Ecophysiological Performance, Growth, and Yield of Four Pigeonpea Varieties Under Different Planting Dates and Densities in the Southeastern United States

As the demand of legume crops such as pigeonpea  [Cajanus cajan (L.) Millsp.] is increasing in the United States, extending the growing areas and improving the yield of such crops become an important task. To understand how agricultural management could influence the ecophysiology, growth, and yield of pigeonpea, we conducted a three-year (2010-2012) field experiment in Nashville, TN.  We used a split-plot design considering two planting dates (main factor, early and later planting), four pigeonpea varieties (sub-plot factor, G1, G2, W1 and W3) and three plant densities (sub-plot factor, 295,500, 145,250, and 96,833 pants/ha). Maximum net leaf photosynthesis, stomatal conductance, transpiration, water use efficiency (WUE), soil respiration, plant height, plant stem diameter, leaf area index (LAI), and seed yield were measured over the three years. Results showed there were significant differences in ecophysiology, growth and yield between planting dates, among varieties, and among years. Early planting produced higher leaf photosynthesis and yield compared to late planting. Among four varieties, G2 grow shorter and had lower LAI, but produced higher seed yield compared to other varieties. W1 grew taller than G2 and produced the second highest yield. Planting date did not show significant influences on leaf physiology, LAI and yield. All variables measured showed remarkable variations among three years. Both precipitation amount and pattern during the growing season had significant influences on plant growth and yield. Our results indicated that variety selection and early planting in the southeastern US may improve pigeonpea growth and yield. Irrigation during drought may also significantly enhance plant performance and yield.