryana, with climate and soils similar toTransect 1, except for the topography, which is saucer-shaped, and the diversity of agro-ecosystems is greater.In parts of this transect, irrigated rice (in rotation withwheat) is grown on relatively light sandy loam/loamsoils, and is established before the onset of the monsoon.This results in huge demands for irrigation water andcorrespondingly heavy exploitation of groundwaterreserves to support high irrigation intensity. As a result,in the central areas of Punjab, for example, thegroundwater table shows a decline of 20 cm/yr, withsome places reaching a decline of 100 cm/yr.
� Transect 3 lies in parts of Haryana, western and centralUttar Pradesh, and the Terai regions of India andNepal. It is characterized by a hot sub-humid climate, asaucer-shaped topography, and substantially morediverse agro-ecosystems. In parts of this transect, e.g.,in areas surrounding Karnal in Haryana, irrigated
ARTICLE IN PRESSR. Gupta, A. Seth / Crop Protection 26 (2007) 436–447438
Basmati rice established with the onset of the monsoon.Further east, in western Uttar Pradesh, the presence ofsugarcane mills has led to defined areas for canecultivation and the rice–wheat rotation covers a smallerproportion of the total cultivated area.
� Transect 4 lies in eastern Uttar Pradesh, Bihar andeastern parts of Nepal. It is characterized by a hot sub-humid climate with annual rainfall in the range of1000–1500mm, the presence of low-lying flood-proneareas, periodically changing river courses, and adiversity of rice-based cropping systems. In parts of thisarea, the underground water table is shallow and may beeasily exploited. In this transect, the potential for areaexpansion and yield improvement for rice, wheat andother crops is quite high.
�Table 1
An analysis of the dynamics of 94 IGP districts for the input, output and
total factor productivity growth between the period from (1980–1990) and
(1990–1997)
Growth Input Output TFP
1981–1990 1990–1997 1981–1990 1990–1997 1981–1990 1990–1997
Negative 2 6 0 12 4 23
Stagnating 1 23 5 25 33 40
Low 3 7 4 4 4 6
Moderate 24 16 22 21 18 11
High 64 42 63 32 35 14
Source: NATP (2001–2002).
Transect 5 lies in West Bengal and Bangladesh, with ahot and sub-humid to humid climate, but with evensmaller and more diversified farm holdings, which aremore flood-prone than those of Transect 4. In addition,arsenic contamination of groundwater becomes aserious concern.
Even within these transects there is variability in thespatial incidence of factors influencing productivity. Someexamples include alkali/sodic lands, rising or falling watertables, poor drainage, arsenic-contaminated groundwater,soil micronutrient deficiencies, herbicide-resistant in Pha-
laris minor.
3. The emerging challenges
Over the years, the rice–wheat systems in the north-western part of IGP have become largely mechanized,input-intensive, and dependent on the conjunctive use ofsurface and groundwater. In contrast, the rice–wheatsystems of the eastern IGP have remained largely labor-intensive and less mechanized. Farmers use low inputsbecause of socio-economic constraints and serious pro-blems of drainage congestion and rainwater management.In all parts of the IGP farmers rely on tube-well irrigationto supplement rain water or to meet full water require-ments for crop production (Fujisaka et al., 1994).
Evidence is now emerging that continued intensificationof input use since the adoption of GR technologies isproviding lower marginal returns (Ladha et al., 2000). Atthe same time, it is known that inappropriate use of appliedinputs and overexploitation of natural resource base,principally land and water, is in many situations leadingto secondary salinization in low-quality aquifer zones,groundwater table recession in fresh water aquifer zones,physical and chemical deterioration of the soil and waterquality due to nutrient mining and pollution of groundwater in some locations due to over application ofnitrogenous fertilizers and of environment through cropresidue burning and pesticide use (Byerlee, 1992; Pingaliand Rosegrant, 2001; Murgai et al., 2001; Gupta et al.,2003). Consequently, there are now serious concerns about
the future potential for productivity growth and long-termsustainability of the irrigated rice–wheat systems of theIGP. A recent study has revealed that rice–wheat systemssuffer from stagnation in productivity in spite of largeproduction potential yet to be tapped in large areas ofmiddle and lower Gangetic plains (NATP, 2001–2002). Thetotal factor productivity (TPF) index of the crops was1.4%, 0.9%, 0.43% and 3.1% in trans-, upper- middle- andlower-Gangetic plains, respectively. Data presented inTable 1 points to a significant increase in the number ofdistricts where input, output and TFP growth has turnednegative or stagnated. Thus, the major challenge for SouthAsian countries is to continue to look for technologicalinnovations coupled with socio-economic adjustments andpolicy reforms to sustain increases in productivity andproduction of the rice–wheat systems.
