This thesis contains 8 chapters focusing on the relations between rainfall and crop yields, and on the effects of various tillage and nutrient management practices on erosion, crop yields and water and nutrient use efficiencies. The bases of the study were: desk studies on conservation tillage and on dust storm erosion in China; long-term field experiments conducted in the dry semi-humid region of northern China (Shanxi and Henan); and simulation modelling. The first two chapters provide a brief introduction and background information on the trends in soil conservation and conservation tillage practices on global, national and regional scales, with emphasis on dryland farming of northern China. Chapter 3 analyses the effects of variation in rainfall on crop yields. The next chapter covers tillage and residue effects on rainfed wheat and maize production. Chapters 5 and 6 discuss nutrient dynamics in dryland maize cropping systems with emphasis on grain yield, and water and nutrient use efficiencies and on nutrient balances and soil fertility indices. Chapter 7 presents a scenario analysis of tillage, crop residue, cattle manure and fertilizer application management effects on soil organic carbon dynamics, using the Century model with input from the long-term field studies. The final chapter provides a general discussion and synthesis of the research findings. The consequences for future research and application of conservation tillage are also discussed.
