【作者】 赵洁丽；

【导师】 胡锋； 刘勤； 张斌；

【作者基本信息】 南京农业大学 ， 土壤学， 2007， 硕士

【摘要】 花生是南方红壤区主要经济作物之一。近年来由于化肥的大量投入，致使该区花生根系结瘤量大幅度减少甚至出现零结瘤现象，生物固氮能力急剧降低。而化肥的过量使用不仅导致了肥料利用率的下降，同时还带来了农业面源污染等一系列的后续环境问题。因此，研究怎样通过恢复花生自身的固氮能力以减少化肥氮的投入也就成为该区亟待解决的问题。本研究选择了红壤区典型种植模式（夏花生-冬蔬菜、夏花生-冬休闲）下的两种不同土壤N素背景值（高、中）花生地为供试土壤，通过两年的田间试验研究了不同施氮水平下花生根系结瘤能力、根系固氮能力、根系形态学特征、植株各部干物质累积量、叶片SPAD值以及氮素吸收利用规律。同时，为了达到通过平衡施肥，恢复土壤生态功能的目的，本试验还研究了施用根瘤菌肥料和硼、钼两种微量元素肥料对花生根系结瘤、根瘤发育、根系形态学特征以及植株干物质累积量的影响。试验结果表明：1)花生生物固氮功能受外源无机氮投入量的影响。当土壤N素背景值较高时，花生根系固氮酶活性与施氮量呈极显著（p=0.005）的负相关关系(R²=0.88^**)，花生单株根系结瘤数和单株根瘤干物质重也随着氮肥施用量的增加而显著下降。土壤N素背景值为中等时，施入少量氮肥对生物固氮表现为促进作用；当施氮量大于一定数值后就表现为强烈的抑制作用。2)花生根系形态学特征对外源无机氮的输入反应敏感。当土壤N素背景值较高时，输入无机态氮后根系向短粗方向发展。单株花生根系总长度、总表面积、总分叉数及总根尖条数均随氮肥施用量的增加而减小，根平均直径呈增大趋势。当土壤N素背景值为中等时，适量施氮可促进根系发育，主要表现为根系总长度、总表面积、总体积及总分叉数以及总根尖条数的增加。继续提高施氮量时，以上指标均表现出一定程度的减小。3)土壤N素背景值较高时，施用氮肥对花生荚果产量、茎秆产量以及植株总生物量的影响均不显著（p=0.091）。而土壤N素背景值为中等时，少量施氮可提高花生荚果产量和植株各部干物质累积量；提高氮肥用量后，荚果产量及植株各部干物质累积量均呈现下降趋势。花生叶片SPAD值变化与荚果产量变化趋势一致。4)花生氮素利用规律在两种土壤N素背景值下表现趋势一致。均表现为：随着外源无机氮输入量的增加，氮素回收率（RE）与氮素农学利用率（AE）显著降低，而收获指数（HI）及氮素内部分配效率（IE）未得到相应提高。5)N¹⁵示踪试验结果中，中等土壤N素背景值条件下，花生植株对肥料N的摄取百分数在23.99％～38.37％之间，其数值随施氮量的提高而降低；花生生物固氮量在52.58 kg·hm^-2～30.64 kg·hm^-2之间，其值随施氮量的提高先缓慢增加后迅速下降；花生植株对土壤中N的摄取量在46.37kg·hm^-2左右，提高施氮量其值变化不大。6)施用根瘤菌肥料对单株花生结瘤量、根瘤干物质重、根系固氮酶活性、根系形态特征以及花生荚果产量、生物量的影响均达不到显著水平。7)微量肥料硼、钼配施可促进根瘤的发生和发育，表现为根系结瘤量和根瘤干物质重的明显增加，同时荚果产量及主要经济性状指标也有积极响应。而硼、钼单独施用时，其效果与对照间差异不显著。更多还原

【Abstract】 Peanut is one of the main economic crops in red soil area, southern part of China. Inrecent years, nodule biomass and biological nitrogen fixation of peanut reducedsignificantly （some even to disappear）, the reason for which is overuse nitrogen fertilizer inpeanut field. Overuse of nitrogen not only led to lower nitrogen use efficiency, but alsocaused a series of environmental problems like non-point pollution source from farmland.Therefore, how to cut down the application rate of chemical N by the way of promotingbiological nitrogen fixing of peanut is becoming a key issue to be solved.A field experiment was carried out on typical red soil upland, which was aimed tostudy the responses of nodule biomass, biological nitrogen fixation, root morphologicalproperties, plant biomass, SPAD value and nitrogen use efficiency under different levels ofchemical N application. Two separated peanut fields were found to serve as comparison forabove experiment. The first field is of higher indigenous N supply with a cropping systemof summer peanut-winter vegetable and the second is of lower indigenous N supply with acropping system of summer peanut-winter follow. Meanwhile, additional experiments wereconducted to see how nitragin fertilizer and microelement B, Mo will affect nodule biomass,root morphology and plant biomass of peanut.The results are as follows:1). In the first feild, biological nitrogen fixation was influenced by the levels ofchemical nitrogen application. Special acetylene reduction was negatively correlated to theapplication rate of chemical nitrogen (R²=0.88^**,p=0.005). Nodule dry matter and nodulenumber per plant decreased when higher levels of nitrogen were applied. In the secondfield, biological nitrogen fixation was promoted when very low level of nitrogen wasapplied. However, it decreased significantly when a certain level N was added.2). Root morphological properties responded sensitively to the applied N level. In thefirst field, the analyses of root morphology showed that the properties, including Total Length （TL） and Total Surface Area （TSA） and Total Forks Number （TFN） and Total TipsNumber （TIN）, decreased significantly when a higher level of nitrogen was applied. But inthe second field, morphological properties were promoted when a low level of N wasapplied, but they would decrease under higher levels of N condition.3). In the first field, application of N contributed little in promoting peanut yield,above-ground biomass and total biomass （p=0.091）. In the second field, very low level of Nwas needed in maintaining peanut yield. Overuse of N seemed to reduce peanut yield.4). Nitrogen use efficiency showed similar trends in both fields. Nitrogen recoveryefficiency （RE） and Agronomic efficiency （AE） showed a negative trend to the amount ofapplied N. Internal efficiency （IE） and harvest index （HI） did not respond significantly tothe amount of applied N.5). In the second field, results of N¹⁵ fertilizer tracer contents showed that theproportion of absorbed N from fertilizer were varying from 23.99% to 38.37%, which wasnegatively correlated to chemical N application rate. Biological fixed N by peanut wasvarying from 52.58 to 30.64 kg ha^-1. Biological nitrogen fixation rate was promoted when alow level of nitrogen was applied. However, it decreased significantly when a certain levelof N was added. The amount of absorbed N from soil was about 46.37 kg ha^-1, nosignificant differences were found between fertilizer treatments.6). Application of nitragin fertilizer did not significantly improve the properties suchas nodule biomass, Nitrogenase activity, root morphology, plant biomass and yield ofpeanut.7). Combination of microelement fertilizers （boron and molybdenum） promoted thenumbers and biomass of root nodules, which contributed positively the yield of peanuts andsome other economic indices. No significant differences were found when singlemicroelement fertilizer was applied or not.更多还原