4. The Rice–Wheat Consortium (RWC)
This ecoregional program (EP) of the CGIAR and itsnational partners developed from many years of colla-borative research between CIMMYT, IRRI and theNational Agricultural Research Institutes (NARSs) toimprove rice and wheat production in Bangladesh, India,Nepal and Pakistan (Fig. 2). RWC addresses naturalresource management (NRM) issues, and problems ofagricultural productivity and production within a geogra-phically defined area. It provides a mechanism forcollaboration between the commodity-based internationaland national research institutions working on similarthemes to engage in cropping systems research (Seth etal., 2004). Since inception, the research programs sup-ported by RWC have had the following objectives:
�
Develop technologies for sustainable intensification anddiversification of the rice–wheat systems, includingtillage and crop establishment options for growing riceand wheat in sequence in a systems perspective. � Help to disseminate promising technologies for scaling-up among different regions of the IGP so as to producemore food at less cost and improve livelihoods andcontribute to reduction in poverty.
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RegionalSteering
Committee
RegionalTechnical
CoordinationCommittee
RWCCoordination
Unit
RegionalCoordinator
NationalSteering
Committee
Ntnl. Tech. Coord.Committee
NationalCoordinator
SiteCommittees
SiteTeams
Farmers ofdifferent
socio-economicgroups
LineDepartments
IARCs/ARIs
PrivateInput/Service
Providers
CGIARConvening
Centre(CIMMYT)
Fig. 2. The operational structure of the Rice–Wheat Consortium.
R. Gupta, A. Seth / Crop Protection 26 (2007) 436–447 439
�
Strengthen existing partnerships and assist with capacitybuilding of the national research organizations andprograms.In recent years, development of RCTs for sustainablemanagement of natural resources in rice–wheat systems hasbecome the major focus of the RWC research.
4.1. Research approach
Within the IGP countries (Bangladesh, Pakistan, Nepaland India) research and monitoring activities followed astep-wise approach as under:
�
Field surveys and participatory needs assessment offarm-level constraints to determine priorities (Harring-ton et al., 1992, 1993; Fujisaka et al., 1994; Byerlee,1992; Byerlee et al., 2003; Khan et al., 2004). � Comprehensive analysis of the existing and on-goingresearch information (Kumar and Rosegrant, 1994;Kumar and Mrithyunjaya, 1992; Pingali and Shah,1999; Janaiah and Mahabub Hossain, 2003; Dawe et al.,2000; Sinha et al., 1998; Yadav et al., 2000; Ladha et al.,2003; Pathak et al., 2003; Dawe et al., 2003; Bhandari etal., 2002; Regmi et al., 2002a, b; Singh et al., 2002a, b;Gami et al., 2001; Yadav, 2001).
� Joint planning of work programs with national scientistsand other stakeholders (Rice–Wheat Consortium(RWC), 2000), and
� Participatory research on agronomic and crop manage-ment practices for technology validation (Mehla et al.,2000; Gupta et al 2003; Gill et al 2002; Dhillon et al.,2000a, b).
4.2. The impact pathway
As shown in Fig. 3, the key elements of the impactpathway adopted by RWC included: farmer participatory
research involving all the key stakeholders with emphasison two-way flow of knowledge between the national andinternational partners; applied and adaptive research onagronomic and crop management practices; capacitybuilding of national research and extension systempartners; and encouragement to involvement of NGOsand the private-sector input and service providers intechnology development and dissemination processes. Itis concluded that the adoption of this pathway has not onlyhelped to instil a new paradigm for research–extension–farmer–private sector linkages in the context of the IGPcountries but also accelerated the speed with whichtechnologies were transferred from research to farmers.Greater efforts are now needed to make such approaches aregular feature of the national program planning andimplementation in the participating countries.
