Effects of fertilization of Brachiaria humidicola cv. Llanero on pasture productivity in the foothills region of the Llanos Orientales, Colombia

In the foothills region of the Llanos Orientales, Colombia the effects of 3 fertilizer treatments, based on regionally available fertilizers: T1 - no fertilizer (control); T2 - basic fertilizer (kg/ha: P 20, Ca 18, Mg 20, K 18, S 31 and N 18); and T3 - basic fertilizer + additional urea (kg/ha: P 20, Ca 18, Mg 20, K 18, S 31 and N 110), were studied on a nondegraded Brachiaria humidicola cv. Llanero pasture located on an acid, infertile Oxisol that had received biannual maintenance fertilizer for 15 years. Each treatment was composed of 4 paddocks of 0.8 ha each, which were rotationally grazed (7 days grazing and 21 days rest) by a group of Brahman Cebu bulls. Forage production during the rest periods was higher in T3 in both the rainy and dry seasons (1,540 and 940 kg DM/ha, respectively) than in T2 (979 and 665 kg DM/ha) and T1 (958 and 613 kg MS/ha). In T3 also CP concentration in rainy season forage was higher (9.9%) than in T2 and T1 (8.4 and 8.1%, respectively). After a total of 250 days of grazing during the rainy (173 days) and dry seasons (77 days), liveweight production was 317, 599 and 870 kg/ha for T1, T2 and T3, respectively, with stocking rates of 2.2, 3.0 and 3.8 animal units/ha (1 AU = 400 kg live weight) in the rainy and 1.6, 2.1 and 3.2 AU/ha in the dry season, respectively. Daily liveweight gains were, in the same order, 589, 782 and 878 g/animal/day in the rainy season and 379, 642 and 721 g/an/day in the dry season. In economic terms, T3 (basic fertilizer plus urea) represented an additional net income of $US 658/ha in comparison with the control treatment and $US 349/ha in comparison with T2. While the study provides evidence that fertilizing of pasture, particularly with N, has potential to contribute to intensification of livestock production in the region, long-term experiments are required to confirm the sustainability of such systems.