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Increasing nitrogen (N) utilization and reducing N losses are a globally accepted strategy for N fertilizer application. However, little information has been reported on the fate of N when urea (U) and nitrification and/or urease inhibitors are used in black soils. Therefore, a two-year field experiment was conducted with three N fertilizer application treatments, including urea-only, urea combined with nitrification inhibitor (U+NI), urea combined with NI and urease inhibitor (UI) treatments. Maize (Zea mays L.) yield, N use efficiency, gas emissions, global warming potential (GWP), and apparent N loss were determined. Compared to the other treatments, the U+NI+UI treatment had the significantly (P < 0.05) highest maize yield (11.2 t ha-1), N recovery efficiency (44.5%), agronomic N efficiency (28.7 kg kg-1) and N partial factor productivity (75.8 kg kg-1). Moreover, the U+NI+UI treatment significantly (P < 0.05) reduced the peak of Ammonia (NH 3) volatilization and nitrous oxide (N 2 O) emissions, cumulative NH 3 volatilization and N 2 O emissions, and apparent N loss compared to the U treatment. Although there was no significant difference in cumulative N 2 O emissions between the U+NI+UI and U+NI treatments, the U+NI+UI treatment significantly (P < 0.05) reduced cumulative NH 3 volatilization by 55.3%, GWP by 16.2%, and apparent N loss by 28.2% compared to the U+NI treatment. Overall, the combination of urea with urease and inhibitors is a good practice to improve maize yield and N use efficiency while reducing environmental impacts in black soil. [Display omitted] • Nitrapyrin-NBPT combination had the lowest GHG, GWP and Nmin loss among N treatments. • Nitrapyrin combined with urea had the significantly highest NH 3 volatilization. • Nitrapyrin-NBPT combination had the highest maize yield, N uptake, N use efficiencies. [ABSTRACT FROM AUTHOR]

Soil ecosystem multifunctionality (EMF), the ability of an ecosystem to perform multiple functions, remains uncertain in its contribution to crop production, especially in the context of long-term fertilization ecosystems. This study was carried out on a 40-year-old long-term fertilization experiment in black soil in China. Soil samples were collected from four treatments: control (CK); nitrogen (N) fertilizer; phosphorus (P) fertilizer; and a combination of nitrogen and phosphorus (NP) in both maize and wheat planting seasons. The results showed significant effects of N, P fertilizers and crop season on soil biotic and abiotic properties, especially on soil enzyme activities. Crop productivity and soil EMF showed a similar pattern across different treatments and both crop seasons, with significant higher values recorded in treatments with N addition (i.e. N and NP). Soil EMF was strongly associated with crop productivity in both maize and wheat seasons, while soil pH had a negative impact on crop yield. Random forest analysis revealed that microbial functional gene structure was significantly correlated with both soil ecosystem multifunctionality and crop yield. This suggested that fertilization leads to alterations in soil nutrients and the composition of functional microbial communities, subsequently impacting ecological functions and crop growth. These findings indicated that mineral fertilizers can enhance crop yield through soil EMF in the black soils, while exerted substantial impact on soil properties, raising concerns about the sustainability of soils under continuous chemical fertilization. • Long-term mineral fertilization improves soil ecosystem multifunctionality. • Soil ecosystem multifunctionality is strongly associated with crop productivity. • Soil pH and nitrate were the dominant variables in determining soil ecosystem multifunctionality. • Functional gene community structure had significant correlation with crop production. [ABSTRACT FROM AUTHOR]

• Fertilizer application promoted microaggregates and silt-clay formations. • Organic material inputs favored C and N retention in macro- and micro-aggregates. • Newly added C was primarily stored in stable aggregates. • Bulk soil remained SOC-deficient under current fertilizer regimes. Long-term cultivation has generated an enormous carbon (C) and nitrogen (N) deficit in black soil. Fertilizer management has been proven to be important to improve aggregate stability and enhance soil C and N stocks, which primarily occur within aggregates. Using a continuous wheat-soybean-maize rotation system in black soil with a 39-year different fertilizer regimes that created a large range in C input (2.03–3.88 Mg C ha−1 yr−1), we investigated long-term fertilization affected soil aggregation and aggregate-associated C and N levels in soil depths of 0–10, 10–20, and 20–40-cm, and assessed aggregate-associated soil organic carbon (SOC) saturation behavior. Across soil depth intervals, application of synthetic fertilizer with or without manure increased macroaggregate turnover, which increased release of silt and clay (SC) within macroaggregates and promoted formation of free microaggregates (free-m) and free-SC. Fertilization increased organic material (straw and manure) input and greatly favored C and N sequestration in macroaggregates (mainly within the SC fraction, because of the high mass proportion) and free-m. Significant linear relationships were observed between the C content in the soil aggregate fraction and C input, indicated that the added C was primarily stored in stable aggregates, suggesting that bulk soil remained SOC-deficient under current fertilizer regimes. Overall, application of large amounts of organic material is an adequate soil management strategy to improve the structure of black soil and increase soil organic carbon and nitrogen sequestration. This strategy will be useful for agricultural sustainable development and mitigation of climate variability. [ABSTRACT FROM AUTHOR]