5. Key technologies developed for sustainable management
of natural resources
5.1. Tillage and crop establishment
The conventional system for establishment of wheatcrops includes repeated ploughing (6–8 ploughing), culti-vating, planking, and pulverizing of topsoil. This has beensubstituted with direct drilling of wheat using zero-till seeddrills fitted with inverted T-openers to place seed andfertilizers into a narrow slot with only minimal of soildisturbance and without land preparation (Fig. 4). Sub-stitution of conventional tillage with zero or minimumtillage for wheat planting in rice–wheat system, especiallyin the north-western IGP, is a development of regionalsignificance and contributes to the global application ofresource conservation technologies (RCTs) in to a new eco-system. Rice crop is conventionally established as apuddled transplanted crop. Joint efforts of the publicinstitutions and the small-scale private entrepreneurs are
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Knowledge Sharing and
Capacity building
IARCs’Core Programs
Systems ResearchCoordinated by RWC
Researchprograms
Farmers
Participatoryvalidation andrefinements
of technologies
Participatory needsassessment by
NARS/Extension/NGOs
TechnologyDisseminationa
Privateinput/
Serviceproviders
Fig. 3. The Rice–Wheat Consortium—impact pathways.
Fig. 4. Zero-tillage drill developed in India.
R. Gupta, A. Seth / Crop Protection 26 (2007) 436–447440
giving promising results for development of ‘double no-till’system where both rice and wheat crops are drilled withminimum cultivation. This required development of newseed drill fitted with either a double disk openers ormechanical dibbler- ‘punch planter’, shredders-spreader(Happy Seeder) or roto-coulter type disk-drills. Experi-ments have been undertaken with direct-drilling of rice andwheat crops in both flat and raised bed planting systems(Sayre and Moreno Ramos, 1997; Sayre and Hobbs, 2003).
In the IGP, new resource conserving technologies anddevelopment of appropriate machinery is being combinedwith novel land and water management approaches forgreater efficiency and sustainability of the rice–wheatsystems. At the same time, these technologies are generat-ing alternative sources of productivity growth throughdiversification and intensification of production systems.For example many farmers are now practicing intercrop-ping in raised bed system. In this system wheat is plantedon the raised beds and mint or sugarcane in the furrows.Inter-cropping systems such as maize+ potato/onion/red-beets or sugarcane+ chickpea/Indian-mustard are also
becoming popular with farmers in western Uttar Pradesh,India.
5.2. Water management
The total annual irrigation water requirement of therice–wheat system ranges from 1100 to 1600mm/yr(Chaudhary, 1997). Work initiated in Pakistan in closecollaboration with the private sector, and later supportedby RWC, has successfully adapted the technique of laserland levelling for use in the rice–wheat system. Laserassisted precision land levelling facilitates application ofless water more uniformly under flood irrigation, reducesleaching losses and improves crop-stand and yields. Inrice–wheat system, precision land levelling saves irrigationwater in wheat season by up to 25%; reduces laborrequirements by up to 35%; leads to about 2% increase inthe area irrigated due to removal and/or reduction in sizeof bunds made to impound water for rice cultivation; andincreases crop yields by up to 20% (Gill et al., 2002).Further work is now in progress in all the RWC countriesto integrate other land-preparation and crop-establishmentmethods with laser levelling to reduce water use at the field/farm/basin levels (Rice–Wheat Consortium (RWC), 2004).
5.3. Nutrient management
In the case of nitrogen, findings from IRRI’s research onmatching site-specific capacities of the soil to supplynutrients and to the demand of crop(s) in the system havebeen reflected in the development of a leaf color chart(LCC) to help farmers select the right dose and time ofapplication for optimum response in rice. Efforts have alsobeen made to extend the LCC technology to wheat crop bysynchronising N application with irrigation practices(Shukla et al., 2004; Rice–Wheat Consortium (RWC),2004). The LCC has been widely distributed to tens of
ARTICLE IN PRESSR. Gupta, A. Seth / Crop Protection 26 (2007) 436–447 441
thousand farmers in the consortium countries to assessresponse. LCC technology has the potential to save about15–20% of N fertiliser application in rice (Balasubrama-nian, et al., 2003; Rice–Wheat Consortium (RWC), 2004).The work on other nutrients is less advanced at the farmlevel although a careful examination of long-term experi-ments undertaken in the consortium countries by the RWCis identifying nutrient mining (such as of K) andimbalances, along with the loss of C in some situations,as contributing factors to reduced yields (Ladha et al.,2003). These nutrient management strategies are now beingadapted to new crop and tillage systems in presence ofresidues retained on the soil surface.
