Different Nitrogen Fertilization Sources, Soil Tillage, and Crop Rotations in Winter Wheat: Effect on Yield, Quality, and Nitrogen Utilization

A two-year field study examined the effect of different sources of nitrogen (N) fertilization, soil tillage depths, and crop rotations on winter wheat yield, quality, and N utilization. Nitrogen fertilization treatments were: mineral N at 100 kg N ha(-1) (Nmin); municipal solid waste compost at 100 kg N ha(-1) of organic N (Ncomp); 50 kg N ha(-1) of both compost and mineral N fertilizer (Nmix); unfertilized control (control). Tillage treatments were conventional and minimum tillage applied on the rotations tomato-wheat, sugar beet-wheat, and sunflower-wheat. The Nmix treatment had the highest yield and N uptake (5.29 t ha(-1) and 157.9 kg ha(-1), respectively). The partial substitution of mineral with organic N fertilizer increased yield by 8% and 33%, and N uptake by 2% and 31%, with respect to Nmin and control treatments, respectively. In comparison with Nmin, Nmix had a higher stability in these parameters throughout years and rotations, and no reduction in grain protein level and in N utilization. Conversely, the Ncomp performance was lower than Nmin and Nmix treatments, and the grain yield was only 12% higher than the control. Tillage affected yield and N uptake only in the year characterized by high rainfall during the vegetative stages, while no significant differences were found in protein content and N utilization in both years. Among the crop rotations, wheat after sugar beet had the highest grain yield (4.91 t ha(-1)) and a good protein content (11.9%), while sunflower and tomato rotations had a lower grain yield (4.35 t ha(-1)) and protein content (10.3%).