Effect of pasture on subsequent wheat crops on a black earth soil of the Darling Downs. II. Organic C, nitrogen and pH changes

Abstract

During the 11 year period 1958 to 1968, continuous cropping to wheat was compared with a rotation involving 3 or 4 years of lucerne-prairie grass pasture followed by wheat, on a Darling Downs black earth. Soil chemical measurements made at various times showed that 2 to 4 years of lucerne based pasture increased organic carbon, total N, mineralisable-N, while pH decreased. Soil total N build-up maximised after 2 years of pasture while the residual effect of 3 or 4 years pasture produced significantly higher nitrate-N levels in soil for up to 7 years, and was related to wheat yield and quality improvements.