关键词：大气；土壤系统；种植策略
摘 要：Soils are a source of oxides of nitrogen (NO(sub x) = nitric oxide and nitrogen dioxide), precursors for the production of ozone (O(sub 3)), an air pollutant in the troposphere. Production of nitric oxide (NO) occurs through soil microbial processes using ammonium from nitrogen fertilizer and manure inputs or soil mineral nitrogen (N). Emissions of NO(sub x) were measured in almond, alfalfa, tomato, wheat, and silage corn cropping systems during summer months to obtain estimates of NO(sub x) emissions that could potentially be used in regional models predicting O(sub 3) in the San Joaquin Valley. The lowest average NO(sub x) fluxes (40 g NO(sub x)-N ha(sup -1) h(sup -1)) were measured. These high NOx flux events are difficult to predict.