Agricultural intensification has been associated with increased greenhouse gas (GHG) emissions. Using integrated crop-livestock systems (ICLs) under no-till agriculture can increase soil organic carbon (SOC) accumulation, thereby helping mitigate such emissions. The aim of this study was to assess the net global warming potential (net GWP) of no-till ICLs at variable grazing intensities of winter black oat pasture in a subtropical ecosystem. A 3.5-year field experiment involving three different grazing intensities (i.e., intensive, moderate and light as defined by a pasture height of 10, 20 and 30 cm, respectively) and grazing exclusion in winter and no-till soybean cropping in summer was conducted on a Ferralsol in southern Brazil. Net GWP, in Mg CO 2 eq ha −1 year −1 , was assessed in terms of SOC sequestration relative to intensive grazing as a reference, including methane (CH 4) and nitrous oxide (N 2 O) emissions, and energy costs of farming operations and inputs. Moderate grazing reduced net GWP relative to intensive grazing (from 0.09 to 4.92 Mg CO 2 eq ha −1 year −1), the latter leading to the highest GWP levels. The decrease in net GWP was mainly the result of SOC accumulation, which offset 34-98% of all GHG emissions. Light grazing and grazing exclusion proved to be less efficient than moderate grazing in decreasing net GWP (1.84 Mg CO 2 eq ha −1 year −1 on average), mainly as a result of decreased SOC accumulation. Based on our findings, moderate grazing (20 cm high pasture) of winter black oat pasture is an effective strategy to reduce the C-footprint of ICLs in subtropical no-till agriculture. Highlights • On-farm assessment of net GWP in subtropical no-till ICLs • Conversion from intensive to moderate grazing reduced net GWP • SOC accumulation is the main driver of net GWP reduction under no-till ICLs.

Índice de área foliar e SPAD durante o ciclo da soja em função da densidade de plantas e sua relação com a produtividade de grãos Leaf area index and SPAD during the soybean development cycle at different plant densities and their relation to grain yield

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Nitrogen (N) gas losses can be reduced by using enhanced‐efficiency N (EEN) fertilizers such as urease inhibitors and coating technologies. In this work, we assessed the potential of EEN fertilizers to reduce winter losses of nitrous oxide (N2O‐N) and ammonia (NH3‐N) from a subtropical field experiment on a clayey Inceptisol under no‐till in Southern Brazil. The EEN sources used included urea containing N‐(n‐butyl) thiophosphoric triamide (UR+NBPT), polymer‐coated urea (P‐CU) and copper‐and‐boron‐coated urea (CuB‐CU) in addition to common urea (UR) and a control treatment without N fertilizer application. N2O‐N and NH3‐N losses were assessed by using the static chamber method and semi‐open static collectors, respectively. Both N2O‐N and NH3‐N exhibited two large peaks with an intervening period of low soil moisture and air temperature. Although the short‐term effect was limited to the first few days after application, UR + NBPT urea decreased soil N2O‐N emissions by 38% relative to UR. In contrast, urease inhibitor technology had no effect on NH3‐N volatilization. Both coating technologies (CuB‐CU and P‐CU) were ineffective in reducing N losses via N2O production or NH3 volatilization. The N2O emission factor (% N applied released as N2O) was unaffected by all N sources and amounted to only 0.48% of N applied—roughly one‐half the default factor of IPCC Tier 1 (1%). Based on our findings, using NBPT‐treated urea in the cold winter season in subtropical agroecosystems provides environmental benefits in the form of reduced soil N2O emissions; however, fertilizer coating technologies provide no agronomic (NH3) or environmental (N2O) advantages.

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