No-tillage (NT) has been one of the main advances related to soil management in Brazilian agriculture in the last 30 years. However, its full adoption in lowland areas that are traditionally cultivated with flooded rice is still incipient (<5 %). The main reasons are associated with the soil hydromorphic condition and the management of highly recalcitrant residual crop biomass, demanding soil disturbance even occasionally. This review presents a historical survey about the soil management systems utilized in lowland areas [...] No-tillage (NT) has been one of the main advances related to soil management in Brazilian agriculture in the last 30 years. However, its full adoption in lowland areas that are traditionally cultivated with flooded rice is still incipient (<5 %). The main reasons are associated with the soil hydromorphic condition and the management of highly recalcitrant residual crop biomass, demanding soil disturbance even occasionally. This review presents a historical survey about the soil management systems utilized in lowland areas

Nitrification inhibitors (NIs) and drip irrigation are recommended to mitigate trace gas emissions from agricultural soils. However, studies comparing the effect of different NIs on the release of trace gases from soils with contrasting textures under subsurface (SBD) and surface (SD) drip irrigation are lacking. Therefore, this study aimed to assess the effectiveness of three NIs in mitigating nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄) emissions from two soils with different textures under SBD, with pipe buried in 10 cm depth, and SD. Two greenhouse experiments were carried out with silt loam and loamy sand soil textures cultivated with wheat under SBD and SD to assess the effectiveness of the NIs Dicyandiamide (DCD), 3,4-Dimethylpyrazole phosphate (DMPP), and 3-Methylpyrazol combined with Triazol (MP + TZ). Ammonium sulfate was applied at a rate of 0.18 g N kg soil^-1. The measured variables were daily and cumulative N₂O-N, CO₂-C, and CH₄-C emissions, as well as soil NH₄⁺-N and NO₃^--N concentrations. The NIs and SBD had additive effects on reducing N₂O-N emissions in the silt loam, but not in the loamy sand soil texture. Under SBD, total N₂O-N emissions were 44% and 52% lower than under SD in the silt loam and loamy sand soil textures, respectively. Moreover, DMPP kept the highest NH₄⁺-N concentrations and promoted the lowest N₂O-N release. CO₂-C and CH₄-C total emissions were not affected by the treatments. Our findings supported the hypothesis that SBD decreases N₂O-N emissions relative to SD. Among the investigated NIs, DMPP has the highest effectiveness in retarding nitrification and mitigating N₂O-N release under the studied treatments. Finally, in coarse-textured soils, the use of NIs could be sufficient to significantly abate N₂O-N emissions.

Extensive research has been performed into the effectiveness of nitrification inhibitors (NIs) in preventing N losses; however, tropical agriculture has been underrepresented in recent meta-analyses. Here, we apply a meta-analytic approach using data from 50 articles to identify the impact of NIs (DMPP, DCD, and DCD + NBPT) on crop yield, N₂O emissions, soil NH₄⁺ and NO₃⁻ concentrations, and NH₃ volatilization in subtropical and tropical regions of Brazil. In addition, the survey includes information about location; climate zone; cultivated crops; soil pH; soil organic carbon; soil texture; experimental method; soil management; irrigation; fertilizer source, rate, and type; and NI type and rate. Overall, the data set showed that NIs increased crop yield and soil NH₄⁺ concentrations by 3 and 60%, respectively, whereas N₂O emissions and soil NO₃⁻ concentrations were reduced by 62 and 31%, respectively. Ammonia volatilization was not changed by NI application. However, the combination of a NI with a urease inhibitor decreased such losses by 39%. The effectiveness of the NIs was highest in irrigated fields, fine-textured soils, and mineral N sources. Moreover, NI performance in Brazil was found to be similar in tropical and subtropical climates, and was also comparable to values previously reported in meta-analyses, including those conducted in temperate climates. Therefore, NI application is indicated to be an efficient strategy to delay nitrification and mitigate N₂O emissions in tropical agroecosystems.

Climate change has been intensifying soil drying and rewetting cycles, which can alter the soil microbiome structure and activity. Here we hypothesized that a soil drying-rewetting cycle enhances biodegradation and, hence, decreases the effectiveness of nitrification inhibitors (NIs). The effectiveness of DMPP (3,4-Dimethylpyrazole phosphate) and MP + TZ (3-Methylpyrazol and Triazol) was evaluated in 60-day incubation studies under a drying and rewetting cycle relative to constant low and high soil moisture conditions (40% and 80% water-holding capacity, WHC, respectively) in two different textured soils. The measurements included (i) daily and cumulative N₂O-N emissions, (ii) soil NH₄⁺-N and NO₃⁻-N concentrations, and (iii) the composition of bacterial soil communities. Application of DMPP and MP + TZ reduced the overall N₂O-N emissions under drying-rewetting (-45%), as well as under 40% WHC (-39%) and 80% WHC (-25%). DMPP retarded nitrification and decreased N₂O-N release from the sandy and silt loam soils, while MP + TZ mitigated N₂O-N production only from the silt loam soil. Unexpectedly, between days 30 and 60, N₂O-N emissions from NI-treated soils increased by up to fivefold relative to the No-NI treatment in the silt loam soil at 80% WHC. Likewise, the relative abundance of the studied nitrifying bacteria indicated that the NIs had only short-term effectiveness in the silt loam soil. These results suggested that DMPP and MP + TZ might trigger high N₂O-N release from fine-textured soil with constant high moisture after this short-term inhibitory effect. In conclusion, DMPP and MP + TZ effectively reduce N₂O-N emissions under soil drying and rewetting.

O objetivo deste trabalho foi avaliar os efeitos do sistema plantio direto (PD) e do manejo com preparo convencional (PC) sobre atributos físicos e hídricos de um Planossolo Háplico cultivado com soja, em terras baixas do Sul do Brasil. Amostras indeformadas de solo foram coletadas às camadas de 0,00-0,10, 0,10-0,20 e 0,20-0,40 m, para a determinação dos atributos físico-hídricos, tendo-se monitorado o potencial mátrico do solo com sensores, ao longo de um ciclo de produção da soja. Os valores de macroporosidade foram menores do que 0,10 m³ m^-3, independentemente do sistema de manejo do solo, o que restringe a possibilidade de cultivo da soja em sequeiro, pelo comprometimento da difusão de gases. Comparado ao PC, o PD promove a microporosidade na camada de 0,00-0,10 m, o que aumenta o conteúdo de água armazenada no solo e a disponibilidade hídrica para a cultura da soja, com reflexos positivos sobre a produtividade da cultura.