Core Ideas Effectiveness of EEFs varied greatly with their modes of action, soils, and management factors. NIs, DIs, and CRFs reduced N2O emissions by 38, 30, and 19%, respectively, compared with conventional N fertilizers. NIs increased overall crop yields by 7% compared with conventional N fertilizers. DIs might provide added benefits over NIs in alkaline soils, coarse‐textured soils, and irrigated systems. Enhanced efficiency fertilizers (EEFs) have the potential to reduce N2O emissions and improve crop productivity, but the impact of soil and management conditions on their effectiveness is not clear. We conducted a meta‐analysis to evaluate the effectiveness of different EEF types in reducing N2O emissions in three cereal production systems: rice (Oryza sativa L.), corn (Zea mays L.), and wheat (Triticum aestivum L.). We also compared EEF efficacy across soil and management conditions for corn and wheat systems. Results showed that the effect of EEFs on N2O emissions and crop yields varied greatly with their modes of action, soil types, and management conditions. Nitrification inhibitors (NIs), double inhibitors (DIs: urease plus nitrification inhibitors), and controlled‐release N fertilizers (CRFs) consistently reduced N2O emissions compared with conventional N fertilizers across soil and management conditions (grand mean decreases of 38, 30, and 19%, respectively). The DIs more effectively reduced N2O emissions in alkaline soils than did NIs, but the trend was reversed in acidic soils. Urease inhibitors also reduced N2O emissions compared with conventional N fertilizers in coarse‐textured soils and irrigated systems. Overall crop yields increased by 7% with the addition of NIs alone. Compared with conventional N fertilizers, DIs also increased crop yields in alkaline soils, coarse‐textured soils, and irrigated systems. However, CRFs had no effect on crop yields. Overall, this study suggests that NIs or DIs can reduce N2O emissions while improving crop yields. Growers should select EEFs based on their soil and management conditions to maximize their effectiveness.

Soil organic matter (SOM) is essential for sustaining soil health and crop productivity. However, changes in SOM stocks in response to agronomic practices are slow and show years later when it is too late for adjustments in management. Identifying early indicators of SOM dynamics will allow early management decisions and quick remedial action. The objectives of this study were to evaluate long-term effects of tillage intensity and timing on SOM pools and determine the most responsive SOM pools to tillage practice. Soil from a long-term (53 years) winter wheat (Triticum aestivum L.)-spring pea (Pisum sativum L.) rotation and undisturbed grass pasture (GP) in inland Pacific Northwest (iPNW) was sampled to evaluate the effect of four tillage systems [no-till (NT), disk/chisel (DT/CT), spring plow (SP), and fall plow (FP)] on soil organic carbon (SOC, proxy for SOM), total nitrogen (TN), particulate organic matter carbon (POM-C) and nitrogen (POM-N), permanganate oxidizable carbon (POXC), water extractable organic carbon (WEOC), total dissolved nitrogen (TDN), KCl-extractable nitrogen (KEN), microbial biomass carbon (MBC) and nitrogen (MBN), basal respiration (BR), carbon mineralization (Cmin), and metabolic quotient (qCO 2 ). GP had higher levels of SOC pools than cultivated treatments. On average, tillage significantly decreased SOC and TN by 28 and 26%, respectively, compared to GP. Among the cultivated soils, tillage had no significant effect on SOC and TN, except for DT/CT that had slightly higher SOC than FP (P = 0.08). On the contrary, NT and DT/CT significantly (P < 0.05) increased levels of POM-C, POM-N, POXC, WEOC, MBC, BR, Cmin, and qCO 2 over FP or SP. However, tillage did not affect TDN, MBN, and KEN. The C-pools (POM-C, POXC, MBC, WEOC, BR, and Cmin) were more strongly correlated with SOM than the N-pools (TDN, MBN, and KEN), with an exception to POM-N. Under wheat-pea rotation in the iPNW, reduced tillage systems (NT and DT/CT) have a potential to maintain or increase SOM, which can be assessed early through its physical (POM), chemical (POXC, WEOC), and microbiological (MBC, BR, Cmin) indicators. POXC and WEOC were the most sensitive indicators of tillage-induced changes in SOM dynamics.

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Nitrogen losses associated with fertilizer application have negative economic and environmental consequences, but urease and nitrification inhibitors have potential to reduce N losses. The effectiveness of these inhibitors has been studied extensively in irrigated but not in rainfed systems. This study was conducted at Glyndon, MN, under rainfed conditions to assess the impact of urease and nitrification inhibitors on NH3 volatilization, N2O emissions, and NO3− concentrations below the spring wheat (Triticum aestivum L.) rooting zone. Urea (U), urea with urease and nitrification inhibitors (SU), and urea with nitrification inhibitor only (UI) were applied at 146 and 168 kg N ha−1 along with the control treatments. Cumulative NH3 volatilization was reduced by 26%, N2O emissions measured 18 d after planting were reduced by 50% with SU, but no significant reduction was observed with UI compared to U. We did not observe a significant effect of higher N rate on N2O emissions, but lower N application rate (146 kg N ha−1) significantly reduced NH3 volatilization by 26% compared to 168 kg N ha−1. Nitrate concentration below the rooting zone was reduced by applying N at lower rate and also through the use of SU and UI instead of U. Soil inorganic N intensity was significantly related with cumulative N2O emissions. Nitrogen source and rate did not influence grain yield and protein content. This single‐growing season study under rainfed conditions suggests that fertilizer N‐stabilizers can be successfully used to minimize N losses without compromising grain yield and protein content.

Crop species composition and richness exert a strong infl uence on soil C and N dynamics through the proportion of decomposable organic compounds returned to the soil. Under no-till, soil C and N pools were compared for fi ve crop rotations, (1) continuous corn (Zea mays L.; CC), (2) spring wheat (Triticum spp.)-soybean [Glycine max (L.) Merr.; SW-S], (3