Effect of crop rotation, nitrogen fertilization and management of crop residues on grain yield of winter bread wheat

摘要

The effects of different rotation systems and crop residue management practices on grain yield of winter bread wheat are discussed, by using the data collected during the last 14 years in an ongoing long-term experiment, starting in 1971 in Perugia (Central Italy, 43 deg N lat.), entirely carried out under《rainfed》conditions. Wheat was grown in 10 crop rotations (different crop sequence and rotation length) and in 3 continuous wheat systems, with different nitrogen fertilization levels. These 13 rotation treatments were factorially combined with two crop residue (c.r.) management practices: 1) removal of c.r.; 2) burial of c.r. + nitrogen supply (10 kg per ton of buried dry matter). In the present paper a particular attention is devoted to the relationship between wheat grain yield and level of foot and root diseases (i.e. take-all, sharp eyespot), expressed as percent of diseased plants at the milky-waxy ripening stage. These diseases seem to play a primary role in determining the strong yield reduction recorded for wheat following wheat treatments, respect to wheat in biennial rotations with other crops. On the other hand, the disease level (and crop yield) does not show to increase or decrease significantly as the number of years of continuous wheat increases. The burial of crop residues does not result in an intensification of the disease; this is probably due to the deep ploughing (0.45 m) carried out every year. On the contrary, the burial practice (and the linked highest nitrogen availability in soil) seems to induce a slight reduction of the disease and an increase of the yield, similar to those recorded increasing nitrogen fertilization level in the continuous wheat systems.