Effect of phosphate fertilization on nitrogen use efficiency of forage pastures 2. Annual Ryegrass

CUADRO, R.; CICORE, P. L.; LATTANZI, F. ; ERRECART P.; BERONE G.; MARINO. MA; BORRAJO C.

Montevideo

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

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

Pasture response to N fertilization and the nitrogen use efficiency (NUE) is highly conditioned by the phosphorus (P) availability and soil water. The objective of the study was to evaluate the effect of NP fertilization on the NUEof annual ryegrass, in two growth periods. Two experiments were installed on a Clay loam, Vertic Argiudoll soil (P level citric acid methods: 4.3 mg kg-1; pH= 5.8) in Uruguay. P levels were applied at sowing (0, 15, 30 and 45 kg P ha-1) and six levels of N (0, 40, 80, 150, 300 and 600 kg N ha-1) were applied on 15 June (winter experiment, E1) and on 24 august (spring experiment, E2). The accumulated biomass (BA) was evaluated during periods June- August (80 days, main air temperature 11.5 °C, precipitation 143 mm) and September-November (60 days, main air temperature 17.0 °C, precipitation 264 mm) for E1 and E2, respectively. The NUE was calculated as (BANx- BAN0)/Nx (x is the N level of treatment and N0 the control for each P level). In both periods, the NUE decreased with increasing N levels. In E1 (Figure 1a) N and P application increased the NUE (p