Jiangxin Gu

Plastic film mulching (FM) is widely used to increase crop yields and nitrogen (N) use efficiency. Slow‐release fertilisers (SRF) and nitrification inhibitors (e.g., dicyandiamide [DCD]) are promising for reducing soil N losses, but their combined effects on N balance and carbon footprints (CF) in dryland spring maize systems remain unclear. A 3‐year field experiment on China's Loess Plateau evaluated two cropping patterns: non‐mulching (NM) and FM, combined with three fertilisers: conventional urea (CU), SRF and urea with DCD (UD). The study assessed N loss pathways (N ₂ O, NH ₃ , NO ₃ ⁻ leaching), N mineralisation, maize yield and CF. Both FM and SRF/UD reduced NO ₃ ⁻ leaching, with FM‐SRF being most effective while achieving the highest yield (13,981 kg ha ⁻¹ ). FM and SRF/UD had contrasting effects on N ₂ O and NH ₃ , with FM exerting a greater influence. FM increased N ₂ O but decreased NH ₃ , with the smallest N ₂ O rise in FM‐UD and the largest NH ₃ reduction in FM‐SRF. Primary N loss pathways were NO ₃ ⁻ leaching (16%–52%) and NH ₃ volatilisation (53%–83%). FM's impact on CO ₂ emissions was smaller than fertilisation effects; FM‐SRF minimised N mineralisation, enhancing soil organic carbon (SOC) storage and reducing CO ₂ emissions. FM‐SRF achieved the lowest greenhouse gas intensity (GHGI: 0.017 kg CO ₂ ‐eq k g ⁻¹ ). ΔSOC dominated total CF (26%–62%), while N loss contributions were minor (3.4%–8.8%). FM‐SRF achieved the lowest total CF (4680 kg CO ₂ ‐eq ha ⁻¹ ) and lowest CF per unit yield. Thus, SRF is optimal for film mulching spring maize systems, ensuring low CF and N losses in Loess Plateau drylands.

A systematic understanding of nitrous oxide (N₂O) emission and grain yield in winter wheat–summer maize rotation, one of the most important cereal cropping systems in China, is still lacking. The primary aim of this study was to quantify the N₂O emissions and grain yield, as well as responses to mitigation strategies, in this intensively managed agroecosystem. We conducted a pairwise meta-analysis by compiling a comprehensive dataset of annual N₂O emissions (n = 530) and grain yields (n = 352) from peer−reviewed publications. The N₂O emissions increased with nitrogen (N) fertilizer input rates following a linear model (r² = 0.295, p < 0.001), giving a specific emission coefficient and background emission of 0.71% and 0.5 kg N ha⁻¹ yr⁻¹, respectively. The grain yields responded to the N input rates following a linear-plateau model (r² = 0.478, p < 0.001), giving an optimal N input rate and maximum grain yield of 405 kg N ha⁻¹ yr⁻¹ and 15.5 t ha⁻¹ yr⁻¹, respectively. The meta-analyses revealed that reducing N fertilizers (approximately 50% of the full N input), water-saving irrigation, reduced or no tillage, and applying enhanced efficiency fertilizers significantly decreased N₂O emissions (range: −45% to −9%) and increased or did not impact grain yields (range: −1% to 3%). We recommend that reducing agricultural inputs (i.e., N fertilizers, irrigation, and tillage) is a feasible N₂O mitigation strategy in the intensively managed winter wheat–summer maize rotation that can be employed without additional environmental risks.

The net greenhouse gas emissions from upland soils, as indicated by global warming potential (GWP), mainly depend on the soil carbon sequestration and nitrous oxide (N₂O) emissions. The annual changes in surface (0-20 cm) soil organic carbon (SOC) content from 2010 to 2017 and the N₂O emissions from 2014 to 2017 were measured within a long-term fertilization experiment. The objective was to quantify the effect of stalk incorporation on the soil carbon sequestration, annual N₂O emissions, and GWP of a winter wheat-summer maize field in the Guanzhong Plain. The field experiment included three treatments:conventional fertilization (CF), conventional fertilization plus maize stalks (CFS), and an unfertilized control (CK). The CF and CFS treatments received the same amount of urea per year, with nitrogen (N) input at 165 kg·hm^-2 and 188 kg·hm^-2 in the winter wheat season and summer maize season, respectively. The CF treatment retained the stubbles (about 10 cm above ground) when harvesting the winter wheat and summer maize crops. The CFS treatment retained the same wheat stubbles and all maize stalks (containing approximately 40 kg·hm^-2 of N). The CK treatment was unfertilized throughout the year, with the stubble management the same as that in the CF treatment. The results showed that the CK treatment displayed few changes in SOC content and low N₂O emissions, with GWP varying from 0.04 to 0.11 t·(hm²·a)^-1. The SOC contents in the CF and CFS treatments increased linearly with the fertilization years (P2·a)^-1 and 0.97 t·(hm²·a)^-1, respectively. The N₂O emissions from the CF and CFS treatments varied from 1.65 to 5.36 kg·(hm²·a)^-1 and from 3.08 to 7.73 kg·(hm²·a)^-1, respectively. The annual N₂O emissions from the CFS treatment were 43%-94% higher than those from the CF treatment, whereas the difference was only significant between 2015 and 2016 (P2·a)^-1 and from -2.59 to -0.35 t·(hm²·a)^-1, respectively. The cumulative GWP of the CFS treatment was 42% lower than that of the CF treatment between 2014 and 2017. In summary, the studied winter wheat-summer maize field acted as a sink of greenhouse gases under the conventional fertilization regime. The stalk incorporation further favored greenhouse gas mitigation despite the trade-offs between SOC sequestration and N₂O emissions.

The effect of dairy manure amendments to agricultural soil on the yield-scaled nitrous oxide (N₂O) emissions remains unclear. We hypothesize that an optimum ratio of dairy manure to synthetic fertilizers leads to large nitrogen use efficiency (NUE) and small yield-scaled N₂O emissions. The aims of this study were to (1) quantify the variations in the crop yields and N₂O emissions from winter wheat-summer maize cropping systems in Northwest China, (2) determine the responses of the NUE and yield-scaled N₂O emission to the ratio of organic materials to synthetic fertilizers, and (3) evaluate the relationship between the NUE and yield-scaled N₂O emissions. Field measurements were conducted within long- and short-term fertilization experiments between the years of 2014 and 2016. Treatments included synthetic fertilizers, synthetic fertilizers plus crop residues, and synthetic fertilizers plus dairy manure at both sites. The annual grain yields and N₂O emissions varied from 13.3 to 18.0 Mg ha⁻¹ and from 1.3 to 3.6 kg N ha⁻¹, respectively, across the treatments. The yield-scaled N₂O emissions related negatively to the NUE, suggesting that agronomic aims of improving NUE are an effective approach to mitigate N₂O emissions. The ratio of organic materials to synthetic fertilizers was not a significant limit on the NUE and yield-scaled N₂O emissions. We conclude that organic amendments appeared to play a minor influence on the promotion of the NUE and N₂O mitigation.