Growth, Light Interception and Radiation use Efficiency Response of Pigeon pea (Cajanus cajan) to Planting Density in Southern Ethiopia

Planting density is a vital management tool that could be used to enhance productivity. A field experiment was conducted to examine the response of two pigeon pea varieties (ICPL 87091 and ICP 15027) to five planting densities (166666, 200000, 250000, 333333 and 500000 plants ha-1). A split plot design with variety as main plot factor and planting density as sub plot factor was used. Samples were taken every two weeks until physiological maturity starting from 30 Days after Sowing (DAS). The upper two densities, 333333 and 500000 plants ha-1, had greater Leaf Area Index (LAI) and fractional interception (f) during most of the growth period and attained full interception at 105 DAS. The remaining three densities had lower LAI and f and did not attain full interception. Cumulative Intercepted Photosynthetically Active Radiation (CIPAR), extinction coefficient (k) and Radiation Use Efficiency (RUE) increased with rising planting density though moderately for the later. There was a positive linear relationship between dry matter production per area and planting density. Dry matter was significantly correlated with LAI (r = 0.90), CIPAR (r = 0.98) and RUE (r = 0.88). The two varieties had similar productivity potential with similar leaf are indices, CIPAR, k and RUE values. The RUE values obtained were 1.81 g MJ-1 PAR for variety ICPL 87091 and 1.86 g MJ-1 PAR for variety ICP 15027. Because of pigeon pea’s adaptation to drought, it will be useful to study its response to planting density under contrasting moisture levels.