Winter Response of a Native Pasture to Nitrogen Fertilization and Forage Allowance

Abstract

This research was conducted at the Faculty of Agronomy, located in Paysandú, Uruguay, 32º 23’57,86" S y 58º 02' 42,48" O, 61 m s n m. The aim was to study the response in winter production of a native pasture to different levels of nitrogenous fertilizer and herbage allowance. The experiment was led in an experimental central compound rotational design of uniform precision, with two factors with five levels each one: nitrogen (N) (0, 44, 150, 256, 300 kg/ha of N) and herbage allowance (OF) (4,0; 5,5; 9,0; 12,5 and 14,0 kg MS/100 kg of live weight PV), distributed in two blocks. Winter production (MS kg/ha) was the highest with high doses of N and low supply of forage. It was also high under low dose of N and high herbage allowance, revealing some compensation between both factors. The efficiency of fertilizer use peaked at 16 kg MS/kg N, and was similar to the one achieved with cultivated species. The observed response was mirrored in the vegetation quality, estimated from the relation between the biomass of winter and summer species (I/E ratio), which turned out to be the highest with intermediate doses of N. Consecuently, the combination of low levels of N (50 kg/ha) with intermediate herbage allowance (8,0% PV), helped double the average winter production of the native pasture of West Uruguay.