Competitive Indices in Cereal and Legume Mixtures in a South Asian Environment

Core Ideas Cereal‐legume binary mixtures increased forage productivity per unit area compared to cereal‐cereal and legume‐legume binary mixtures. In binary mixtures, pearl millet was marginally more resistant to yield reduction in comparison to sorghum. Soybean suffered the highest yield losses in binary mixtures compared to cowpea and cluster bean. The assessment of competitive performance of mixture components is important for maximizing benefits of intercropping systems. This field study tested binary mixtures of two cereals {sorghum [Sorghum bicolor (L.) Moench] and pearl millet [Cenchrus americanus (L.) Morrone]} and three forage legumes {cowpea [Vigna unguiculata (L.) Walp.], cluster bean [Cyamopsis tetragonoloba (L.) Taub.], and soybean[Glycine max (L.) Merr.]}, along with their sole crops on competitive indices. Sorghum–cowpea binary mixture resulted in a lower green forage yield of sorghum and cowpea by 9 and 36%, respectively, but overall biomass production was increased by 30 and 117% compared to their sole crop equivalents. Partial land equivalent ratios (LER) of all component crops were higher than 0.50, indicating better land use efficiency, except of soybean in binary mixtures with cowpea and cluster bean. However, the highest LER was of sorghum–cowpea (1.55), followed by sorghum–soybean (1.48) and pearl millet–soybean (1.48) binary mixtures. Pearl millet dominated sorghum and all legumes, while cowpea remained a superior competitor among legumes as per aggressivity value (AV) index. The highest crowding ratio (CR) was exhibited by pearl millet in binary mixture with cluster bean indicating its higher competitive ability in comparison to other mixture components. Observed yield loss data indicated that pearl millet was the most resistant crop to yield loss in all binary mixtures, while soybean had the highest yield reduction. In a short term, the highest area time equivalent ratio (ATER) for sorghum–cowpea binary mixture indicated the maximum advantage for this binary mixture compared to other binary mixtures.