5.4. Crop improvement and management
The research on the rice–wheat systems is providinguseful information to the component commodity programsof the International Agricultural Research Centres(IARCs) and the National Agricultural Research Institutes(NARIs). As a result rice breeders have given greaterattention to such traits as early maturity to allow earlierwheat planting to open opportunities for introduction ofshort-season crops, e.g. pulses, potatoes. More recentcommodity research programs in wheat and rice areexamining the genotype� tillage interactions of cultivarsunder zero-till, raised-bed and surface seeding situationsfor their ability to compete with weeds. These develop-ments are also contributing to a broader debate about the
Table 2
Effects on plant emergence and weed density of zero tillage and farmers’
practice for establishment of wheat after rice, Punjab, Pakistan
Tillage methods Plant populationm�2
Wheat Grassy weeds Broadleaf weeds Total
Zero-tillage 114a 59b 54b 113a
Farmers’ practice 96b 72a 90a 162b
Values followed by the same letter do not differ significantly at 5% level.
(Source: Aslam et al., 1993).
Table 3
Effect of tillage practices and sowing time on wheat yield and population of P
Districts Phalaris minor populationm�2 W
Zero-tillage Conventional tillage
timely/delayed sown
Z
Kaithal 121 555 4
Karnal 108 456 4
Sonipat 75 333 3
Panipat 89 440 3
Ambala 73 379 3
Kurukshetra 97 442 4
Source: Mehla et al. (2000).
need for modification of selection criterion in the breedingprograms to accommodate new crop establishment andmanagement practices.As more farmers use the new RCTs, there will be a need
to adapt crop, variety, fertilizer, water and pest manage-ment practices to new systems in relation to local needs.This is already beginning to happen in the management ofthe herbicide resistant weed Phalaris minor. In India P.
minor is an important weed in the wheat crop. Continuoususe of isoproturon for the control of this weed has led todevelopment of severe resistance to this herbicide. Toovercome this problem integrated approaches involvingrotations of crops and other herbicides (e.g. clodinafop,fenoxaprop, sulfosulfuron, tralkoxydim) have been recom-mended. The use of zero-tillage for wheat planting isemerging as a new tool in integrated weed management. Inthe short-term it reduces weed population (Tables 2 and 3)due to elimination of tillage (Aslam et al., 1993; Mehlaet al., 2000) and in conjunction with new herbicidesprovides effective weed control at lower rates, especiallywhen closer row spacing is adopted (Ali and Tunio, 2002;Table 4).
6. Impact of RCTs
6.1. Crop yield
Researchers from both Pakistan and India are report-ing higher wheat yields following adoption of zero-tillagein rice–wheat rotations. In 34 zero-tillage on-farm trialsover 3 years in the rice-growing belt of the PakistanPunjab, higher yields observed with zero-tillage (Table 5).This is largely due to the time saved in land prepara-tion that enabled a more timely planting of wheat crop.It has been reported from the simulation study thatplanting time of wheat regulates yield, governed by theclimatic parameters, mainly through temperature anddelayed planting results in significant losses in yield (Raiet al., 2004).Although a statistical treatment to data from Haryana,
India, included in Table 6 was not possible, zero-tillageplots again gave higher yields compared to conventional
halaris minor
heat yield kg/ha
ero-tillage Conventional tillage
timely sown
Conventional tillage
delayed sown
652 4217 3935
503 4200 3869
489 3270 2059
800 4000 3583
825 3638 2997
593 4383 4016
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Table 4
Effect of various planting geometry on weed control in wheat and grain
yield
Treatments Weeds
before
application
Weeds after
application
Decrease/
increase
weeds (%)
Yield
(kg/ha)
Close row sowing 71 77 8.5 2699
Close row
sowing+Buctril-
M at 1.0 l/ha
65 28 �48.6 3457
Cross row sowing 71 77 7.7 3063
Cross row
sowing+ Buctril-
M at 1.0 l/ha
72 26 �64.3 3821
Skip row sowing 71 81 13.4 2487
Skip row
sowing+Buctril-
M at 1.0 l/ha
74 25 �67.0 3184
Weedy check for
full season
81 96 — 2365
Source: Ali and Tunio (2002).
