Bioeconomic efficiency of native pasture fertilization in south Brazil

This research was aimed at evaluating the plant and animal production and the economic response of a native pasture submitted to the application of N-P-K and nitrogen levels during the 1998199 growing season. The experiment was conducted at Estacao Experimental Agronomica of the Universidade Federal do Rio Grande do Sul (EEA - UFRGS). The pasture was fertilized in 1996 using 3000kg ha(-1) of lime and 500kg ha(-1) of 5-20-20. The one third of these amounts was considered as that concerning the 1998199 growing season, in the economic analysis. The treatments were nitrogen (N) levels (zero, 100 and 200kg ha(-1) of N) as urea, in a randomized block design with two plots by treatment. The experimental animals were beef heifers with initial age of 1,5 year-old and average live weight of 160kg. The forage mass, dry matter accumulation rate, green dry matter total production and the AT transformation efficiency in primary production were enhanced by the N level applied (P< 0.1). The treatments 100 and 200kg ha(-1) of N increased the costs in 104.1 and 208.2%, respectively. The treatment 200kg ha(-1) of N presented the greater area live weight gain, the gross margin and the N conversion efficiency in animal product. The greater net financial return was reached when only lime and N-P-K fertilization were applied. The native posture showed a positive response to the fertilizer application, within the amplitude of amount of the input applied in this experiment.