CROP ROTATION UNDER NO-TILLAGE IN TIBAGI (PARANA STATE, BRAZIL). II-CO2 AND N2O EMISSIONS

The agricultural activity can change the quantity and quality of soil organic matter (SOM), resulting in CO2 and N2O emissions from the soil. No-tillage (NT) with legume species in crop rotation is a strategy that should be considered not only to increase the SOM quantity, but also to reduce greenhouse gas emissions. The objective of this study was to determine the soil-atmosphere gas emissions with greenhouse effect CO2 and N2O). For this purpose, an experiment was installed in Tibagi (Pat-and State, Brazil), on a clayey Oxisol (Typic Hapludox). The treatments were conducted in non-random strips with subdivided plots: no-tillage crop successions corn/wheat and soybean/wheat (NT12 M/T and NT12 S/T, respectively) for 12 years and no-tillage (NT22 M/T and NT22 S/T, respectively) for 22 years. The CO2 soil emissions were nearly 20 % higher in NT22 than in NT12. The CO2 emissions were significantly correlated (R-2 = 0.85; p < 0. 05) with soil temperature, with 40% lower mean emissions in the months of minimal soil temperatures. Highest N2O emissions were observed after the summer crop harvest, mainly in corn I wheat compared to soybean/wheat succession. N2O emissions were approximately 25% higher after N-fertilizer application to wheat in both crop successions, and were significantly correlated (R-2 = 0.88, p < 0.01) with soil water-filled pore space (S-r %).