Table 5
Grain yield of wheat in zero-tillage and farmers’ practice after puddled
transplanted rice in Pakistan and India
Year Country No. of
farmers
involved
Grain yield (kg/ha)
Zero-
tillage
Farmers’
practicea
1985–1988 Punjab, Pakistan 34 3890a 3528b
2001–2004 Western Uttar
Pradesh, India
27 5120 4980
1999–2000 Haryana, India 124 5380 5110
2000–2003 Eastern UP and
Bihar
357 3350 2980
Source: RWC (2004) and Aslam et al. (1993) for data from India and
Pakistan, respectively.
Means between zero-tillage and farmers’ practice followed by the same
letter do not differ significantly at Po0.05 using DMRT. Statistical
analysis of the field data from India not done.aWheat crop was established after 5–8 tractor-passes for tillage
operations.
Table 6
Effects of bed size configuration on wheat yield (kg/ha), Punjab
Agricultural University, Ludhiana, India, 1994�1995
Variety Sowing methods
On the flat 75-cm wide beds 90-cm wide beds Mean
25-cm row 2 rows 2+1 rowsa 3 rows 3+1 rowsb
PBW 226 5740 6170 6390 6160 6320 6160a
WH 542 6290 5830 6360 6000 6040 6110a
CPAN 3004 6020 5530 6140 5630 5600 5780b
PBW 154 5460 5110 6000 5930 5880 5680b
HD 2329 5770 4660 6190 5580 5810 5600b
PBW 34 5650 5610 5800 5580 5630 5650b
Mean 5820b 5490c 6150a 5810b 5880b —
Source: Dhillon et al. (2000a, b).
Means of varieties and sowing method followed by the same letter do not
differ significantly at Po0.05 using DMRT.a2+1 mean that an extra row of wheat was planted at the bottom of the
furrow.b3+1 mean that an extra row of wheat was planted at the bottom of the
furrow.
R. Gupta, A. Seth / Crop Protection 26 (2007) 436–447442
tillage (based either on farmer survey or crop-cuttingexperiments in farmers’ fields), which over districts andsowing time averaged at around 270 kg/ha (wheat yieldof 5380 and 5110 kg/ha for zero till and conventionaltillage, respectively). Results of studies conducted byMehla et al. (2000) on 132 farmers’ fields in Haryana werein general conformity with the results presented in Table 6.In eastern Gangetic Plains, where late planting of wheat isquite common, yield losses can be much higher due toshorter winter season window for wheat growth. In thissituation productivity gains due to advancement in wheatplanting through adoption of zero-tillage, as widelyobserved in RWC managed trials, can be in the range of
400–1000 kg/ha. Research has shown that the zero-tillsystem advances crop planting by at least 1 week therebyreducing yield losses by 1–1.5%/day after optimum wheat-sowing time (Hobbs and Gupta, 2003, 2004; Aslam et al.,1993; Ortiz Monasterio et al., 1994; Mehla et al., 2000).In an on-station trial in Punjab, India, considerablevariations in the performance between cultivars of wheatwas observed under flat and raised bed systems andplanting densities, highlighting the need for additionalresearch in breeding and development of cultivars appro-priate for the raised bed planting system (Dhillon et al.,2000a, b). It should be noted, however, that under fieldsituation raised-bed and furrow dimension is usuallygoverned by the width of the tractor. Consortium partnershave observed that two beds formed per tractor pass(134 cm wide, Indian tractors), restricts soil compactionto tractor lanes and facilitates formation of a perma-nent raised bed planting system (Rice–Wheat Consor-tium (RWC), 2004). The timing of the first irrigationfor wheat on beds may need to be earlier than therecommended practice for wheat on flat layouts on thecoarse textured soils of north-west India (Prashar et al.,2004).
6.2. Cost comparison under reduced tillage systems with
conventional practices
Net benefits in India and Pakistan average aroundUS$ 150 ha�1. Contributory factors to cost savingsincluded: higher yields and reduced cost of cultivation(about half of that for the conventional tillage system).More information on cost comparison of zero-tillageover conventional cultivation based on a survey offarmers’ perceptions and research findings is summarizedin Table 7.
