Studies on mineral nutrition of grain sorghum: VIII - effects of phosphorus

Abstract

A greenhouse experiment with nutrient solution was carried out to verify the effects of phosphorus levels on growth, yield and nitrogen, phosphorus, and potassium contents of 5 grain sorghum cultivars. The plants were grown in 20 1 pots in presence either of full stregth solution, or phosphorus diluted to 0.5, 0.2 and 0.1 of normal concentration, and were harvested at maturity (110 days after germination). At harvest, the plants were split into several parts, oven dried and ground. The samples were then analysed for total nitrogen, phosphorus and potassium. Decreasing phosphorus availability caused a cecrease in grain production, although the dry weight of the other plant parts was not affected; sorghum cultivars showed different responses to phosphorus. The levels of phosphorus in nutrient solution had an effect on nitrogen and phosphorus contents, but potassium absorption was not afected. A decrease in translocation of potassium to the sorghum grains with the decrease in phosphorus availability was observed.