秸秆还田与施氮对黑土区春玉米田产量、 温室气体排放及土壤酶活性的影响

探讨秸秆还田与施氮对高纬度黑土区春玉米产量与温室气体排放特性的影响,对促进粮食增产和降低环境代价具有重要意义。本研究通过位于黑土区的大田定位试验,利用静态箱-气相色谱计数方法,在秸秆还田与不还田和3个氮素用量(纯N:120 kg·hm~(-2),240 kg·hm~(-2)和300 kg·hm~(-2))条件下,研究了春玉米不同生育时期农田土壤CO2、N2O和CH4综合温室效应与排放强度,以及土壤过氧化氢酶和脲酶活性的变化。结果表明:无秸秆还田时,高氮用量处理春玉米产量最高;秸秆还田后,中等氮用量处理(240 kg·hm~(-2))春玉米产量最高,且与无秸秆还田的高氮处理间无显著差异。无秸秆还田时,随施氮量增加,CO2、N2O和CH4排放量均显著提高,综合温室效应和土壤温室气体排放量与强度显著增加(P0.05);增施氮肥配合秸秆还田,增加了CO2和N2O的排放量,而土壤CH4的碳汇功能增强,温室气体排放量与强度未显著提高(P0.05)。无秸秆还田,增施氮肥降低了土壤过氧化氢酶活性但提高了土壤脲酶活性;而秸秆还田使得增施氮肥引起的土壤过氧化氢酶活性降低的幅度加大但土壤脲酶活性提高的幅度变小。因此,秸秆还田后配合中等用量氮处理(240 kg·hm~(-2))玉米产量最高,且能够抑制单纯增施氮肥对综合温室效应和土壤温室气体排放强度的促进作用,推荐在生产中参考使用。

Effects of soil straw return and nitrogen on spring maize yield, greenhouse gas emission and soil enzyme activity in black soils

Northeast China spring maize production area is among the main maize cultivation regions in China. Due to located in high latitude region and singling cropping system, spring maize fields in black soil region of Northeast China is less reported as for researches on farmland greenhouse effects. It is therefore important to explore the effects of straw return to soil and nitrogen application on maize grain yield and greenhouse gas emissions in the area. In this study, a two-factor straw return (no straw return and straw return) and three-factor nitrogen (N) application (N: 120 kg·hm^-2, 240 kg·hm^-2 and 300 kg·hm^-2) field experiment was conducted in a randomized block design. Total emissions of CO₂, N₂O and CH₄, global warming potential of CO₂-eq and greenhouse gas emissions intensity (GHGI), soil catalase and urease activities were determined in the experiment. The results showed that the highest yield was observed in straw return with medium N dose (240 kg·hm^-2) treatment, which was not significantly different from that of the highest N dose (300 kg·hm^-2) with no straw return treatment (P > 0.05). With increasing N dose, CO₂, N₂O and CH4 emissions, global warming potential of CO₂-eq, and GHGI significantly increased under no straw return conditions. On the other hand, N application with straw return only enhanced CO₂ and N₂O emissions, while soil CH4 carbon sink increased (P < 0.05), and greenhouse gas emissions and intensities (CO₂-eq and GHGI) did not increase remarkably (P > 0.05). Under no straw return conditions, N application reduced soil catalase activity and enhanced soil urease activity with increasing N application. However, straw return improved the decreasing range of soil catalase activity, and weakened the increasing range in soil urease activity caused by increased N application. Therefore, straw return with N application enhanced grain yield, with the highest yield under medium N application treatment (N: 240 kg·hm^-2). Medium N application with straw return limited greenhouse effects compared with no straw return in the experiment. The results were valuable for the recommendation of N application rates in spring maize cultivation in black soil regions.