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Table 7
Benefits of zero-tillage over conventional tillage for planting of wheat after rice in Haryana, India
Item Farmers’ perceptions Researchers’ findings
Sowing Wheat sowing earlier by 5�8 days (small-to-medium farms) to 2
weeks (large farms)
On average, wheat sowing can be advanced by 5�15
days
Fuel savings Not available On average 60 l diesel per ha
Cost of cultivation US$ 42�92 ha�1 US$ 37�62 ha�1
Plant population 20�30% more plants in zero-tillage fields 13.5% more plants in zero-tillage fields
Weed infestation 20% less and weaker weeds in zero-tillage fields 43% less weeds in zero-tillage fields
Irrigation Saves 30�50% water in the first irrigation and 15�20% in
subsequent irrigations
36% less water used, on average
Rice stem borer
infestation
Less, because of less stubble sprouting Winter coolness impairs sprouting and thus borer
development. Beneficial insects in stubble help control
borers
Rice stubble Decayed faster Decayed faster
Fertilizer-use efficiency High Higher because of placement
Wheat yields Higher than under conventional system depending on days
planted earlier
420�530 kg more per ha
Source: Hobbs and Gupta (2002).
R. Gupta, A. Seth / Crop Protection 26 (2007) 436–447 443
6.3. Impact on the environment
Straw retained on the soil surface reduces weed seedgermination and growth, moderates soil temperature andreduces loss of water through evaporation. In addition,crop residue is also an important source of fodder foranimals in the IGP countries. Despite these potentialbenefits, however, large quantities of straw (left over afterrice and wheat harvesting) are burnt each year by farmersto facilitate land preparation for crop planting. It isestimated that the burning of one ton of straw releases 3 kgparticulate matter, 60 kg CO, 1460 kg CO2, 199 kg ash and2 kg SO2. With the development of new drills, which areable to cut through crop residue, for zero-tillage cropplanting, burning of straw can be avoided, which amountsto as much as 10 tons per hectare, potentially reducingrelease of some 13–14 tons of carbon dioxide (Gupta et al.,2004). Elimination of burning on just 5 million hectareswould reduce the huge flux of yearly CO2 emissions by 43.3million tons (including 0.8 million ton CO2 produced uponburning of fossil fuel in tillage). Zero-tillage on an averagesaves about 60 l of fuel per hectare thus reducing emissionof CO2 by 156 kg per hectare per year (Grace et al., 2003;Gupta et al., 2004).
Adoption of RCTs which allow alterations in water,tillage and surface residue management practices can havea direct effect on emissions of greenhouse gases (GHGs)and enhance the carbon stocks of the soil. Soil submer-gence in rice cultivation leads to unique processes thatinfluence ecosystem sustainability and environmentalservices such as carbon storage, nutrient cycling and waterquality. For example the submergence of soils promotesthe production of methane by anaerobic decomposition oforganic matter. However, worries that such rice systemsare a major contributor to global warming were allayedthrough a wide-scale study in the region (Wassman et al.,2001). It has been noticed that methane emissions from rice
fields range from 16.2 to 45.4 kg/ha during the entireseason, whereas nitrous oxide emission under rice andwheat crops amounts to 0.8 and 0.7 kg/ha, respectively(Pathak et al., 2002). Incorporation of straw increasesmethane emissions under flooded conditions, but surfacemanagement of the straw under aerated conditions andtemporary aeration of the soils can mitigate these effects.Thus, adoption of aerobic mulch management withreduced tillage is likely to reduce methane emissions fromthe system.The water regime can strongly affect the emission of
nitrous oxide, another GHG, which increases undersubmergence, and is negligible under aeration. Anyagronomic activity that increased nitrous oxide emissionby 1 kg/ha needs to be offset by sequestering 275 kg/ha ofcarbon, or reducing methane production by 62 kg/ha.Adoption of RCTs would favour the decrease of thisGHG.In order to minimize nitrate pollution of ground water,
volatilization losses of fertilizer N in rice/wheat, andaddress issues of crop residue burning, receding watertable and emission of GHG, measures such as introductionof a legume crop (Mungbean) between wheat and rice, deepplacement of nitrogenous fertilisers and raised bed plantingand laser land levelling have been developed. With furtherrefinement of double disk planters, punch planter and roto-disk-drill it has become easier to plant crops with throughretained residues. These implements are now beingevaluated in farmer participatory trials along with modifiedfertilizer and irrigation practices (Rice–Wheat Consortium(RWC), 2004, 2005).Given the potential of RCTs to influence all the major
GHGs, and underground water reserves and its quality, inplanning future research it is important that due con-sideration is given to potential positive and negativeimpacts of agronomic and crop management practices onthe environmental quality.
