Sustainably feeding the world's growing population is a challenge, and closing yield gaps (that is, differences between farmers' yields and what are attainable for a given region) is a vital strategy to address this challenge. The magnitude of yield gaps is particularly large in developing countries where smallholder farming dominates the agricultural landscape. Many factors and constraints interact to limit yields, and progress in problem-solving to bring about changes at the ground level is rare. Here we present an innovative approach for enabling smallholders to achieve yield and economic gains sustainably via the Science and Technology Backyard (STB) platform. STB involves agricultural scientists living in villages among farmers, advancing participatory innovation and technology transfer, and garnering public and private support. We identified multifaceted yield-limiting factors involving agronomic, infrastructural, and socioeconomic conditions. When these limitations and farmers' concerns were addressed, the farmers adopted recommended management practices, thereby improving production outcomes. In one region in China, the five-year average yield increased from 67.9% of the attainable level to 97.0% among 71 leading farmers, and from 62.8% to 79.6% countywide (93,074 households); this was accompanied by resource and economic benefits.
Double cropping of wheat and maize is common on the North China Plain, but it provides limited income to rural households due to the small farm sizes in the region. Local farmers in Quzhou County have therefore innovated their production system by integration of watermelon as a companion cash crop into the system. We examine the economic performance and sustainability of this novel intercropping system using crop yield data from 2010 to 2012 and farm household survey data collected in 2012. Our results show that the gross margin of the intercropping system exceeded that of the double cropping system by more than 50% in 2012. Labor use in the intercropping system was more than three times that in double cropping. The lower returns per labor hour in intercropping, however, exceeded the average off-farm wage in the region by a significant margin. Nutrient surpluses and irrigation water use are significant larger under the intercropping system. We conclude that the novel wheat-maize/watermelon intercropping system contributes to rural poverty alleviation and household-level food security, by raising farm incomes and generating more employment, but needs further improvement to enhance its sustainability.
Intercropping is a promising model for ecological intensification of modern agriculture. Little information is available on how species growth patterns are affected by size-asymmetric above-and belowground competitive interactions, especially in intercrops with more than two species. We studied plant growth and competitive interactions in a novel intercropping system with three species: wheat, watermelon and maize. Wheat and maize are grown sequentially (as a double cropping system) in narrow strips while watermelon is grown between the cereal strips, with partial overlap in growing period with the two cereals. Growth patterns were monitored over two years and described with logistic growth curves. Root barriers were used to study the effect of belowground interactions. Wheat produced 31% greater yield per plant in the intercrop than in the sole crop but 24% lower yield per unit total (inter)crop area. Wheat yield increase per plant was associated with faster growth and substantial overyielding in the outer rows of wheat strips. Watermelon did not competitively affect wheat. Watermelon biomass was substantially reduced at the time of wheat harvest. However, compensatory growth after wheat harvest and greater allocation to fruits resulted in a good yield of intercropped watermelon, 92% of monoculture yields, at final harvest. Intercropped maize produced 32% lower grain yield per plant and per unit area than sole maize, as a consequence of later sowing and a changed plant configuration in the intercrop as compared to the sole crop, and competitive effects of watermelon, as shown by comparison with a skip-row maize system without watermelon. Root barriers did not affect yield of any of the species, indicating that aboveground competitive interactions in this case played a more important role in shaping the observed growth responses than belowground interactions. Plant interactions in this tripartite intercrop system are consistent with the hypothesis of size-asymmetric competition for light.
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