【作者】 曹宁；

【导师】 曲东；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2003， 硕士

【摘要】 已有研究证明，水稻吸收土壤磷普遍高于肥料磷。设法增加土壤有效磷含量，是大幅度提高水稻产量的有效途径。铁是水稻土中淹水后最易引起化学行为变化的元素之一，而土壤磷的有效性在很大程度上受铁形态转化的制约，因此研究氧化铁对水稻土中磷素化学行为的影响，在提高土壤肥力方面有重要意义。 本研究选用吉林、四川、江西和广东4个不同地区水稻土为材料，采用淹水密闭恒温培养的方法，对厌氧条件下，水稻土中铁还原对磷素化学行为的影响进行了研究，旨在了解我国不同地区水稻土中氧化铁还原对磷素转化的影响特征和规律。采用盆栽育苗试验，探讨了添加氧化铁及不同有机物质对水稻生长的影响。获得以下主要结论： （1）厌氧培养可使土壤中有效磷浓度增加，4种土壤有效磷平均增幅为12.4mg／kg～50mg／kg。培养30d内，吉林土、四川土、江西土和广东土中有效磷含量与Fe（Ⅱ）浓度变化的相关性均达到极显著水平，相关系数分别为0.9679、0.9744、0.8949和0.7501。说明厌氧铁还原是磷有效性提高的重要原因。 （2）4种土壤厌氧培养30d后Fe-P均有不同程度的增加，Al-P和O-P则呈下降趋势。吉林和广东土Al-P和O-P的减少量小于Fe-P的增加量，说明有机磷矿化在无机磷形态转化中具有重要作用；四川土中，Fe-P、Al-P和O-P的总量减少，表明铁、铝形态的无机磷有向Ca-P转化的趋势。 （3）不同土壤对外源氧化铁的还原能力不同。添加氧化铁后，四川和江西土中Fe（Ⅱ）含量在培养过程中一直高于对照；广东土中Fe（Ⅱ）含量在培养40天内基本与对照持平，40天后逐渐高于对照；而吉林土中氧化铁还原有明显的滞后现象。 （4）添加氧化铁可使土壤中有效磷浓度降低，说明氧化铁对土壤磷素有固定作用。在培养的前30天，江西土和广东土的有效磷含量低于对照，30天后与对照相同，表明在还原条件下，被氧化铁固定的磷又可缓慢释放出来成为有效态。 （5）土壤添加PO₄^3-后有效磷浓度有明显增加，而添加PO₄^3-及氧化铁后土壤有效磷浓度均出现降低的趋势（相比对照），说明加入的PO₄^3-被氧化铁大量固定。 （6）加入磷酸盐后4种土壤中Fe-P、Al-P、O-P均有不同程度的增加，其中Fe-P的增幅范围为0.51mg／kg-141.61mg／kg，且江西土＞广东土＞吉林土＞四川土；Al-P的平均增幅为11.87mg／kg-26.73mg／kg，O-P增加量大小顺序为广东土＞四川土＞江西土＞吉林土；加PO₄^3-及氧化铁前后，4种土壤Al-P的变化量减少而O-P的变化量增加，表明氧化铁促进了磷酸盐向O-P形态转化，并抑制了Al-P的生成。 （7）添加EDTA和黄腐酸可使土壤有效磷有大幅度的增加。由于EDTA和黄腐酸对氧化铁的络合及溶解作用，促进了土壤中微生物铁还原过程，导致土壤有效磷浓度的增加。 （8）土壤中添加无定形氧化铁，对水稻茎叶、根系干重以及总生物量都有影响，表现为低浓度水平的添加量促进水稻茎叶、根系及生物量的增长，高水平的添加量则会产生抑制作用。本实验中，促进和抑制的浓度转折点是50 omolFe/g土。 （9）添加EDTA、黄腐酸及醋酸盐的盆栽试验表明，20，mol怡干土的EDTA可使水稻地上部分生长受到严重抑制，添加黄腐酸后水稻生物量小于对照，而添加醋酸盐处理对水稻生物量有一定促进作用。更多还原

【Abstract】 Incubation method and pot experiments were carried out to study the characteristics that effects of reduction of iron oxides on phosphorus availability. The paddy soil samples were collected from the paddy fields in four province and regions: Jilin, Sichuan, Jiangxi and Guangdong. The primary results were as follows:(1) The concentration of available phosphate of the soils increased significantly with the increasing of Fe(II) during the anoxic incubating process. Under anaerobic condition for 30 days, there are distinct linear correlative relations between Fe(II) and available phosphate. The correlation coefficients of four simples reach the upmost distinct level. It shows that the reduction of iron oxides should be an important factor affecting P availability in paddy soil.(2) Under anaerobic condition for 30 days, the content of Fe-P increased with the decreasing of Al-P and O-P. The reduction of Al-P and O-P were less than the increase in Fe-P in Jilin and Guangdong slurries. It shows that mineralization of organic phosphorus may affect the transformation of inorganic phosphorus. In Sichuan slurries, the total content of Fe-P, Al-P and O-P have decreased. The result indicated that anaerobic condition enhanced the transformation of Fe-P, Al-P and O-P into Ca-P.(3) The reductions of additional ferrihydrite were different in different slurries. The contents of Fe(II) by addition of ferrihydrite are higher than CK in Sichuan and Jiangxi soils, but they are have equal amounts in Guangdong soils under anaerobic condition for 40 days. The process of Iron reduction was more slowly in Jilin paddy than that in other paddy slurries.(4) Addition of iron oxides may decrease the availability of phosphorus. The result shows that iron oxides could fix phosphate, but much of the fixed phosphate could be released during anaerobic incubation process.(5) The concentrations of available phosphate increased by addition of PO43- in paddy soils, but they decreased by addition of PO43- and ferrihydrite. It shows that the additional PO43- may be fixed by ferrihydrite.(6) Addition of PO43- may increase the content of Fe-P, Al-P and O-P in paddy soils. The content of Fe-P increased by 0.51mg/kg-141.61mg/kg, and Jiangxi soil >Guangdong soil >Jilin soil>Sichuan soil. The content of Al-P increased by 11.87 mg/kg-26.73mgkg. The order of O-P is Guangdong soil >Sichuan soil >Jiangxi soil > Jilin soil. Before and after addition of PO43- and ferrihydrite, the variety of Al-P increase and O-P decrease. It means thatferrihydrite enhance the transformation of PO4-3 into O-P, but repress PO43- translate into Al-P.(7) EDTA and fulvic acid may increase available phosphate concentration by advanced the reduction of iron oxides in paddy slurries.(8) Addition of ferrihydrite into paddy slurries may affect the biomass of rice. The content of additional ferrihydrite had notable effects on rice growth. If the lever of ferrihydrite is higher than 50 umol/g in soil, it will inhibit the growth of rice.(9) The pot experiments of addition of EDTA , fulvic acid and acetate shows that 20 u mol/g EDTA may inhibit the growth of upground of rice. The biomass of rice by fulvic acid addition, but additional acetate may promote the growth of rice.更多还原