Improving nitrogen efficiency and reducing ammonia emissions in wheat: a strategy using cattle slurry and dicyandiamide1

ABSTRACT Under no-tillage systems, the surface application of cattle slurry may result in significant losses through ammonia volatilization, compromising the nitrogen-use efficiency in wheat. This study evaluated the effects of cattle slurry (CS) application methods (surface vs. injection), with or without the nitrification inhibitor dicyandiamide (DCD), on ammonia (NH₃-N) volatilization, nitrogen-use efficiency and wheat yield, under no-tillage conditions. Two field experiments were carried out in contrasting soils (Oxisol and Ultisol). Pre-sowing NH₃-N losses were strongly affected by the source and application method of N. For the Oxisol, the cumulative volatilization reached 10.67 % of the N applied in the NPK treatment, when compared to 7.80 % in the surface-applied CS and 7.25 % in the injected CS. For the Ultisol, the NH₃-N losses from CS were lower than 1 % of the applied ammoniacal N, and the injection reduced emissions up to 58 %, relatively to the surface application. The injected CS treatment combined with DCD (CSi + DCD) increased the nitrogen uptake by 48-141 kg ha-1, and improved the nitrogen-use efficiency by 1.23-2.53 kg of grains, when compared to NPK. Grain yield was also higher in CSi + DCD, with increases of 20.3 % (Oxisol) and 16.2 % (Ultisol), in relation to NPK. The slurry injection associated with the use of DCD enhanced the N retention, reduced NH₃-N losses, and increased wheat yield, representing an efficient alternative to conventional mineral fertilization in subtropical no-tillage systems.