Effect of plant density and nitrogen levels on grain yield and agronomic efficiency for nitrogen in zero till sorghum

A research to study the effect of planting density and N levels on grain yield and agronomic efficiency for nitrogen of zero till sorghum was conducted in 2014–2015 in randomized block design with factorial concept replicated thrice. The treatments comprised three planting densities (S₁= 30 × 10 cm, 3.3 lakh plants/ha; S₂= 45 × 10 cm, 2.2 lakh plants/ha; S₃= 60 × 10 cm, 1.6 lakh plants/ha) allotted to factor-A and four nitrogen levels (N₀= 0 kg/ha, N₁= 50 kg/ha, N₂= 100 kg/ha, N₃= 150 kg/ha) allotted to factor-B. Maximum grain yield of sorghum was obtained at a plant density of 2.22 lakh plants/ha applied with 150 kg N/ha. When yield is the product of vegetative growth the density-yield relationship is asymptotic. The parabolic response curve is typically a flat topped one with decrease in grain yield on both sides of an optimum. The highest agronomic efficiency for nitrogen was obtained from a planting density of 2.22 lakh plants/ha with the application of 50 kg N/ha.