【作者】 杜连凤；

【导师】 张维理；

【作者基本信息】 中国农业科学院 ， 植物营养学， 2005， 博士

【摘要】 近年来,我国农业种植结构发生了很大的变化,蔬菜种植面积大幅度发展。在蔬菜栽培中,为追求生产效益菜农大量施用肥料尤其是氮肥,造成肥料利用率降低、土壤质量下降,生态环境恶化等问题。在我国经济快速发展地区,上述问题尤为严重。因而,研究该地区氮肥在蔬菜-土壤体系中的转化和去向以及对土壤质量的影响对于指导农业生产、减少农业环境污染以及促进社会经济的可持续发展具有重要意义。 本论文通过对2个蔬菜保护地的大田试验、结合3个保护地的定位监测试验以及盆栽试验,采用常规方法和示踪技术（利用无机、有机肥交叉标记）,研究常规施肥条件下有机肥氮、无机肥氮在蔬菜保护地中的转化和去向;并通过不同种植类型土壤以及不同种植年限的保护地进行土壤质量监测试验,对保护地土壤质量下降的原因进行了探索。主要结果如下: 常规田间定位试验结果表明:氮肥用量225-600 kg N·hm^-2,有机肥比例为0-100%的条件下,氮肥当季利用率小于10%。两季作物的利用率也仅有5-22%,作物未吸收的肥料氮主要以NO₃^--N和NH₄⁺-N的形态存留在剖面0-40cm土体之内,残留率为34-90%。有机肥比例较高,土壤累积的矿质氮较低,氮肥利用率较高。大田的示踪试验的结果表明:蔬菜吸收的氮素2%～11%来自于肥料,约90%的氮素是从土壤中吸收。由于受降雨的影响,化肥淋洗损失严重,总损失率高达70%。而施用有机肥增加了氮肥在土壤中的回收率。有机肥与化肥配施条件下化肥氮的土壤回收较单施化肥高,即便如此,配施条件下损失的氮素97%来自化肥氮,仅有3%来自有机肥氮。 通过对三种类型菜地,即菜稻轮作-低氮土壤、3年保护地-中氮土壤和10年保护地-高氮土壤的定点监测试验表明,随着土壤氮含量水平的提高,土壤生产力提高,蔬菜生物量和吸氮量均有明显的增加。而在三种土壤上施用相同量的氮肥后,土壤生产力随土壤肥力增加的幅度降低。在低、中氮土壤上,施肥均比对照处理增加蔬菜生物量和吸氮量,而在高氮土壤上,施肥较对照降低生物量:随着土壤肥力水平的提高,氮肥的利用率、残留率呈下降趋势,而损失率却呈上升趋势;差减法氮肥利用率为2%～14%、残留率为25%～61%、损失率为23%～72%。 盆栽试验结果表明,在氮肥用量为75～300mg·kg^-1条件下,随着氮肥用量的增加,肥料利用率降低,损失率增加。化肥较有机肥氮的当季利用率高,而残留率却低于有机肥。示踪法和差减法有一定的差异,当土壤肥力较低时,由于激发效应,施肥处理较对照吸收了更多的土壤氮素,差减法大于示踪法利用率;当土壤含有足够的氮素供植物吸收时,示踪法利用率大于差减法。 土壤质量监测试验表明,轮作类型对土壤理化性状和微生物区系有显著的影响。总体看来,保护地的微生物区系结构最不理想,盐分含量最高。相比之下,菜稻轮作对降低土壤盐分以及改善微生物区系有重要的作用。不同种植年限保护地土壤质量也有很大差异,随着蔬菜种植年限的增加,耕层土壤中EC、NO₃^--N和Olsen-P含量显著增加,土壤pH、容重显著降低。细菌和放线菌数量随种植年限呈先增加后降低的趋势,真菌却呈一直增加的趋势。初步结果表明高肥料用量导致土壤盐分增加、酸化趋势明显以及养分非均衡加剧,造成对土壤微生物和作物生长的胁迫,可能是导致土壤质量障碍的主要原因之一。更多还原

【Abstract】 [n recent years, the planting structure of agriculture has changed a lot in China. Vegetable planting area developed rapidly in a large scale. In vegetable cropping system, a great deal of nitrogen fertilizer and manure were used for the high benefit of it, which lead to the decline of nitrogen use efficiency, the degradation of soil quality and environment pollution. In Yangtze delta area, the developed region of economy in China, the intensive agriculture production with high fertilization level leads to environment pollution much more seriously. So to study the fate and transformation of nitrogen fertilizer in vegetable-soil system and the soil quality variation in this region is very important, which may give the guidance to the vegetable growers to grasp the rational application of fertilizer and as well as reduce the environmental pollution.Two field trial of greenhouse, one field orientation monitoring trail and one pot experiment were conducted to study the fate of organic nitrogen and fertilizer nitrogen in vegetable-soil system. The difference method and ¹⁵N isotope method were adopted together and the cross label technique was utilized in this study. In addition we investigated the soil quality of different type of rotation and different planting age of vegetable greenhouse cultivation. The main results as follows:The results of general field trials showed that nitrogen use efficiency less than 10% of the first vegetable crop under the follow condition nitrogen application dose 225-600 kg N·hm^-2 and the proportion of organic fertilizer between 0-100 percent. The sum of N use efficiency of two crop rotation was only 5-22%. The N remained in soil was mainly as the forms of NO₃^--N and NH₄⁺-N in 0⁴0cm depth. The apparent N recovery of soil was 34-90%. In addition, N use efficiency was improved with the manure rate of organic N/fertilizer N. The results of ¹⁵N isotope trial showed that only 2-11% of the nitrogen absorbed by vegetable was derived from fertilizer, and about 90% vegetable nitrogen came from soil. Because of the rainstorm, fertilizer nitrogen leakage was serious and about 70% fertilizer nitrogen lost. However, manure fertilization increased nitrogen recovery of soil. And fertilizer nitrogen recovery of soil was much more when fertilizer and manure employed together than that fertilizer employed only. However still about 97% of the nitrogen loss was from fertilizer and only 3% was from manure when at the mixed fertilization.Survey study was conducted on three types of vegetable field including vegetable-paddy rotation, three-year vegetable greenhouse cultivation and 10-year vegetable greenhouse cultivation, which represent low, medium and high soil nitrogen level separately. The results showed that soil productivity improved so that vegetable yield and nitrogen uptake increased with the soil nitrogen level. When the same dose of nitrogen fertilizer was used, the degree of enhancing effect in productivity declined with soil nitrogen level. In the field of the low and medium nitrogen level, vegetable yield and nitrogen uptake of fertilization treatment were all more than that of control treatment. On the contrary, in the field of high soil nitrogen level, the yield of fertilization treatment was lower than that of control treatment. The nitrogen use efficiency, N recovery rate of soil and vegetable were all decreased but nitrogen loss rate increased with soil nitrogen level. The nitrogen use更多还原