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In Molden, David (Ed.). Water for food, water for life: a Comprehensive Assessment of Water Management in Agriculture. London, UK: Earthscan; Colombo, Sri Lanka: International Water Management Institute (IWMI).

Although conceptually simple and often idealized, disentangling crop–livestock interactions typically proves more complex in practice. Part of the complexity arises from their changing nature along agricultural intensification gradients. Such interactions increase in scope when extensive systems intensify, but decline in importance as already intermediate systems intensify further. This changing nature of crop–livestock interactions in relation to the system’s developmental stage implies that these exchanges can both contribute but also undermine system sustainability. We examine crop–livestock interactions in the Indo-Gangetic Plains as an empirical case, drawing from village surveys to explore and illustrate these relations and implications along the agro-ecological gradient of this vast and important eco-region. Such an understanding is increasingly needed as adapting crop residue management practices is recognized as the key to address sustainability concerns in the prevailing rice–wheat systems and as a stepping stone towards conservation agriculture. The agricultural R&D community needs to incorporate this understanding more proactively into its R&D agenda if it is to succeed in sustaining productivity gains, improving rural livelihoods equitably, and securing environmental sustainability.

world’s population, making these systems critically important for global food security (Timisina and Connor, 2001; Ladha et al., 2003b). In South Asia rice–wheat systems produce more than 30% of the rice and 42% of the wheat consumed (RWC-CIMMYT, 2003: 24) and cover about 14 million ha of cultivated land – with most of the area located in India and the Indo-Gangetic Plains (IGP) (Timisina and Connor, 2001). Recent studies indicate a slowdown in productivity growth in the rice–wheat systems of India (Kumar et al., 2002). Evidence from longterm experiments shows that crop yields are stagnating and sometimes declining (Duxbury et al., 2000; Ladha et al., 2003a). Current crop cultivation practices in rice–wheat systems degrade soil and water resources and thereby threaten the sustainability of the system (Byerlee and Siddiq, 1994; Fujisaka et al., 1994; Hobbs and Morris, 1996; Ali and Byerlee, 2000; Duxbury et al., 1994; Kumar and Yadav, 2001; Gupta et al., 2003; Ladha et al., 2003a). The prevailing policy environment has encouraged inappropriate land and input use (Pingali and Shah, 1999) and crop system constraints have encouraged unsuitable responses. If the supply of food is to keep pace with rapidly growing demand, rice–wheat farmers will have to produce more food from fewer resources while sustaining environmental quality. This will require rapid technological change towards technologies that are both more productive and less resource-degrading. The Rice–Wheat Consortium of the IndoGangetic Plains (RWC; www.rwc.cgiar.org) is a consortium involving international agricultural research centres and national agricultural

A conservative ex-ante assessment of supply-shift gains alone (excluding social and environmental gains), shows that the investment in zero tillage (ZT) R&D by the Rice-Wheat Consortium and CIMMYT was highly beneficial with a benefit-cost ratio of 39, a net present value of US$ 94 million and an internal rate of return 57%. Sensitivity analysis highlights the influential role of the yield gain, the contribution of reduced tillage (i.e. partial adoption) and the assumed time-lag. Significant positive spillovers of sunk ZT R&D costs both previous and from elsewhere - also contributed to the high returns. The case thereby highlights the potential gains from successful technology transfer and adaptation. The case however also underscores that international NRM research can have a high return, particularly when it has wide applicability.

Crop residue mulching (CRM) can be defined as a technology whereby at the time of crop emergence at least 30% of the soil surface is covered by organic residue of the previous crop. The present study proposes CRM as the most adequate term for the technology in view of the substantial controversy and confusion surrounding existing terms, particularly conservation tillage. CRM is a dual-purpose technology that combines conservation and productivity effects. Its conservation potential hinges on the presence of the crop residues as mulch. This mulch provides a protective layer to the soil surface that is extremely effective in halting soil erosion and also amends the soil ecology. Its productivity potential is twofold. First, the mulch tends to stabilise, and occasionally even enhance, crop yield. Second, it implies factor substitution and input use efficiency alterations. The paper presents the residue balance as an analytical tool to assess the current availability of residues—both in terms of current residue production and current residue destinations. Residue destinations typically include extraction, burning in situ, incorporation, weathering and retention as mulch. CRM has profound implications for crop management. First, CRM implies a set of necessary practices so as to ensure the retention of sufficient residues as mulch. Second, CRM may imply complementary adaptations in order to be able to grow a crop and/or maintain productivity levels. Therefore, CRM is not a simple add-on technology, but instead a complete package of cultural practices. The actual potential of the CRM technology depends on a comprehensive assessment of the socio-economic implications of the implied changes. This potential is site-specific and will diverge between the private and social viewpoint. CRM therefore is a promising dual-purpose technology—but no panacea for soil conservation in (semi-)tropical countries.

