Influence of spatial arrangement, biofertilizers and bioirrigation on the performance of legume – millet intercropping system in rainfed areas of southern India

In this study, we checked the potential of bioirrigation - defined as a process of hydraulic lift where transfer of water occurs from deep soil layers to top soil layers through plant roots. We tested this in a pigeon pea (PP) - finger millet (FM) intercropping system in a field study for two consecutive growing seasons (2016/17 and 2017/18) at two contrasting sites in Bengaluru and Kolli Hills, India. Our objective was also to optimize the spatial arrangement of the intercropped plants (2 PP:8 FM), using either a row-wise or a mosaic design. The field trial results clearly showed that spatial arrangement of component plants affected the yield in an intercropping system. The row-wise intercropping was more effective than mosaic treatments at the Bengaluru field site, while at Kolli Hills, both row-wise and mosaic treatment performed equally. Importantly, biofertilizer application enhanced the yield of intercropping and monoculture treatments. This effect was not influenced by the spatial arrangement of component plants and by the location of the field experiment. The yield advantage in intercropping was mainly due to the release of PP from interspecific competition. Despite a yield increase in intercropping treatments, we did not see a positive effect of intercropping or biofertilizer on water relations of FM, this further explains why PP dominated the competitive interaction, which resulted in yield advantage in intercropping. FM in intercropping had significantly lower leaf water potentials than in monoculture, likely due to strong interspecific competition for soil moisture in intercropping treatments. Our study indicates that identity plant species and spatial arrangement/density of neighbouring plant is essential for designing a bioirrigation based intercropping system.