[Effects of the Combined Application of Organic and Inorganic fertilizers on N 2 O Emissions from Saline Soil].

Combining organic fertilizer with chemical fertilizer may affect the microbial processes related to nitrous oxide (N ₂ O) emissions under different degrees of soil salinization. A mild saline soil (S ₁ ; electrical conductivity (EC) 0.46 dS·m ^-1 ) and moderate saline soil (S ₂ ; EC 1.07 dS·m ^-1 ) in the Hetao irrigation district of Inner Mongolia were selected. Under equal N rates, the study involved five treatments:U ₁ (240 kg·hm ^-2 of chemical fertilizer), U ₃ O ₁ (180 kg·hm ^-2 of chemical fertilizer+60 kg·hm ^-2 of organic fertilizer), U ₁ O ₁ (120 kg·hm ^-2 of chemical fertilizer+120 kg·hm ^-2 of organic fertilizer), U ₁ O ₃ (60 kg·hm ^-2 of chemical fertilizer+180 kg·hm ^-2 of organic fertilizer), and O ₁ (240 kg·hm ^-2 of organic fertilizer). In addition, a blank control treatment (CK) was employed to investigate the effects of different fertilization treatments on the N ₂ O emissions from the two saline soils. The results showed that the total N ₂ O emissions from the S ₂ soil in the same treatment were between 11.86% and 47.23% higher than those from the S ₁ soil ( P <0.05). the dynamic trend of the soil N ₂ O fluxes among the different treatments were similar. The peak N ₂ O emissions occurred after fertilization, and the N ₂ O 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 N ₂ O emission; the S ₁ and S ₂ saline soils treated with U ₁ O ₁ and O ₁ , respectively, had the lowest N ₂ O emissions, whereby there were significant reductions of 33.62% and 28.51% in comparison to the U ₁ treatment ( P <0.05). Moreover, higher maize yields could be obtained and the N ₂ O flux was significantly positively correlated with the NH ₄ ⁺ -N content ( P <0.01) but negatively correlated with the NO ₃ ^- -N content. The results demonstrated that nitrification was the main way to produce N ₂ O in the studied salinized maize farmland, and that the addition of organic fertilizer could reduce the N ₂ O production by decreasing the soil NH ₄ ⁺ -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 ^-2 of urea +120 kg·hm ^-2 of organic fertilizer), and the moderate saline soil:240 kg·hm ^-2 of organic fertilizer.