Effects of management on plant production and nutrient cycling on two annual grassland sites

Abstract

Exclusion of sheep grazing had little effect on the system variables. There were only slight differences between the grazed and ungrazed pastures in aboveground and belowground biomass production and nutrient uptake in either year. There were no substantive between-site differences in nutrient transfers. Subclover growth, accompanied with biennial P and S fertilization, resulted in very large increases in biomass production and much larger flows of all nutrients in both years. Largest nutrient fluxes were the transfer of mineralized nutrients through the soil available pool to live plants during the growing season. Most of this actively cycling nutrient supply was stored in standing dead material and litter and was thus retained against leaching between growing seasons. The subsequent fate of these nutrients was then determined by new plant uptake and leaching demands, which showed much annual variation. -from Authors