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Cuernavaca, Mexico

Reynolds T.W.,Colby College | Waddington S.R.,Apartado Postal 4 205 | Anderson C.L.,University of Washington | Chew A.,University of Washington | And 2 more authors.
Food Security | Year: 2015

Many environmental factors constrain the production of major food crops in Sub-Saharan Africa and South Asia. At the same time, these food production systems themselves have a range of negative impacts on the environment. In this paper we review the published literature and assess the depth of recent research (since 2000) on crop x environment interactions for rice, maize, sorghum/millets, sweetpotato/yam and cassava in these two regions. We summarize current understandings of the environmental impacts of crop production systems prior to crop production, during production and post-production, and emphasize how those initial environmental impacts become new and more severe environmental constraints to crop yields. Pre-production environmental interactions relate to agricultural expansion or intensification, and include soil degradation and erosion, the loss of wild biodiversity, loss of food crop genetic diversity and climate change. Those during crop production include soil nutrient depletion, water depletion, soil and water contamination, and pest resistance/outbreaks and the emergence of new pests and diseases. Post-harvest environmental interactions relate to the effects of crop residue disposal, as well as crop storage and processing. We find the depth of recent publications on environmental impacts is very uneven across crops and regions. Most information is available for rice in South Asia and maize in Sub-Saharan Africa where these crops are widely grown and have large environmental impacts, often relating to soil nutrient and water management. Relatively few new studies have been reported for sorghum/millets, sweetpotato/yam or cassava, despite their importance for food security on large areas of marginal farmland in Sub-Saharan Africa – however, there is mounting evidence that even these low-input crops, once thought to be environmentally benign, are contributing to cycles of environmental degradation that threaten current and future food production. A concluding overview of the emerging range of published good practices for smallholder farmers highlights many opportunities to better manage crop x environment interactions and reduce environmental impacts from these crops in developing countries. © 2015, The Author(s). Source

Li X.,Huazhong Agricultural University | Liu N.,Huazhong Agricultural University | You L.,Huazhong Agricultural University | You L.,International Food Policy Research Institute | And 4 more authors.
PLoS ONE | Year: 2016

After a remarkable 86% increase in cereal production from 1980 to 2005, recent crop yield growth in China has been slow. County level crop production data between 1980 and 2010 from eastern and middle China were used to analyze spatial and temporal patterns of rice, wheat and maize yield in five major farming systems that include around 90% of China's cereal production. Site-specific yield trends were assessed in areas where those crops have experienced increasing yield or where yields have stagnated or declined. We find that rice yields have continued to increase on over 12.3 million hectares (m. ha) or 41.8% of the rice area in China between 1980 and 2010. However, yields stagnated on 50% of the rice area (around 14.7 m. ha) over this time period. Wheat yields increased on 13.8 m. ha (58.2% of the total harvest area), but stagnated on around 3.8 m. ha (15.8% of the harvest area). Yields increased on a smaller proportion of the maize area (17.7% of harvest area, 5.3 m. ha), while yields have stagnated on over 54% (16.3 m. ha). Many parts of the lowland rice and upland intensive sub-tropical farming systems were more prone to stagnation with rice, the upland intensive sub-tropical system with wheat, and maize in the temperate mixed system. Large areas where wheat yield continues to rise were found in the lowland rice and temperate mixed systems. Land and water constraints, climate variability, and other environmental limitations undermine increased crop yield and agricultural productivity in these systems and threaten future food security. Technology and policy innovations must be implemented to promote crop yields and the sustainable use of agricultural resources to maintain food security in China. In many production regions it is possible to better match the crop with input resources to raise crop yields and benefits. Investments may be especially useful to intensify production in areas where yields continue to improve. For example, increased support to maize production in southern China, where yields are still rising, seems justified. © 2016 Li et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Kamanga B.C.G.,Wageningen University | Waddington S.R.,Apartado Postal 4 205 | Waddington S.R.,University of Livingstonia | Whitbread A.M.,University of Gottingen | And 2 more authors.
Experimental Agriculture | Year: 2014

Mineral fertiliser is a scarce input for smallholder maize farmers in Malawi. A recent provision of small amounts of subsidised fertilisers by government programmes to farmers throughout Malawi has increased fertiliser access and raised maize production, but fertiliser management and yield responses frequently remain poor. To seek ways to use the fertiliser more efficiently, we analysed the effects of low rates of N (15 or 30 kg N ha-1) and P (9 kg P ha-1) fertiliser in combination with improved weed management on maize yields in experiments on 12 smallholder farms in Chisepo, central Malawi. Several indices of N and P use efficiency were computed from the above-ground crop components and nutrient contents. Maize yield simulations were conducted using long-term rainfall records in the APSIM crop-soil system model. NP fertiliser significantly (p < 0.001) raised maize grain yield from 0.65 to 1.5 t ha-1, and twice-weeding fertilised maize significantly (p < 0.001) raised maize yields by 0.4 t ha-1 compared with weeding once (0.9 t ha-1). The agronomic efficiency of applied fertiliser N (AEN) averaged 19.3 kg grain kg N-1 with one weeding but doubled to 38.7 kg with the additional weeding. The physiological efficiency of applied N (PEN) was 40.7 kg grain kg-1 N uptake. APSIM predicted that similar or larger maize yield responses to 15 or 30 kg N ha-1 can be expected in 8 out of 10 years in areas with similar rainfall patterns to Chisepo. A financial analysis showed that the application of these small amounts of fertiliser was economic even when fertiliser was purchased from the open market, provided the crop was adequately weeded. Participatory assessments helped farmers understand the increased efficiency of fertiliser use possible with additional weeding, although some farmers reported difficulty implementing this recommendation due to competing demands for labour. We conclude that to raise the productivity and sustainability of fertiliser support programmes in Malawi, initiatives should be introduced to help identify and educate farmers on the major drivers of productivity in their systems. Copyright © Cambridge University Press 2013. Source

