[Effects of the Combined Application of Organic and Inorganic fertilizers on N O Emissions from Saline Soil].

Combining organic fertilizer with chemical fertilizer may affect the microbial processes related to nitrous oxide (NO) emissions under different degrees of soil salinization. A mild saline soil (S; electrical conductivity (EC) 0.46 dS·m) and moderate saline soil (S; EC 1.07 dS·m) in the Hetao irrigation district of Inner Mongolia were selected. Under equal N rates, the study involved five treatments:U (240 kg·hm of chemical fertilizer), UO (180 kg·hm of chemical fertilizer+60 kg·hm of organic fertilizer), UO (120 kg·hm of chemical fertilizer+120 kg·hm of organic fertilizer), UO (60 kg·hm of chemical fertilizer+180 kg·hm of organic fertilizer), and O (240 kg·hm of organic fertilizer). In addition, a blank control treatment (CK) was employed to investigate the effects of different fertilization treatments on the NO emissions from the two saline soils. The results showed that the total NO emissions from the S soil in the same treatment were between 11.86% and 47.23% higher than those from the S soil (<0.05). the dynamic trend of the soil NO fluxes among the different treatments were similar. The peak NO emissions occurred after fertilization, and the NO cumulative emission fluxes accounted for nearly 60% of the emissions during the entire growth period. The proper application of organic fertilizer could significantly reduce the soil NO emission; the S and S saline soils treated with UO and O, respectively, had the lowest NO emissions, whereby there were significant reductions of 33.62% and 28.51% in comparison to the U treatment (<0.05). Moreover, higher maize yields could be obtained and the NO flux was significantly positively correlated with the NH-N content (<0.01) but negatively correlated with the NO-N content. The results demonstrated that nitrification was the main way to produce NO in the studied salinized maize farmland, and that the addition of organic fertilizer could reduce the NO production by decreasing the soil NH-N content. Based on the changes in the corn yield and a reduction in the greenhouse effect, suitable organic and inorganic fertilizer management models for the Hetao irrigation area were the mild saline soil:120 kg·hm of urea +120 kg·hm of organic fertilizer), and the moderate saline soil:240 kg·hm of organic fertilizer.