Plant Water Stress Effects on Irrigated Grain Sorghum. II. Effects on Nutrients in Plant Tissues 1

A field study was conducted to determine nutrient concentration and dry matter and nutrient accumulation patterns in grain sorghum [ Sorghum bicolor (L.) Moench] plants and to determine the effects of plant water stress on these parameters. Grain sorghum hybrid ‘Pioneer 8311’ was grown under five irrigation treatments to givestress periods varying in timing and duration. Samples were collected at weekly intervals from plants grown with and without stress from (i) early boot until early grain filling, (ii) heading until late grain filling, (iii) early grain filling until near physiological maturiy, and (iv) from early boot until mid‐grain filling. Plants were partitioned into component parts for dry matter estimation and analysis for N, P, K, Ca, Mg, and NO 3 . Plant water stress reduced N and P concentrations in leaves and increased N concentration in stalks and heads, but did not affect NO 3 −N, K, Ca, and Mg concentrations. In unstressed plants, dry matter accumulation proceeded at a near constant rate from about 40 days after planting until physiological maturity. Nutrient accumulation rates tended to be near‐constant from 40 days after planting until flowering and then slowed somewhat. At flowering, plants had accumulated 59, 77, 72, 90, 88, and 65% of their total dry matter N, P, K, Ca, and Mg, respectively. Plant water stress reduced dry matter and nutrient accumulation. Nitrogen and P were affected more than K, Ca, and Mg.