Effect of Five Nitrogen Sources Applied at Four Rates to Pangola Grass Sod Under Humid Tropical Conditions

Abstract

The effects of applying ammonium sulfate, urea, ammonium nitrate, urea + CaCO₃, and ammonium-nitrate-lime (ANL) at the rate of 0, 170, 340, and 510 pounds of nitrogen per acre yearly to a Pangola grass pasture growing on a Ultisol under humid tropical conditions were determined over a 3-year period. Although the differences were not marked, ammonium sulfate was generally the most efficient and urea the least efficient provider of nitrogen to the Pangola grass pastures. The various nitrogen sources did not affect the phosphorus, potassium, calcium, or magnesium content of Pangola grass. Ammonium sulfate applications, and to a lesser extent urea and ammonium nitrate, increased exchangeable aluminum and decreased pH and exchangeable base content of the soil. Mixing lime with urea or ammonium nitrate did not affect their efficiency as suppliers of nitrogen to the grass, yet maintained soil acidity at levels similar to those of plots receiving no nitrogen.