Nutritional Composition of Grain Legume Leaves and the Impact of Leaf Removal on Yield.

Core Ideas: Soybean, cowpea, and lablab leaves differed in nutritive value.Soybean and cowpea grain yield responded differently to leaf harvesting done at Vegetative Stage 6 (V6).Legume plants from which two leaves (66%) are harvested at V6 may have similar grain yield to those whose leaves are not harvested. Grain legumes can thrive in adverse environments, making them a climate‐smart technology for hunger mitigation. Although several countries rely immensely on grain legumes to meet daily protein intake requirements per capita, the potentiality of leaf utilization for protein and other nutrients has not been widely considered; additionally, insufficient information is available on leaf removal effects on yield and leaf nutritional composition of grain legumes. A 2‐yr experiment was conducted in central Iowa, USA, to determine the effects of leaf removal rates on nutritive value of removed leaf tissue and subsequent grain yield of cowpea [Vigna unguiculata (L.) Walp.], lablab [Lablab purpureus (L.) Sweet], and soybean [Glycine max (L.) Merr.]. Across entries, dry leaf mean nutrient concentration was 229 g kg–1 for CP, and 17,832, 4461, 21,991, 3702, 113, 205, and 86 mg kg–1 for Ca, Mg, K, P, Mn, Fe, and Zn, respectively. Yield and major yield attributes were affected by leaf removal rate in 2014, but not in 2013. In 2014, grain legumes with 0% leaf removal had 20, 32, and 35% greater yield and seeds weighed 6, 11, and 12% more than those with 33, 66, and 99% leaf removal, respectively. Aboveground biomass, yield, and yield components also differed among entries both years. Grain legume leaf utilization as vegetable or forage may improve human and ruminant nutrition by using leaves, especially in developing countries. [ABSTRACT FROM AUTHOR]