Applied Nitrogen and Phosphorus Effects on Yield and Nutrient Uptake by High‐Energy Sorghum Produced for Grain and Biomass1

Abstract

AbstractLimited information is available concerning nutrient requirements of high‐energy sorghums (HES) (Sorghum bicolor L., Moench). The purpose of this study was to compare a HES, an intermediate grain cultivar (IGC), and a conventional grain cultivar (CGC) for grain and biomass (stover) yield, responses to applied N and P, and effects on nutrient partitioning and removal. Field experiments were conducted in 1983 and 1984 on Ships clay (Udic Chromustert) near College Station, TX. Nitrogen (0, 84,168 kg N ha−1) and P (0, 15, 30 kg P ha−1) were factorially applied to the three cultivars. Soil nutrient availability decreased after only one year of total dry matter harvesting and was reflected in greater responses to applied N and lower tissue nutrient concentrations and removals the second year. Cultivar and N influenced grain and biomass yields, while applied P had little effect on these parameters. The CGC and IGC produced more grain, but less biomass, than HES. The CGC removed the least nutrients in biomass and the most in grain, while removals by HES components were reversed. Although HES did yield more total dry matter, total crop N and P removals were similiar for all cultivars. HES did remove greater total quantities of all other nutrients. Applied N increased concentrations and uptake of most nutrients in grain and biomass.