Emissão de gases do solo e de excretas de bovinos em integração lavoura-pecuária e pastagem permanente

Abstract

Integrated producti on systems have the potential to mitigate greenhouse gas emissions. The aim of the present study was to assess the greenhouse gases emission from soil and excreta in the crop livestock integration and permanent pasture without and with irrigation. The tria l was conducted at the Universidade Tecnológica Federal do Paraná, Dois Vizinhos Campus. The soil of the region is classified as Latossolo Vermelho. The system for integrating crop livestock (ILP) and permanent pasture was installed in 2015, being in trans ition process, coming from a system of permanent grazing of tifton. In the summer in the area of ILP, maize was cultivated, with base fertilization of 439 kg ha 1 of NPK (8 20 10) and fertilization of coverage of 180 kg ha 1 of N (urea). In the winter, oat s+azévem consortium was sown, with 300 kg ha 1 of NPK (8 10 20) of base fertilization and 90 kg ha 1 of N in cover, and oats+azévem was grazed by steers mestizos. In the permanent pasture in the summer cycle, tifton pasture is maintained, which received 50 kg ha 1 of N. In winter a consortium of oats+azévem in tifton was harvested, which received 90 kg ha 1 of N. crossbred steers were used. In the summer, the treatments in the ILP and permanent pasture were composed of systems fertilized or not, submitted o r not the presence of irrigation. In winter, ILP and permanent pasture were associated with the use of urine and feces as treatments, associated or not with the use of irrigation. The emission of ammonia (NH 3 ) by static semi open system, nitrous oxide (N 2 O ) and methane (CH 4 ) by closed static system, in both soil and summer systems was evaluated. In the period that comprised the corn cycle in the ILP, the NH 3 emission had peaks that reached 12.7 and 8.9 kg ha 1 of N NH 3 in the areas without and with irrigati on, respectively, after fertilization with 180 kg ha 1 of N. In the pasture the peaks reached 1.5 and 1.2 kg ha 1 of N NH 3 in the areas without and with irrigation, respectively, after application of 25 kg ha 1 of N, so the use of irrigation can reduce soi l NH 3 emission after nitrogen fertilization. N 2 O fluxes increased after maize planting, with an emission peak of 821 ug m 2 h 1 of N N 2 O in irrigated ILP and with nitrogen fertilization at 26 days, with peaks of 299 and 504 ug m 2 h 1 of N N 2 O in the areas with and without irrigation, respectively. In the pasture the peaks reached 480 and 288 mg m 2 day 1 of N in the irrigated areas and without irrigation, respectively, with emissions concentrating in the first days after application. The feces in both area s had less intense fluxes, however, they lasted up to 43 days of monitoring, and the total emitted from the feces in relation to urine were higher. The addition of urine to the ILP without irrigation provided emission a 1949 ug m 2 h 1 of N N 2 O, while the peak recorded in the irrigated area was 1610 ug m 2 h 1 of N N 2 O. In the irrigated pasture the N 2 O emission peak was 555 ug m 2 h 1 and in the non irrigated area of 1376 ug m 2 h 1 of N N 2 O. The addition of urine to the soil did not alter the fluxes of CH 4 in both systems, whereas the faeces increased the emissions, reaching peaks of 7707 and 5594 ug m 2 h 1 of C CH 4 in the ILP with out and with irrigation, respectively. The irrigated systems tended to prolong the emission of N 2 O and CH 4 from the excreta in both the land use systems used. The excreta emission factor ranged from 0.13% to 0.39%, below that suggested by the IPCC of 2%.