Forage Responses of Buffelgrass and 'Pretoria 90' Bluestem to Nitrogen and Phosphorus Fertilization in a Subtropical Climate

Abstract

A major land use, especially in drier areas of subtropical regions is for forage production. Nutrient availability, as well as moisture, limit production; however, little is known concerning optimum fertilization practices and how nutrient use interacts with rainfall to affect forage yields. A study was conducted on a sandy upland soil under subtropical conditions to determine the effects of nitrogen (N) and phosphorus (P) fertilization on yield, rainfall use efficiency, nutrient uptake, and apparent fertilizer recovery on improved pastures. Established buffelgrass showed dramatic yield responses to N application, while newly planted Pretoria 90 bluestem showed yield responses to N only after residual nutrients had been depleted. Yield responses to N application were mostly quadratic, showing decreasing benefit from N with increasing N application rate. Smaller yield responses to P occurred in the first 2 years on Pretoria 90 and at higher N application rates on buffelgrass. Rainfall use efficiency (yield per unit of rainfall received) for buffelgrass increased greatly with increasing N application rate. Rainfall use efficiency of newly planted Pretoria 90 increased during each of the first 3 years as the stand developed, but was not greatly affected by N fertilization level. Nutrient contents in both grasses generally increased with increasing nutrient application. Both N and P removal by buffelgrass increased primarily with increasing N application. Apparent N and P fertilizer use efficiency by both grasses was affected very little by rate of application of either nutrient but increased with increasing annual rainfall.