UPTAKE AND EXPENSE OF NITROGEN, PHOSPHORUS AND POTASSIUM IN GRAIN SORGHUM DEPENDS ON NITROGEN FERTILIZATION

Abstract

The uptake and expense of nitrogen, phosphorus and potassium in grain sorghum was studied in a field experiment during the period 2017-2018. Hybrid EC Alize was grown under non-irrigated conditions. The applied nitrogen fertilization was in rates 0, 60, 120, 180, 240 and 300 kg N.ha-1. It was established that application of N240 and N300 let to high average uptake of nitrogen (212.0 kg N.ha-1) and phosphorus (125.2 kg P2O5.ha-1) in maturity. The higher removal of 159.9 kg K2O.ha-1 on average was observed at N180 rate. The expense of nitrogen for production of 1 t of grain increased in parallel with the nitrogen fertilization. The highest nitrogen expense of 39.7 - 45.3 kg N.t-1 grain was established when sorghum received 300 kg N.ha-1 and it exceeded the control by 38.8 in 2017 and by 53.6% in 2018. Sorghum plants used 15.5 - 16.6 kg P2O5 an average to form 1 t of
grain and nitrogen fertilization in rates N60-N300 slightly affected the phosphorus expense. Nitrogen fertilization proven increased the expense of potassium for production of 1 t of grain compared to N0 control plants. The increase was by 8.3 -20.0% in 2017 and by 8.0 - 34.0% in 2018. Sorghum plants expensed 23.2 - 24.2 kg K2O on average to form 1 t of grain at nitrogen rates N180-N300. The strong positive correlation was established between nitrogen fertilization with N uptake (0.966**) and N expense (0.997**) and K uptake (0.820*) and K expense (0.870*).