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Nitrous oxide (N2O) emissions occur as a consequence of the turnover of soil nitrogen (N), but gross N transformations and N2O production are often not studied in combination, so the relationships are poorly understood. Here, we quantified gross N transformations and the N2O production pathway of alkaline fluvo-aquic soils under different fertilization regimes collected from a long-term field experiment in the North China Plain and compared them with six acidic UK soils (one was alkaline for reference) with high soil organic carbon (SOC). We found that nitrification was the dominant N2O production pathway in the alkaline Chinese soil with a contribution of nitrification to N2O emissions (N2Onit) of 81%. By contrast, denitrification was the main N2O production pathway for the acidic UK soils with the contribution of denitrification to N2O emissions (N2Oden) of 66%. Long-term manure applications significantly increased N2Oden, compared to the synthetic N and no N treatments (25% vs. 18%). The N2Onit was positively correlated with gross autotrophic nitrification rates and pH but negatively correlated with gross N mineralization, SOC, soil total N content, and C:N ratios. Our findings highlight the importance of soil pH in controlling the N2O production in cropland soils, and suggest that the increased contribution of denitrification to N2O emissions should be considered, when increasing SOC through long-term manure and straw management for carbon sequestration and soil fertility improvement. [ABSTRACT FROM AUTHOR]

Oil palm agroforestry systems associated with conservation management practices have been proposed as a more sustainable alternative to monoculture. We examined whether oil palm agroforestry systems (less and more diversified) under conservation management contribute to improving soil fertility (an indicator of soil sustainability), using a secondary forest fragment as a reference. We analyzed the effects of the agroforestry systems and the secondary forest on the following variables in the arable layer (0–20 cm) and in the layers along the soil profile (0–5, 5–10, 10–20, and 20–30 cm): active acidity (pH), calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P), aluminum (Al), organic matter, potential acidity (H + Al), potential cation-exchange capacity (CEC), effective cation-exchange capacity (ECEC), Al saturation (AS), and base saturation (BS). Overall, soil acidity was lower in the agroforestry systems than in the forest, in all layers. In the arable layer, the pH, Ca, Mg, K, P, and BS values were higher in the agroforestry systems than in the forest. Liming, inorganic and organic fertilization, and the maintenance of organic matter on the soil may have contributed to improving soil fertility in the oil palm agroforestry systems. Our results suggest that, in the eastern Amazon, oil palm growing in agroforestry systems associated with conservation practices can contribute to the maintenance of soil fertility at adequate levels for the species cultivated in these systems. [ABSTRACT FROM AUTHOR]

Although oil palm expansion has had severe environmental impacts, oil palm also has the highest yield per hectare of any vegetable oil crop. Compared to many other crops, it has the potential to support high complexity habitats, with minimal chemical input, and relatively high levels of biodiversity and ecosystem functioning. However, there has been little synthesis of available research on oil palm management strategies to support delivery of more sustainable cultivation. In this paper, we provide a systematic map compiling all available evidence assessing within-plantation oil palm management practices at the cultivation stage, with a focus on practices that affect biodiversity and environmental processes. Using approaches adapted from systematic review protocols, we catalogued oil palm management publications to provide details of geographic location, year, interventions tested (i.e. agricultural practices), targeted outcomes of interventions, co-occurrences between different interventions and outcomes (including multiple outcomes), and study design. Most studies were conducted in Southeast Asia, with fewer studies conducted in South America or Africa. Twenty-six interventions were observed in the literature, across six categories: soil, understory, within-crop, landscape-level, replanting, and mixed/multiple interventions. The most common interventions tested were landscape-scale interventions, such as maintaining forest fragments/buffer zones, whereas interventions involved in replanting were the least researched. Eight outcomes were considered: soil fertility, soil erosion, water quality and availability, pest control, replanting, maintenance of biodiversity and areas of high conservation value, and reducing air pollution and greenhouse gas emissions. Studies researching biodiversity were the most common, whereas comparatively few studies considered replanting and reducing emissions. Most primary studies were observational, with experimental studies being rarer, especially in biodiversity research. We match our findings to the Roundtable on Sustainable Palm Oil's environmental sustainability criteria to illustrate how policymakers and producers may use our map to access evidence supporting cultivation-stage oil palm sustainability management. This study provides valuable information to inform best management practices and direction for necessary future research. [ABSTRACT FROM AUTHOR]