浙江慈溪不同利用年限水稻土肥力特征的比较

温室盆栽条件下比较了浙江慈溪不同利用年限水稻土（50至2000年）水稻生长与谷物产量的差异，以及无施肥条件下种植水稻对水稻土微生物生物量与转化酶、脲酶活性的影响。结果发现，利用年限较长水稻土上种植的水稻植株相对较高（p 0.10），水稻秸秆、根系及谷粒的生物量均随水稻土利用年限延长而显著增加（p 0.05）；N、P、K等营养元素在植株不同部位的分异状况不同，其中秸秆的全P和全K含量均随水稻土利用年限延长而显著升高（p 0.05），而米粒的全N含量也趋于升高（p 0.10）。温室盆栽试验之后，水稻土的微生物生物量及酶活性与利用年限之间的关系规律和种植水稻之前基本一致，且整体上又趋于下降，即无施肥条件下种植水稻转化利用了土壤部分微生物生物量，并减弱了与碳氮转化相关酶的活性，对保持水稻土的营养水平造成不利影响。结果表明，水稻土的肥力质量历经两千年的长期稻作长盛不衰、粮食生产能力不减反增，而且是在作物有效养分可循环利用（如秸秆还田或外施肥料）的前提下实现持续利用的。

Comparison of fertility characteristics in paddy soils of different ages in Cixi, Zhejiang

A pot-culture experiment was carried out to investigate the growth and production of rice cultivated in five paddy soils in use for 50 to 2000 years, and the effects of rice cultivation without fertilization on microbial biomass and enzyme activities in paddy soils were determined. The shoot length of rice cultivated in paddy soils tended to increase with years of use (p < 0.10), while the biomass of straw, root and grain all increased significantly (p < 0.05). Though the available nutrients were distributed with different ratios in different plant parts, the total N content in grain tended to increase with years of use (p < 0.10), while the total P and K contents in straw increased significantly (p < 0.05). Soil microbial biomass and activities of invertase and urease all tended to decrease after pot-culture experiment, while the correlations between these biochemical properties and field ages were similar to those before this experiment, suggesting that rice cultivation without fertilization consumed part of soil microbial biomass, decreased soil enzyme activities correlated with C and N transformation, and affected soil nutrients status disadvantageously. These results indicated that the fertility quality and the sustainable utilization of paddy soils were based on the recycling of crop available nutrients by straw returning or fertilization.