秸秆覆盖和施肥对关中灌区夏玉米生长后期土壤呼吸速率的影响

摘要

土壤呼吸是农田层面影响全球尺度碳循环的关键因素之一，对全球大气二氧化碳浓度的影响不可忽视。前人研究显示土壤呼吸与农田耕作模式及施肥有密切的关系，但目前对于免耕条件下秸秆覆盖和施肥对土壤呼吸的影响研究较少。通过大田定位试验，采用GXH-3010E1型便携式红外线分析器测量土壤CO2排放速率，进而分析探讨关中灌区免耕条件下秸秆覆盖和施肥对土壤呼吸的影响以及土壤呼吸对水热因子的敏感性。结果表明，夏玉米(Zea mays L.)秸秆不覆盖不施肥、施氮肥、秸秆覆盖、秸秆覆盖+施氮肥和夏闲5种处理条件下土壤呼吸速率存在明显规律，从8月9日到9月25日土壤呼吸速率整体呈下降趋势，土壤呼吸平均速率表现为施氮肥(7.78μmol·m-2·s-1)>秸秆覆盖+施氮肥(6.06μmol·m-2·s-1)>秸秆不覆盖不施肥(4.81μmol·m-2·s-1)>秸秆覆盖(4.68μmol·m-2·s-1)>夏闲(2.46μmol·m-2·s-1)。施氮肥可以明显提高土壤呼吸速率，施氮肥处理较不施肥不覆盖处理提高61.75%，秸秆覆盖+施氮肥处理较秸秆覆盖处理提高29.49%。秸秆覆盖可以降低土壤呼吸速率，秸秆覆盖+施氮肥处理较施氮肥处理降低22.11%，秸秆覆盖处理较不覆盖不施肥处理降低2.70%。5种处理下秸秆不覆盖不施肥处理、秸秆覆盖+施氮肥和夏闲处理土壤呼吸速率与5 cm耕层土壤温度的相关性最大，秸秆覆盖处理和施氮肥处理分别与10和15 cm耕层土壤温度的相关性最大；秸秆覆盖处理各土层土壤含水率对土壤呼吸速率有显著影响(P<0.05)。研究表明，秸秆覆盖和施氮肥对土壤呼吸有重要影响，施氮肥可以增加温室效应，秸秆覆盖对温室效应有缓解作用。%Soil respiration is one of the key factors of affecting global scale carbon cycle at farmland levels, and the impact can not be ignored to global atmospheric carbon dioxide concentration. Previous studies showed that soil respiration was closely related with tillage and fertilization of farmland, but the research was less about straw mulching and fertilization effects on soil respiration under no-till conditions. In this study, GXH-3010E1 type portable infrared analyzer was used to measure the soil CO2 emission rate and field experiment was taken to explore the impact of straw mulching and nitrogen fertilizer on soil respiration and the sensitivity of soil respiration to heat and water factors under no-tillage conditions in Guanzhong irrigation area. The result showed that under summer maize (Zea mays L.) no straw mulching no fertilization, nitrogen fertilizer, straw mulching, straw mulching + nitrogen fertilizer and summer fallow treatments soil respiration rate had obvious laws and was downward on the whole from August 9th to September 25th, and soil respiration rate peak appeared in the heading period. Average soil respiration rate was nitrogen fertilizer (7.78 μmol·m-2·s-1) > straw mulching + nitrogen fertilizer (6.06 μmol·m-2·s-1) > no straw mulching no fertilization (4.81μmol·m-2·s-1)>straw mulching (4.68μmol·m-2·s-1)>summer fallow (2.46μmol·m-2·s-1). Nitrogen fertilizer significantly increased soil respiration rate. Processing of nitrogen fertilizer than without fertilization and no straw mulching processing increased by 61.75%, and straw mulching+nitrogen fertilizer treatment compared to straw mulch treatment increased 29.49%. Straw mulching could reduce soil respiration. Straw mulching+nitrogen fertilizer treatment than the nitrogen fertilizer treatment decreased 22.11%, and straw mulching processing than less coverage and no fertilization treatment decreased 2.70%. Soil respiration rate had the maximum correlation with 5 cm soil temperature under no straw mulching no fertilization, straw mulching+nitrogen fertilizer and summer fallow, and with 10 cm and 15 cm soil temperature under straw mulching and nitrogen fertilizer, respectively. Soil moisture had significant effects on soil respiration rate (P <0.05) under straw mulching at all tillage layers. The study showed that straw mulching and nitrogen fertilization had important effects on soil respiration, and nitrogen fertilization could increase the greenhouse effect, but straw mulching could alleviate the greenhouse effect.