Soil nitrification activity and phosphorus uptake by ryegrass after nitrogen fertiliser application

Abstract
A significant correlation was found between percent N and percent P in ryegrass herbage on a soil of low nitrification activity (Wharekohe silt loam) after application of (NH4)2SO4. No correlation was found on a soil of moderate nitrification activity (Waimate North clay loam), or after application of Ca(NO3)2 to either soil. Consideration of soil nitrification activity may explain some of the apparently inconsistent reports in the literature relating to the effect of fertiliser N on nutrient concentrations in pasture herbage.