Mixed crop–livestock farming systems prevail in Mexico – typically rain-fed and smallholder systems based on maize and ruminants and spanning diverse agro-ecologies. Maize grain is the key Mexican staple produced for home consumption and the market. Maize crop residues (stover) are an important by-product, primarily for feed use, often through in situ stubble grazing and/or as ex situ forage. This paper explores maize stover use along the agro-ecological gradient and the potential trade-offs, particularly the widespread use of maize stover as feed against its potential use as mulch (soil cover) to manage soil health within the context of conservation agriculture. The paper builds on three case study areas in Mexico in contrasting agro-ecologies: (semi-)arid, temperate highland and tropical sub-humid. Data were obtained through expert consultation and semi-structured farmer group/community surveys. Although in situ grazing is found in all three study sites, it represented the bulk of stover use in only one site (70% of stover in the sub-humid tropics), with ex situ feed dominating in the other two sites (>80%). Maize stover commercialization is limited and mainly restricted to households with no livestock and often within the local context. Farmers are generally hesitant to adopt conservation agricultural practices that require the retention of stover as mulch, as this competes with their livestock feed needs and purchased feed is expensive. To reduce trade-offs, a portfolio of options could be adapted to these mixed systems, including partial residue retention, cover and feed crops and sustainable intensification. Promising but yet to be explored, are investments in the genetic improvement of maize stover feed quality.

Creating interest and excitement around new research findings has become an important part of the research funding cycle. NERICA (New Rice for Africa) is a rice type developed by the Africa Rice Center (WARDA). Since the emergence of NERICA varieties at the turn of the millennium, claims about their characteristics and potential have been made by WARDA and repeated by many of WARDA's funders, other development organizations and the media. This has led to large-scale support for these varieties, international accolades and continued funding. In this paper, the authors review the evidence that is in the public domain in relation to claims in three specific areas: yield potential, weed competitiveness and impacts in Guinea. It is concluded that the main claims about NERICA are not well supported, and that this has implications not only for WARDA but for the funding of agricultural research more broadly.

This paper reviews recent advances in, and challenges for, weather index insurance for managing drought risk in smallholder agriculture, with a focus on sub-Saharan Africa. Despite its promise to integrate local agricultural risk smoothing with insurance principles, there remain many challenges to its mainstreaming in low income countries. Scaling up of weather index insurance pilot projects is particularly constrained by high-basis risk, related to the divergence between the calculated weather index and actual productivity loss on the farm. Various options may be considered to enhance uptake of weather index insurance. Linking reliable weather data with location-specific crop and agronomic conditions using flexible geospatial crop modeling tools is one option to reduce the basis risk. The other option is interlinking weather index insurance with credit or safety nets. In the end, insurance should be offered as part of a wider set of business services that provide real value to smallholders. Finally, the review acknowledges that the suggested conceptual solutions, especially interlinking index based weather insurance with credit will require more empirical evidence on the extent to which insurance would reduce the cost of borrowing and make credit more accessible to the smallholder farmers.

Zero tillage planting of wheat after rice has been the main success in the quest for resource-conserving technologies that can save water, reduce production costs and improve production in the Indo–Gangetic Plains, the cereal bowl of South Asia. Binomial logit models are used to assess the structural factors associated with its adoption in the rice–wheat systems of India's Haryana state and Pakistan's Punjab province. Zero tillage adoption is closely associated with a more favourable resource base and rice–wheat specialization in both study areas. This calls for a closer consideration of equity implications in future research and development.