Effect of phosphate fertilization on nitrogen use efficiency of forage pastures. 1. Tall fescue pastures

CICORE, P. L.; LAPLACETTE, C.; ERRECART P.; MARINO MA; WYNGAARD, N; BORRAJO C.; BERONE G.; INSUA J.R.

Montevideo

Simposio; 7th Symposium on Phosphorus in Soils and Plants; 2022

National Agricultural Research Institute and School of Agronomy, Universidad de la República, Uruguay

Nutrients deficiencies - mainly phosphorus (P) and nitrogen (N) - often depress forage productivity (FP) in pasture-based systems in the Pampas region (Argentina). Fertilizations are often used to attenuate these deficiencies, but it is necessary to increase the use efficiency of the applied nutrients. The FP and the response to N fertilization (i.e. agronomical N use efficiency, NUE) of TF was studied with and without P supply in rainfed tall fescue pastures. The experiment was conducted from 29-07-21 to 26-11-21 (mean air temperature: 13.2ºC, precipitation: 197 mm, potential evapotranspiration: 330,7 mm) in a tall fescue (Lolium arundinaceum (Schreb.) Darbysh) pasture on a typical Natracualf (pH 8.9, P-Bray 5.8 mg kg-1; organic matter 3.4%). The P treatments (0 and 50 kg P ha-1) and N treatments (0, 50, 100, 200, and 400 kg N ha-1) were applied using a factorial design in randomized blocks with three replications (plots size: 1.5x4 m). Accumulated forage was harvested (0.1 m2, 3 cm above ground level), was dried and weighted to establish the PF (kg DM ha-1). The NUE was calculated as (FPNx- FPN0)/Nx (x is the N level of treatment and N0 the control for each P rate). Potential models were fitted to explain the association between NUE and applied N. Applied N and P increased FP and NUE (p