Soil Organic Matter and Nitrogen Changes During 24 Years of Dryland Wheat Tillage and Cropping Practices

Abstract Soil organic matter and total nitrogen were determined after 24 years of growing dryland wheat ( Triticum aestivum L.) under various tillage and cropping practices in the Southwestern Great Plains. The various tillage practices resulted in significant differences in soil organic matter content when a wheat‐fallow cropping system was used. Values were highest for delayed stubble‐mulch tillage. Differences in soil organic matter content due to tillage practices used were not significant where wheat was grown continuously, but values for continuous wheat were higher than those for wheat‐fallow for comparable tillage practices. Soil total N content was significantly affected by the tillage practice used for the wheat‐fallow, but not the continuous wheat cropping system. Values for continuous wheat were higher than those for wheat‐fallow for comparable tillage treatments. Soil organic matter was closely related to soil total N.