Intercropping, the simultaneous production of multiple crops on the same field, has been widely practiced by smallholder farmers in developing countries and is gaining increasing interest in developed countries. The most obvious advantage of intercropping is land sparing. However, there is a lack of synthesis of global data on the absolute yield gain of intercropping, measured as the difference between the observed yield of intercrops and the expected yield based on sole crops.
Various crop species combinations have been utilized around the world. Crop species can be grown simultaneously or partly so, and in no distinct row arrangement (mixed) or in alternate rows or strips on the same field. We asked how species combination, temporal and spatial arrangement, and fertilizer input affect the yield gain of intercropping. To answer this question, we performed a global meta-analysis on yield gain for grain production in annual intercrops.
Results/Conclusions
We found a previously undescribed dichotomy in intercropping systems that could be regarded as two syndromes of production. These different strategies have likely been developed to address different production objectives. On the one hand, systems with maize, commonly used in China, represent a strategy of intercropping based on high inputs, high outputs, and a comparatively large intercropping advantage in terms of absolute yields per hectare. These systems are based on strip intercropping with narrow strips (usually in the order of 1-2 m wide), and a relay sequence in the sowing and harvesting of the intercropped species. On the other hand, systems without maize were often cultivated with low inputs, and had substantially lower intercropping benefits in terms of absolute yield per hectare. These intercropping systems were usually grown as simultaneous intercrops, with simultaneous sowing and harvesting of the two species, and with the species grown most often in alternate rows or completely mixed, but not often in strips. This type of system addresses the aim of developing an agricultural system that exploits species complementarities to drastically lower inputs, but these systems had lower outputs than the systems of the first syndrome.
Both the low and high yield intercropping strategies saved 16-29% land and 19-36% fertilizer compared to monocultures grown with the same management. The advantages of the two syndromes of production in intercropping uncovered by this meta-analysis confirm that intercropping increases outputs and saves fertilizers in both low and high input systems.