长期定位有机物料还田对关中平原夏玉米-冬小麦轮作土壤NO排放的影响

农田土壤是大气光化学活性气体一氧化氮(NO)的主要人为源之一.为定量研究有机物料还田对NO排放的影响,利用静态暗箱法对关中平原26 a长期定位施肥夏玉米-冬小麦轮作农田NO排放通量进行周年(2016年6月至2017年6月)观测.除对照(CK)处理全年不施肥外,田间设3个施肥处理,冬小麦季分别为全化肥(NPK,165 kg·hm~(-2))、化肥加秸秆[NPKS,(165+40)kg·hm~(-2)]和化肥加牛粪[NPKM,(50+115)kg·hm~(-2)];夏玉米季均施等量化肥(188 kg·hm~(-2)).观测期内,CK处理NO排放通量较小[12.2 g·(hm~2·d)~(-1)];各施肥处理均在夏玉米播种、施肥和冬小麦施肥后出现排放峰,其中NPK处理峰值最高[112.0 g·(hm~2·d)~(-1)].各处理NO年排放总量和排放系数分别为0.13~0.57 kg·hm~(-2)和0.04%~0.12%.NPKS和NPKM处理年排放总量较NPK分别减少17.6%和增加68.0%(P0.05).与NPK处理相比,NPKS和NPKM冬小麦季排放总量降低41.1%~60.0%(P0.05);但夏玉米季增加25.2%~292.1%(P0.05).冬小麦季添加有机物料有效降低NO排放,而夏玉米季NO排放增加则与土壤有机质含量有关.

Effect of Long-term Organic Amendments on Nitric Oxide Emissions from the Summer Maize-Winter Wheat Cropping System in Guanzhong Plain

Agricultural soil is a significant source of nitric oxide (NO). The primary aim of this study was to quantify the effect of long-term organic amendments on NO emissions from the summer maize-winter wheat cropping system in Guanzhong Plain. NO fluxes were regularly measured by the static chamber method for one year (June 2016 to June 2017). Field experiments included four fertilizer treatments that commenced in 1990. The control (CK, 0 kg·hm^-2) treatment was unfertilized throughout the years. The fertilized treatments were synthetic fertilizer (NPK, 165 kg·hm^-2), synthetic fertilizer plus maize stalk (NPKS, (165+40) kg·hm^-2), and synthetic fertilizer plus dairy manure (NPKM, (50+115) kg·hm^-2) during the winter wheat season. They were fertilized with synthetic fertilizer (188 kg·hm^-2) during the summer maize season. The results showed small NO emission [<12.2 g·(hm²·d)^-1] from the CK treatment within the experimental period. Large NO fluxes [up to 112.0 g·(hm²·d)^-1 in NPK treatment] were captured following sowing and fertilization during the summer maize season and following fertilization during the winter wheat season for all fertilized treatments. Annual NO emissions and direct emission factors ranged from 0.13 to 0.57 kg·hm^-2 and from 0.04% to 0.12%, respectively. Annual NO emissions from the NPKS and NPKM treatments were 17.6% lower and 68.0% (P<0.05) larger than those from the NPK treatment, respectively. Seasonal NO emissions from the NPKS and NPKM treatments were 41.1%-60.0% (P<0.05) lower than those from the NPK treatment during the winter wheat season, indicating that organic amendments reduced NO emissions. Seasonal NO emissions from the NPKS and NPKM treatments were 25.2%-292.1% (P<0.05) larger than that from the NPK treatment during the summer maize season, mostly due to the positive effect of soil organic matter content on NO emissions.