Liu N.,Huazhong Agricultural University | Li X.,Huazhong Agricultural University | Waddington S.R.,Apartado Postal 4 205
Food Security | Year: 2014

The growth of food production from an intensification of cereal-based cropping systems in India and China has received great attention by domestic and international research in recent years. Heavy use of fertilizers on fertile soils has been a crucial factor in the increased crop production, contributing greatly to food security, but there is rising concern about the sustainability of such practices in those countries. Based on an extensive survey of 246 key informants, this paper assessed yield losses of rice and wheat associated with soil (physical and fertility) constraints and fertilizer constraints in three major cereal-based farming systems on the Indian sub-continent (India, Bangladesh and Nepal) and three in China where cereal yields and production have risen substantially in past decades. For rice, respondents considered soil constraints to be important causes of lower yields, contributing about 6 % of their estimated yield gap (where the yield gap is made up from the losses associated with a wide range of constraints to crop production) for each of the three Chinese farming systems and 7.8–14.6 % of the yield gap for the systems on the Indian sub-continent. Fertilizer constraints were also important for rice in some of these intensive farming systems, and were associated with 10.5 % of the yield gap in the Indian Rice wheat system. For wheat, the highest yield reductions were reported in the Chinese systems, with losses of 9.7–17.5 % from soil and fertilizer constraints combined. Overall, soil constraints (such as the depletion of soil fertility and N deficiency) usually accounted for larger yield reductions with rice while fertilizer constraints (including insufficient use of N fertilizer, high cost or short supply of N fertilizer, poor management of fertilizer and inappropriate use of other (non-N) fertilizers) were considered more severe for wheat. This study underlined the importance of soil and fertilizer constraints for rice and wheat in major Indian and Chinese cereal-based farming systems, alongside other important constraints such as drought for rice and late planting and poor crop rotations for wheat. Respondents proposed numerous interventions to address the constraints, with systematic soil fertility testing programs, appropriate government subsidies for fertilizer, and better management of fertilizer nutrients being among the most popular. Integrated measures, customized for the different systems, and involving combinations of improved crop management and inputs, better varieties and appropriate policy or socioeconomic support, need to be taken step-by-step, to increase land productivity and improve the efficiency of fertilizer use in these intensive cereal farming systems that are vital for global food security. © 2014, Springer Science+Business Media Dordrecht and International Society for Plant Pathology. Source

Kamanga B.C.G.,Wageningen University | Kanyama-Phiri G.Y.,University of Malawi | Waddington S.R.,Apartado Postal 4 205 | Almekinders C.J.M.,Wageningen University | Giller K.E.,Wageningen University
Food Security | Year: 2014

We studied the process of assessment and adoption of 10 grain- and green-manure legumes by smallholder maize farmers differing in resource endowment in Chisepo, central Malawi. The legumes had been promoted with the farmers from 1998 to 2004, primarily as a way to diversify food production and maintain the fertility of their soils. Farmers (n = 136) were surveyed in 2004 at the end of the period of promotion to assess the degree of awareness and uptake of the legumes and the reasons for adoption. A follow-up survey was conducted in 2007 among a broader sample of Chisepo farmers (n = 84) to measure the persistence of adoption. An Analytic Hierarchy Process (AHP) was used in 2004 to create scales of priority and as a tool to compare predicted with actual legume uptake. Actual adoption of food grain legumes reflected predictions by the AHP but it over-predicted uptake of the non-food legumes. The AHP helped us understand how farmer perceptions and needs influence adoption, as well as limitations with the legumes. Suitability for food was the most important criterion that farmers identified for adoption, followed by contribution to soil fertility and suppression of weeds. Over 75 % of the farmers surveyed in 2004 were aware of most of the legumes. Frequent use of the grain legumes was reported in 2004 (79 % for CG7 groundnut, 77 % for soyabean and 47 % for pigeonpea) by both the better-resourced (wealthier) and less-well-resourced (poorer) farm households. Awareness rose to over 90 % of farmers surveyed in 2007 but adoption fell somewhat to 67 % for soyabean, 57 % for CG7 groundnut and 43 % with pigeonpea among the wealthier farmers, while Bambara groundnut rose to 38 %. Fifty-two percent of poorer farmers reported adoption of CG7, 46 % soyabean, 35 % Bambara groundnut and 27 % pigeonpea in 2007. There was greater uptake by the wealthier farmers than those with fewer resources. Overall, although the legumes were promoted for maintenance of soil fertility, farmers were largely interested in and mainly adopted those legumes they considered most useful for food diversity and security, and with potential for market sale. Only a few wealthier farmers used mucuna and tephrosia among the green manure legumes. Improving the food value of vigorous and productive multi-purpose legumes, particularly mucuna, may help raise the farmers' interest, with secondary benefits for soil fertility. © 2014 Springer Science+Business Media Dordrecht and International Society for Plant Pathology. Source

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