ARTICLE IN PRESSR. Gupta, A. Seth / Crop Protection 26 (2007) 436–447444
6.4. Extent of uptake of RCTs
Over the last 5 years, farmers have rapidly adopted zero-tillage for planting of wheat and other crops after rice. Ithas been estimated that close to 2mha have been coveredwith zero-till planting of winter season crops (wheat,maize, lentil, chickpea, peas, etc.) in year 2004, mainly inIndia and Pakistan. The acreage of zero-till/reduced-tillwinter season crops was nearly 1.7mha during the sameperiod in Indian part of the IGP. The area of wheat plantedto zero-till in 2002 and 2003 were estimated to be 0.37 and1.1mha respectively. Fig. 5 shows the emerging trends inSouth Asia (India, Pakistan, Nepal and Bangladesh). Thespread of RCTs has also encouraged the growth of privatesector input providers. It is estimated that in 2004 nearly100 small private entrepreneurs were manufacturing directdrills in India and 50 in Pakistan. In the year 2000 thisnumber was just 5 in the two countries (RWC, 2005). Asurvey shows that even resource-poor smallholders havestarted to benefit from this technology by using contractorsto direct-drill their crops. Some more progressive farmersare now experimenting with the option of establishing riceeither as a transplanted or a direct dry seeded crop inunpuddled no-till fields with a view to ‘double no-till’rice–wheat-planting system.
7. Conclusions and future directions
The natural resource management issues impacting onsustainability of the rice–wheat systems are complex anddiffer significantly between different parts of IGP transects.Locally adapted RCTs appropriate to resource endow-ments of farmers and the biophysical environment holdpotential to improve management of natural resources andprovide sustainable increases in productivity.
The increasing demand for basic cereals in the futurewould need to be met largely through increased productiv-ity, allowing some land (and other resources) for diversi-fication for greater income generation. Clearly, marketforces and national and state policies will drive the paceand form of the diversification. An additional factorinfluencing the diversification of RWSs would be the new‘platform’ made possible by the RCTs.
2 5 20 130
371
1100
2100
0
500
1000
1500
2000
1998-99 1999-00 2000-01 2001-02 2002-03 2003-04 2004-05
Are
a (,
000
ha)
Fig. 5. Increase in area under zero-till winter season crops including wheat
planted after rice in South Asia (Source: RWC, 2004).
Socio-economic and biological research to determine thefeasibility of changing the culture of rice to enhanceproductivity, diversity and sustainability, particularlyregarding water use, are needed to determine under whatcircumstances such changes are appropriate.Changes in tillage as well as land and water management
practice, and a better understanding of drivers of thediversification process may require adjustments in all of thecomponent technology for the new systems. This willinvolve examination of such issues as to which rice-basedecology to diversify, in which season and how best toaddress the multidimensional nature of poverty, includingconsideration of issues related to risk management,improved livelihoods, food security and nutrition.The long-term trials, set up at the beginning of the green
revolution era to understand nutrient mining in the systemand to develop nutrient management strategies haveprovided valuable information to develop future strategies.Appropriate long-term monitoring must continue, and berelevant to future changes in tillage and water managementpractices. In addition, benefits of changes in the tillagesystem and stubble management to the soil ecosystem needto be better understood.The main contribution in IPM research so far has been
in the control of P. minor. However, the new tillage systemswith reliance on herbicide inputs are likely to change theweed species and expose the system to more herbicideresistance. Gaps remain in the IPM agenda for the systemsof today and there is a need for anticipatory IPM research(e.g., integrated weed, insect and disease management, theemerging role of nematodes in a more diversified andaerated system) in the context of the new RCT systems.The changes in the RWSs have the potential to change
the balance in global warming gases. Reduced tillageincreases carbon accumulation in the soil and reduces fuel-based emissions. Soil submergence is the dominant featureof present rice cultivation in the IGP and leads to uniquebiogeochemical processes that influence methane andnitrogen gas emissions and nutrient availability. Changesin rice culture to a more aerated system could change thebalance of these gases for the better.
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