Impact of N, P, and K rates on stockpiled tall fescue in claypan soils

Stockpiled tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] is an alternative to extend the grazing season and reduce feeding costs during the winter. In addition, adequate fertility management with N, P, and K nutrients can improve forage production. Our objective was to evaluate the impact of N, P, and K fertilization (from 0 to 120 lb/a, 0 and 50 lb/a, and 0 and 30 lb/a, respectively) on forage accumulation (FA) and nutritive value in stockpiled tall fescue in claypan soils. The study was carried out in Columbus, KS, on established ‘Kentucky 31’ tall fescue pastures in the fall of 2019 and 2021 (two years). The treatments were one unfertilized control and fertilization with six combinations of nitrogen (0, 40, 60, 80, and 120 lb/a), phosphorus (0 and 50 lb/a), and potassium (0 and 30 lb/a) rates. Forage accumulation was greater in the treatments with at least 60 lb N/a compared with the unfertilized control (1,235 vs. 570 lb DM/a). However, the greatest crude protein content (CP; 13%) and crude protein accumulation (CPA; 163 lb CP/a) were produced when 120 lb N/a was applied. Nitrogen fertilization also resulted in greater total digestible nutrients, net energy gain, net energy maintenance, and lower acid detergent fiber. Phosphorus and potassium had little effect on the measured responses. Nitrogen fertilization can be an alternative to increase stockpiled tall fescue FA and nutritive value, reducing the need for energy and protein supplementation of livestock during the winter.