A single nitrogen application maintains wheat yield and quality in dryland Mediterranean Vertisol.

In dryland Mediterranean Vertisols, split nitrogen (N) application is usual in wheat crops. Because of the high clay content of these soils and the low rainfall, a single application might offer ecological and economic benefits without yield loss. We conducted a 5-year study as part of a long-term experiment and compared the split application of N (50% at tillering, 50% at stem elongation phase) with a single application (tillering) in 10 cropping systems resulting from the combination of type of cultivation (no-till and conventional tillage) and 2-year crop rotations (wheat-wheat, wheat-fallow, wheat-chickpea, wheat-faba bean and wheat-sunflower). Depending on the system × crop rotation interaction, a single application of 100 or 150 kg N ha-1 maintained grain yield, protein content and apparent N recovery, with no effect on nitrate content compared with a traditional split application. The average grain yield did not differ between split and single application of N (3.27 and 3.23 Mg ha-1, respectively, for single and split application of 100 kg N ha-1 rate; 3.46 and 3.40 Mg ha-1, respectively, for single and split application of 150 kg N ha-1 rate). The soil nitrate concentration at pre-seeding in the 0-0.3 m layer showed similar results, except in the case of the wheat-faba rotation, with lower nitrate concentration in the sub-subplots of single application and no-till. This work shows that adopting the single N application strategy in rotations on Mediterranean dryland Vertisols will reduce economic and environmental costs. [ABSTRACT FROM AUTHOR]