有机无机肥配施对不同程度盐渍土N2O排放的影响

选取内蒙古河套灌区轻度盐渍土S_1(EC为0.46 dS·m~(-1))及中度盐渍土S_2(EC为1.07 dS·m~(-1))为研究对象,在等施氮量条件下,采用静态箱-气相色谱法研究了不同有机无机肥配施比例:CK(不施肥)、U_1(240 kg·hm~(-2)化肥)、U_3O_1(180 kg·hm~(-2)化肥+60 kg·hm~(-2)有机肥)、U_1O_1(120 kg·hm~(-2)化肥+120 kg·hm~(-2)有机肥)、U_1O_3(60 kg·hm~(-2)化肥+180 kg·hm~(-2)有机肥)和O_1(240 kg·hm~(-2)有机肥)对春玉米农田土壤N_2O排放的影响,旨在明确不同施肥策略下土壤N_2O排放特征,为制定盐渍化农田合理的减排措施提供理论依据.结果表明, 2种不同程度盐渍化土壤N_2O排放存在显著差异,同一处理S_2土壤N_2O排放总量较S_1土壤高出11.86%～47.23%(P0.05).各施肥处理对土壤N_2O排放通量影响趋势基本一致,即施肥后出现排放高峰,基肥和追肥后累积排放量占整个生育期排放量60%左右.适当施入有机肥可以显著降低土壤N_2O排放,S_1和S_2盐渍土分别以U_1O_1及O_1处理N_2O排放量最小,较U_1处理显著降低33.62%和28.51%(P0.05),同时可以获得较高的玉米产量.各施肥处理N_2O排放通量与土壤NH~+_4-N呈极显著正相关关系(P0.01),而与土壤NO~-_3-N含量呈负相关关系,表明硝化作用是盐渍化玉米农田N_2O产生的主要途径,配施有机肥可以持续减少土壤NH~+_4-N供给而减少N_2O的排放.从玉米产量及减少温室效应的角度,得到本地区适宜的施肥管理模式:轻度盐渍土为120 kg·hm~(-2)有机肥+120 kg·hm~(-2)化肥,中度盐渍土为240 kg·hm~(-2)有机肥.

Effects of the Combined Application of Organic and Inorganic fertilizers on N2 O Emissions from Saline Soil

Combining organic fertilizer with chemical fertilizer may affect the microbial processes related to nitrous oxide (N₂O) emissions under different degrees of soil salinization. A mild saline soil (S₁; electrical conductivity (EC) 0.46 dS·m^-1) and moderate saline soil (S₂; 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:U₁ (240 kg·hm^-2 of chemical fertilizer), U₃O₁ (180 kg·hm^-2 of chemical fertilizer+60 kg·hm^-2 of organic fertilizer), U₁O₁ (120 kg·hm^-2 of chemical fertilizer+120 kg·hm^-2 of organic fertilizer), U₁O₃ (60 kg·hm^-2 of chemical fertilizer+180 kg·hm^-2 of organic fertilizer), and O₁ (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 N₂O emissions from the two saline soils. The results showed that the total N₂O emissions from the S₂ soil in the same treatment were between 11.86% and 47.23% higher than those from the S₁ soil (P<0.05). the dynamic trend of the soil N₂O fluxes among the different treatments were similar. The peak N₂O emissions occurred after fertilization, and the N₂O 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 N₂O emission; the S₁ and S₂ saline soils treated with U₁O₁ and O₁, respectively, had the lowest N₂O emissions, whereby there were significant reductions of 33.62% and 28.51% in comparison to the U₁ treatment (P<0.05). Moreover, higher maize yields could be obtained and the N₂O flux was significantly positively correlated with the NH₄⁺-N content (P<0.01) but negatively correlated with the NO₃^--N content. The results demonstrated that nitrification was the main way to produce N₂O in the studied salinized maize farmland, and that the addition of organic fertilizer could reduce the N₂O production by decreasing the soil NH₄⁺-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.