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.

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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

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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Resumo No Brasil, mais de 84% das emissões de N2O e 74% de CH4 são resultantes da agropecuária, e aproximadamente 40% do CO2 emitido tem origem do uso e mudança do uso da terra e florestas. Têm-se percebido uma preocupação em diversas instituições de pesquisa abordando essa temática, aprimorando o conhecimento da dinâmica e principais fatores que governam a emissão dos principais gases do efeito estufa (GEE). Nesse sentido, tecnologias sustentáveis que sigam as premissas da agricultura conservacionista apresentam potencial de mitigação na emissão de GEE, à poder citar o sistema de plantio direto (SPD), uso de plantas de cobertura, adoção de sistemas integrados, entre outras práticas edáficas. Em relação ao SPD, a retenção de CO2 na matéria orgânica do solo justifica o balanço positivo em solos manejados sob esse sistema em comparação ao cultivo convencional. Normalmente solos não perturbados atuam como dreno de CH4, no entanto os sistemas de manejo SPD e convencional ainda carecem de mais estudos, a fim de averiguar seus efeitos na produção de N2O. A forma como o solo é manejado influencia diretamente na emissão de gases e balanço de carbono, logo práticas conservacionistas que visam a proteção do mesmo, são fundamentais para mitigação de GEE.

No-tillage (NT) agriculture represents a great advance in soil conservation in tropical and subtropical zones, occupying more than 32 million ha in Brazil in 2017. No-tillage systems can promote earthworm populations, which can improve soil physical and chemical properties, thus enhancing the benefits of NT for soil conservation and ecosystem services. Furthermore, earthworms can be used as indicators of the quality of NT systems. Here, we summarize the studies that evaluated earthworm populations in NT systems between 1986 and 2016 in Brazil, highlighting important gaps in knowledge. The studies were highly skewed geographically, with most data from southern and southeastern Brazil, and had very little information from the two states with the greatest NT area (Mato Grosso and Rio Grande do Sul) which together represent 43% of Brazilʼs NT area. Abundance values ranged from 0 to 660 ind. m −2 , with a mean of 91 ± 129 ind. m −2 (±SD), and at least 33 species were identified in NT systems. However, 73% of sites were considered to have poor and moderate soil quality based on their earthworm populations, raising concern regarding soil quality levels in Brazilian NT systems. Climate, soil and management conditions are important drivers of earthworm populations in Brazilian NT systems and future earthworm surveys in NT systems should provide ample data on these attributes, as well as on earthworm species, in order to improve their use as soil quality bioindicators. Highlights

The objective of this study was to verify early nitrogen (N) fertilization on maize cultivated in succession to black oats. We conducted three experiments, relating to the 2012/13, 2013/14, and 2014/15 growing seasons, at UFSC-Curitibanos, in a randomized complete block experimental design, with four treatments and four replicates. The treatments were N management strategies in which the amount of N applied to maize was split into pre-sowing, at sowing, and topdressing times: (T1) control with no N application; (T2) 2/3 - 1/3 - 0; (T3) 1/3 - 1/3 - 1/3; and (T4) 0 - 1/3 - 2/3. The biometrics and productive potential parameters of the crop were evaluated. Application of N, regardless of the treatment, increased the yield. In 2012/13, there were no significant differences between the ways in which the N application was split, although they produced a higher yield than the control, resulting in a mean yield of 5,008 kg ha-1. In 2013/14, T2 was similar to T3 and T4, resulting in a yield of 9,858 kg ha-1; in 2014/15, T3 and T4 were similar, with a mean yield of 12,466 kg ha-1, while T2 resulted in a lower yield of 10,487 kg ha-1. When 2/3 of the N is applied pre-sowing, it is only effective when it is associated with the occurrence of a drought period at an early developmental stage of the plants. In adequate rainfall conditions, the early application of N fertilization is only effective when combined with a further 1/3 of the amount of N at sowing, and later as a topdressing.