不同土地利用方式对苜蓿茬地土壤微生物生物量碳、氮的影响

在甘肃庆阳黄土高原,用熏蒸法研究了土地利用方式对紫花苜蓿Medicago sativa后茬土壤微生物生物量碳、氮的影响.结果表明:4龄苜蓿后茬种植小麦Triticum aestivum 2年后,0～5 cm土壤层微生物生物量碳比苜蓿生长地降低70 mg/kg,休闲地仅为苜蓿生长地的40%,施氮肥对土壤微生物生物量碳无显著影响(P＞0.05);苜蓿后茬连续种植小麦2年后,0～5 cm土壤层微生物生物量氮比苜蓿生长地下降28%,而休闲2年后比苜蓿生长地减少69%,施氮肥对微生物生物量氮无显著影响;苜蓿生长地土壤微生物商为4.2%,后茬休闲后则下降至2.7 %.土壤微生物生物量碳、氮可灵敏反映苜蓿后茬地土壤质量的变化.

Effects of land use pattern on soil microbial biomass C and N after 4 years lucerne on the Loess Plateau

A field experiment was conducted during 2001 to 2003 on the Qingyang Loess Plateau, Gansu Province, China. Soil samples at 0-5 and 5-10 cm layer were taken from lucerne plot, wheat or fallow after four years lucerne, fumigation method was used to determine the soil microbial biomass C, N. The results indicated that reduced microbial C of 70 g/kg was found in the 0-5 cm soil layer in wheat plot compared with that under lucerne, microbial C in fallow plot was only 28% of that under lucerne. Microbial N showed the same pattern as microbial C did. N fertilizer application had no significant effects on both microbial C and N for wheat crop after lucerne. Microbial C and N could be a sensitive index to indicate soil fertility changes. The Cmic/Corg ratio was 4.2% for continuous lu- cerne plot, but only 2. 7% for fallow plot.