Nitrogen (N) deposition is a vital process of N cycling and is consequently important for the evaluation of N budgets. However, the character and quantity of N deposition inside the horticultural greenhouse remain unknown, impeding a deep understanding of N cycling among soil, vegetable and atmosphere. Here, we measured the dry and wet N deposition, and disentangled the relative percentages of ammonia (NH3) and nitrogen oxides (NOX) gases deposition based on the greenhouse vegetable cultivation experiment. Results found the annual N deposition, was 7.2-17.5 kg N.ha(-1) under different chemical/organic N fertilizer managements, consisting of 77.0%-85.5% by dry deposition and 14.5-23% by wet deposition. The proportions of N deposition from NH3 and NOX emissions ranged within 37.5-83.0% under different N managements. The NH3 emission was the dominant driving factor of dry N deposition, while soil moisture was the dominant driving factor of wet N deposition. Controlled-release fertilizer combined with organic fertilizer resulted in the lowest N deposition (10.2 kg N.ha(-1)) and NH3 and NOX emissions (12.5 kg N.ha(-1)), which could be recommended as the mitigation strategy in greenhouse cultivation. This study investigated the dry and wet N deposition characteristics and their influencing factors, as well as the proportion of N deposition attributed to NH3 and NOX emissions, which provides preliminary understanding of N deposition and the reactive N gas diffusion from greenhouse into the atmosphere.

为揭示未来气候变化趋势对稻谷Fe、Zn含量和积累量的影响,本研究利用开顶式气室(Open Top Chamber,OTC)系统模拟大气CO2浓度上升(EC处理,+100 μL·L-1)和增温(ET处理,+1.5℃)以及二者相互作用(ETEC处理,+1.5℃,+100 μL·L-1)的气候变化情景,对江汉平原2017-2019年双季稻籽粒Fe、Zn以及植酸含量进行持续3a的大田试验观测.结果表明:双季稻籽粒Fe和Zn含量对大气CO2浓度上升与增温的响应存在较大的年际间差异,其中对大气CO2浓度上升的响应较增温更为敏感.与对照(CK)相比,EC处理显著降低2018年晚稻籽粒Fe含量(-13.41%,P＜0.05),显著增加2019年早稻和晚稻籽粒Fe含量(+29.70%和+27.95%,P＜0.05);ET处理显著降低2018年早稻籽粒Zn含量(-13.49%,P＜0.05).就3a观测平均值而言,EC处理显著降低早稻籽粒Zn含量(-8.28%,P＜0.05),而ETEC处理显著降低晚稻籽粒Zn含量(-10.91%,P＜0.05).本研究发现CO2浓度上升与增温叠加作用效果有别于各单因子影响,尤其对高温干旱年份晚稻籽粒Zn含量的降低具有显著的正协同效应.本研究预测未来气候变化可能增加稻米食用人口出现"隐性饥饿"的风险.

A field experiment is conducted in Jianghan Plain using static chamber-gas chromatography method to monitor greenhouse gas emissions from 5 different rice cropping systems:Early rice,late rice,middle rice,rice-crayfish coculture and ratooning rice systems.The emission characteristics of methane and nitrous oxide fluxes,global warming potential and greenhouse gas emission intensity in different rice patterns are analyzed,aiming to provide scientific references for accurate estimates of greenhouse gas emissions from rice paddy.The results show that methane emissions are concentrated in the early flooding stage of rice paddy,with a flux peak of(85.7 mg·m -2 ·h -1 ) for rice-crayfish system,which is higher than those of other patterns by 71.7%-191.5 %.Nitrous oxide emissions are mainly observed during mid-season drainage or after nitrogen fertilization,and the highest flux peak is found for ratooning rice(1100.7 μg·m -2 ·h -1 ),which is 16.8%-654.9% higher than other patterns.The sequence of accumulated methane emission from largest to smallest is rice-crayfish(541.1 kg·hm -2 ),ratooning rice(293.7 kg·hm -2 ),early rice(177.2 kg·hm -2 ),late rice(133.7 kg·hm -2 ),and middle rice(115.3 kg·hm -2 ).For nitrous oxide emission,the sequence is ratooning rice(5.1 kg·hm -2 ),early rice(2.1 kg·hm -2 ),late rice(1.0 kg·hm -2 ),middle rice(0.6 kg·hm -2 ),and rice-crayfish(0.4 kg·hm -2 ).As for total emission calculated by global warming potential,the value of rice-crayfish is 13657.7 kg·hm -2 ,followed by ratooning rice(8857.0 kg·hm -2 ),early rice(5067.3 kg·hm -2 ),late rice(3647.0 kg·hm -2 ),and middle rice(3053.8 kg·hm -2 ).Rice-crayfish is also accompanied by high greenhouse gas emission intensity reaching up to 1.4 kg·kg -1 ,followed by early rice(0.79 kg·kg -1 ),ratooning rice(0.57 kg·kg -1 ),late rice(0.53 kg·kg -1 ),and middle rice(0.34 kg·kg -1 ).The total emission and intensity of middle rice is significantly smaller than those of rice-crayfish system by 77.6% and 75.7 %.It is notable that methane emission accounts for 82.9%-99.0% of total emission among different rice cropping patterns,indicating that controlling methane is key for low-carbon production.Due to water flooding in rice paddy,nitrous oxide emission is small.The high emissions from rice-crayfish paddy are mainly attributed to the long duration of flooding,straw returning and large amount of fodder input,which has led to a long period of soil anaerobic condition,and plenty of carbon substrate for methane production.Thus,it is important to explore methane reduction practices and strategies in rice-crayfish paddy.The emission intensity of middle rice is the lowest due to paddy-upland rotation and can be considered as a low-carbon rice cultivation pattern.

Variations in the climate constitute a significant threat to the productivity of food crops in the Gambia. A good understanding of the influence of climate variability on crop production is vital for climate resilience and improved food security. This study examined the trends, relationships, and the extent to which growing season temperatures and the SPEI (Standardized Precipitation and Evapotranspiration Index) impacted sorghum, millet, maize, and rice yields in three agro-ecological regions of the Gambia during 1990–2019. Mean temperatures and the SPEI exhibited increasing trends while observed yields showed a decline across all regions. The SPEI had a significant positive relationship with yields, and temperatures were negatively associated with yields. Though yield response to climate variability differs among regions, 20% to 62% of variations in the four crop yields were due to climate trends. The combined effect of the SPEI and temperatures decreased yields from 3.6 kg ha−1 year−1 to 29.4 kg ha−1 year−1, with the most severe decline observed in rice and maize yields in the Sahelian zone. Although uncertainties might arise from not considering related extreme climate events, this study highlights how past climate trends affect cereal yields in the Gambia; thus, any unfavorable change in the local climate could have severe repercussions on the country’s food security. There is a need for concerted efforts to increase investments in adaptation strategies to lessen the effects of the climate for improved crop productivity.