地膜覆盖对黄土高原旱作春玉米田土壤碳氮组分的影响

Effects of Plastic Film Mulching on Soil Carbon and Nitrogen Fractions in a Dryland Spring Maize Field on the Loess Plateau

基于2年田间试验,研究了地膜覆盖对旱作春玉米田土壤有机碳、全氮及其组分的影响,试验包括地膜覆盖玉米田、无覆盖玉米田和裸地休闲3个处理,分层测定了0—40cm土层有机碳、全氮、颗粒有机碳氮、潜在矿化碳氮和微生物量碳氮含量。结果表明:在0—40cm土层,各处理间土壤有机碳和全氮含量均无显著差异。与不覆盖相比,地膜覆盖处理0—40cm土层颗粒有机碳氮及其所占比例分别降低了29.0%,33.3%,29.9%,35.7%;0—10cm土层潜在可矿化碳及其所占比例分别降低了17.8%和16.1%,潜在可矿化氮和微生物量碳及其所占比例无显著差异,但在0—10cm土层地膜覆盖微生物量氮含量及其所占比例分别较不覆盖处理提高了10.6%和10.5%(p<0.05)。与裸地休闲相比,无覆盖处理0—40cm土层潜在可矿化碳氮分别提高了12.8%和14.7%,地膜覆盖处理则分别提高了7.8%和6.5%(p<0.05),但种植玉米降低了微生物量碳氮含量及其所占比例。在0—40cm土层覆盖与否对潜在可矿化碳氮和微生物量碳氮影响不显著。总体来看,地膜覆盖能够在一定程度上提高表土微生物量氮组分及其所占比例,但显著降低了中活性碳氮组分含量及其比例,不利于长期的土壤碳氮固定。

The effects of plastic film mulching on soil organic carbon and nitrogen fractions were investigated in a spring maize field.Three treatments,i.e.plastic film mulching,no mulching,and bareland fallow were included and soil organic carbon（SOC）,total nitrogen（STN）,particulate organic carbon and nitrogen（POC,PON）,potential carbon and nitrogen mineralization（PCM,PNM）,and microbial biomass carbon and nitrogen（MBC,MBN）were measured at 0-40 cm soil depths.No significant differences in SOC and STN were found among treatments for all soil depths.Compared with no mulching,the contents of POC,PON,POC/SOC,and PON/STN at 0-40 cm soil depth was decreased by 29.0%,33.3%,29.9%,and35.7% by plastic film mulching,respectively.The PCM content and PCM/SOC was decreased by 17.8%and 16.1%,respectively,and the MBN content and MBN/STN at 0-10 cm soil depth was increased by10.6% and 10.5%（p〈0.05）,respectively.Compared with the bareland fallow,the content of PCM and PNM at 0-40 cm soil depth was increased by 12.8% and 14.7% by no mulching,respectively,and was increased by 7.8% and 6.5%（p〈0.05）by plastic film mulching,respectively.The contents of MBC and MBN and their contributions decreased after maize planting in spite of plastic film mulching or not.In general,plastic film mulching could increase microbial biomass nitrogen at the top layers but decrease both the contents and conributions of moderate labile fractions,indicating that plastic film mulching may not be beneficial for long-term soil nitrogen sequestration in dryland maize fields.