On farm beef production declines with increasing age of tropical pastures in the acid soil savannas of Eastern Colombia even if well managed. In a set of observational studies, farm pastures monitored over a span of 6-15 years exhibited yearly decline in liveweight gains during the rainy season (5-10% per year) as the pasture aged, unless proper refertilization and/or other corrective measures were implemented. Nevertheless, when persistent legumes were associated with the grass, weight gains were preserved or declined very slowly. In one case, resting of a grass-only pasture and nitrogen (N) fertilization of a grass-only pasture for seed multiplication also maintained constant weight gains. When grass pastures were undersown to rain-fed rice, initial animal performance over the first one to two years was superior, facilitated by residual fertilization; however, a subsequent sharp decline in animal performance was observed. The principal factor driving pasture decay appears to be lower N supply from soil. Nonetheless, other soil variables could also play a pivotal role such as texture and limited water infiltration. These trends are not unique to the acid soils of the Eastern Plains of Colombia; similar patterns have been documented globally. In alignment with other authors’ findings, it is recommended that regular rotation of tropical pastures with crops be practiced, unless pastures undergo consistent fertilization aimed at replenishing N levels in particular.