Song Qiuhua, Li Fengmin, Liu Hongsheng, Wang Jun, Li Shiqing
Key Laboratory of Arid Agrocology, Lanzhou University, Lanzhou 730000, China.
Ying Yong Sheng Tai Xue Bao. 2003 Sep;14(9):1512-6.
This paper studied the effect of different periods of plastic film mulching (M0-no mulching, M30-mulching for 30 days, M60-mulching for 60 days, and M-mulching for whole growth period) on soil microbial biomass carbon (SMBC) of spring wheat field in semi-arid loess plateau. The mean SMBC in 1999 and 2000 was 335.3 and 259.3 mg.kg-1 dry soil, respectively. It was 29.3% higher in 1999 than in 2000. The highest SMBC was recorded at the harvest stage in M treatment for the two years. In 1999, a wet year with more rainfall, the SMBC of M60 and M treatments was significantly higher than those of M0 and M30 in the mid-period of growth, reached its top at the end of the growth period. The highest grain yield was also achieved in M60. It was a dry year in 2000, but rainfall was rich in the latter growth period of spring wheat. SMBC increased at the beginning period of growth, and did not increase during the mid-growth period. It increased again during the latter period of growth, and showed a significant difference among the treatments. At the harvest stage of 2000, SMBC in M0 was the highest among all the treatments. It was similar between M and M60, and lower than that of M30. In the two years, the ratio of C/N ranged between 7.732-9.042, being lower than the threshold of 11.3, and the ratio of C/P was 300.8-719.6, being higher than the threshold of 300. The two parameters showed that the increase of SMBC was inhibited because of the competition of soil available nutrients between soil microbes and crops. These indicated that soil organic matter content was so shortage that it became the key factor to restrict crop productivity. Under this condition, increasing crop productivity through the input of chemical fertilizers would conceal the problem of soil degradation, and result in a further decrease of soil quality. A long term plastic film mulching would make the problem more serious.
本文研究了半干旱黄土高原春小麦田不同时期地膜覆盖（M0-不覆盖，M30-覆盖30天，M60-覆盖60天，M-全生育期覆盖）对土壤微生物量碳（SMBC）的影响。1999年和2000年土壤微生物量碳的平均值分别为335.3和259.3mg·kg-1干土。1999年比2000年高29.3%。两年中M处理在收获期的土壤微生物量碳含量最高。1999年是降雨较多的湿润年份，M60和M处理的土壤微生物量碳在生长中期显著高于M0和M30处理，在生长末期达到最高值。M60处理的籽粒产量也最高。2000年是干旱年份，但春小麦生长后期降雨充沛。土壤微生物量碳在生长初期增加，生长中期没有增加，生长后期再次增加，且各处理间差异显著。在2000年收获期，M0处理的土壤微生物量碳在所有处理中最高。M和M60处理相近，低于M30处理。两年中，C/N比在7.732-9.042之间，低于阈值11.3，C/P比为300.8-719.6，高于阈值300。这两个参数表明，土壤微生物与作物对土壤有效养分的竞争抑制了土壤微生物量碳的增加。这些表明土壤有机质含量严重不足，已成为限制作物生产力的关键因素。在这种情况下，通过施用化肥提高作物生产力会掩盖土壤退化问题，导致土壤质量进一步下降。长期地膜覆盖会使问题更加严重。
