Volatilização de amônia dos dejetos líquidos de suínos aplicados em plantio direto: quantificação e estratégias de mitigação

Abstract

Ammonia volatilization is the primary cause of nitrogen loss from liquid pig slurry (PS). To measure this physical-chemical process and establish strategies for its mitigation is crucial to decrease environmental and economic impacts. The objective of this study was to investigate the utilization of an open collector to capture volatilized ammonia from PS applied in the soil. Also to test strategies of slurry application and management aiming to reduce N loss through NH3 volatilization in corn-wheat crop succession in direct seeding. Two field studies were conducted in an Hapludult at the Federal University of Santa Maria/RS. The first study consists of two experiments after the application of 50 m3 of PS ha-1. The first experiment followed an entirely randomized design with four replications, as follows: control method 1 (methodology adapted from Nômmik (1973)); control method 2 (PET methodology adapted from Araújo et al. (2009)); method 1; method 2; and, method 2 altered. For the second experiment, improvements were made for the method 2, applying a randomized blocks experimental design with four repetitions and three treatments: control method 2, method 2 and method 2 improved. This study was conducted in corn and wheat crops in randomized blocks with four repetitions of the treatments: soil (control); mineral fertilization (NPK + U); PSs - PS in the suffice with 100% of N applied in the seeding; PSi - PS injected with 100% of N applied in the seeding; PSi + PSs - PS injected with 50% of N used in the seeding, and 50% of N applied top-dressing through PS on the surface; PSi + U - PS injected with 50% of N applied in seeding and 50% of N applied top-dressing via Urea. In the first study, the NH3 volatilization in the experiment I were 10.1; 7.8 and 7.4 kg of N-NH3 ha-1, what corresponds to only 10.6; 7.2 and 6.8% of the total NH3 emissions capture by the method 1, method 2 and method 2 altered, respectively. On the other hand, the NH3 volatilization in experiment II were 12.8 and 23.8 kg of N-NH3 ha-1 resulting in 16.7 and 33.4% captured in the method 2 and method 2 improved showing advantages of using open collector. In the second study, the treatment PSi was similar to the control with an annual accumulated loss of 5.3 kg of N-NH3 ha-1. The strategies PSi + PSs and PSi + U resulted in annual losses 5.6 and 3.5 higher than the treatment PSi, respectively. The treatments NPK + U and PSs also obtained significant losses, with annual values of 32.0 and 21.6 kg of N-NH3 ha-1, which corresponds to 10.6 and 7.2% of the total ammoniacal applied in both crops. In this sense, the method 2 improved demonstrated to be a promising methodological alternative to evaluate NH3 from PS application, besides the injection of these in the soil is the best strategy to mitigate the volatilization of ammonia in crops under no till.