【摘要】 研究了黄绵土区不同覆膜时期对旱作麦田土壤微生物数量及其与土壤碳、氮、磷含量的关系。丰水的 1 999年 ,土壤微生物数量增长早 ,延续时间长 ,覆膜 60 d微生物数量最高 (3 3 .93 8× 1 0 6 /g dry soil) ,其次为全程覆膜 (3 2 .2 5 9× 1 0 6 ) ;干旱的 2 0 0 0年微生物平均数量只有 1 999年的 3 6.5 % ,在后期有一定降水后微生物数量才出现高峰 ,以全程覆膜数量最高(1 4.83 6× 1 0 6 ) ,覆膜 60 d次之 (1 1 .5 2 9× 1 0 6 )。 1 999年各类群微生物数量同土壤有机碳之间均呈显著或极显著负相关。2 0 0 0年相关系数几乎全面下降 ,氨化细菌、硝化细菌和反硝化细菌 ,甚至微生物总量同土壤有机碳之间都已不再显著相关。 1 999年土壤全氮同氨化细菌、硝化细菌、亚硝化细菌、解磷细菌及微生物总量均呈显著或极显著负相关 ,2 0 0 0年只与氨化细菌、亚硝化细菌、微生物总数显著负相关。土壤速效磷含量在 1 999年与解磷细菌显著负相关 ,而在 2 0 0 0年相关已不再显著。两年试验结束后 ,全程覆膜处理有机质下降 2 1 .2 % ,覆膜 60 d处理下降 1 7.2 % ,覆膜 3 0 d和不覆膜处理下降相对较小 (4 .3 %和 6.7% )。由于施用化肥 ,土壤全氮有明显升高。速效磷在 1 999生长季和随后的休闲期都有升高 ,在干旱的 2 0 0 0?更多还原

【Abstract】 Effect of various mulching durations with plastic film on soil microbial quantity and plant nutrients of the spring wheat field was investigated in semi\|arid Loess Plateau of northwest China for two years. Four treatments were employed: M 0\|no mulching, M 30 \|mulching for 30 days from sowing, M 60 \|mulching for 60 days, and M\|mulching for whole growth period. In 1999, a wet year with rich precipitation, the total soil microbial quantity increased faster and the higher level of soil microbial quantity lasted for longer time in the mulching treatments than in control. The highest quantity of soil microbes in total was recorded in the M 60 treatment with 33 938×10\+6/g dry soil, the secondary was in M treatment with 32 259×10\+6/g dry soil at the harvest stage. In 2000, a dry year, the mean quantity of all the microbes for all treatments decreased by 63 5% compared with that in 1999. Because rich precipitation occurred in the latter growth period of this year soil microbial quantity for all the treatments increased significantly, and reached the highest in M treatment with 14 836×10\+6/g dry soil, and the secondary was in M 60 with 11 529×10\+6/g dry soil at the harvest stage of spring wheat. \;Significantly negative correlation was noticed between soil organic carbon contents and the microbial quantities of various physiological properties which included ammonibacteria, nitrite bacteria, nitrate bacteria, denitrobacteria, cellulose decomposing bacteria,phosphorus bacteria and actinomycetes in 1999. In 2000, however, the correlation coefficients decreased between soil organic carbon contents and the quantities of almost all the microbes above mentioned. No significant correlation was found between soil organic carbon contents and some soil microbes such as ammonibacteria, nitrite bacteria, denitrobacteria, even the total quantity of soil microbes. Significantly negative correlation was shown between soil total nitrogen contents and the soil microbial quantities of ammonibacteria, nitrite bacteria, nitrate bacteria, phosphorus bacteria and all the soil microbes in 1999, but no significantly correlation was found between soil total nitrogen contents and the quantities of nitrite bacteria, phosphorus bacteria and all the soil microbes in 2000. Significantly correlation occurred between soil available phosphorus content and quantity of phosphorus bacteria in 1999, no significantly correlation in 2000. \;Soil organic carbon content decreased by 21 2%, 17 2%, 4 3% and 6 7% for M, M60, M30 and M0 treatments, respectively, for the two experimental years. This means that mulching with plastic film for a long period each growth period would result in rapid decomposition of soil organic matter. Because of chemical fertilizer application in sowing periods total nitrogen contents increased significantly in all the treatments. Available phosphorus contents increased significantly in all the treatments during the first growing period of 1999 and the following fallow period, but decreased greatly during the second growing period of 2000. \;It is concluded that mulching with plastic film in dryland farming system promotes activity of soil microbes, accelerates the decomposition of soil organic matter, and releases nutrients for plants. However, because of rapid decomposition of soil organic matter soil holding capacity to fertility decreases seriously, which would damage flexibility, stability, and sustainability of agro\|ecosystem. Therefore, maintaining and improving soil organic matter content through increasing input of organic matter input into field should be paid attention in agro\|ecosystem management under the condition of plastic film mulching.更多还原