【作者】 邵兴华；

【导师】 章永松； 林咸永；

【作者基本信息】 浙江大学 ， 植物营养学， 2005， 博士

【摘要】 本研究选用浙江省广泛分布的两种水稻土(红壤性水稻土和青紫泥,选择P缺乏的田块取土),研究了淹水对土壤铁氧化物转化和磷吸附-解吸行为的影响;人工合成铁氧化物磷吸附—解吸特性与磷吸附饱和度的关系;不同吸附饱和度水铁矿与水稻吸磷的关系;水稻根系泌氧作用对水稻土磷有效性和水稻磷吸收的影响;水稻根系泌氧作用和根系分泌物对固定态氮释放的影响。现将得到的一些初步结果总结如下: 1.淹水对土壤铁氧化物转化和磷吸附-解吸行为的影响 1) 土壤淹水可以显著的增加土壤中草酸可提取态铁(Feox)和草酸可提取态磷(Pox)量,草酸可提取态铁(Feox)量增加主要是以连二亚硫酸盐可溶性铁(FeocB)也就是结晶态铁氧化物的减少为代价,然而Pox/Feox比值降低了。 2) 淹水极大地增加了土壤对磷的吸附和土壤磷最大吸附量。土壤中大多数新近吸附的磷是Pox,但是还有很多新近吸持的磷不能被草酸提取出来。淹水也可以改变土壤的磷解吸特性。 3) 由于磷吸附饱和指数的降低,淹水土壤吸附的磷比不淹水土壤吸附的磷更难解吸。很显然,土壤在淹水和不淹水两种不同状态下,Feox和Pox在本质上有着显著的不同。淹水后Feox和Pox含量,磷吸附和解吸量的变化取决于不淹水土壤中的无定性和总铁氧化物的含量。我们的试验结果证实了水稻土中磷的吸附解吸行为主要是受铁氧化物形态转化的控制。 2.三种铁氧化物的磷吸附解吸特性以及与磷吸附饱和度的关系 1) 三种铁氧化物的磷吸附特性均可用Langumir方程来描述,相关系数均大于0.9,达到极显著水平。从磷最大吸附量(Qm)、吸附反应常数(K)和最大缓冲容量(MBC)三项吸附参数综合考虑,水铁矿(无定形)对磷的吸附无论在容量还是强度方面均比结晶态铁氧化物针铁矿和赤铁矿大得多。 2) 水铁矿吸附的磷比针铁矿和赤铁矿所吸附的磷更难解吸,结晶度极差的水铁矿并没有表现出大量活性表面也能为磷的释放增加表面这一作用。 3) 磷吸附饱和度有望作为评价土壤或铁氧化物磷吸附-解吸的强度和容量因子的一个综合指标。更多还原

【Abstract】 Five simulative experiments were carried out to study the effect of soil flooding on the transformation of iron oxides and the adsorption/desorption behavior of phosphate in a red earth （Ultisol） and a deglyed dark paddy soil （Entisol）, which were widely distributed in Zhejiang Province of China. Three kinds of synthetic iron oxides with different crystallinity （i.e. goethite, hematite, and ferrihydrite） were used to study the relationship between their characteristic of adsorption/desorption and phosphorus saturation. Different degree of phosphorus saturation of ferrihydrite was used to study the relationship between degree of phosphorus saturation and rice adsorbed phosphorus. The effect of the special oxidation condition in the rice rhizosphere on P dynamics, compared to the situation in the anaerobic bulk soil, and on P availability was studied. The effects of the exudation of organic acids and protons as well as their interactions on the fixation and release of ammonium in the rhizosphere was studied. The results obtained from these experiments are summarized as follows.1. The effect of soil flooding on the transformation of Fe oxides and theadsorption/desorption behavior of phosphate1) Soil flooding significantly increased oxalate-extractable Fe （Feox）, mainly at the expense of dithionite-soluble Fe （FeDCB）, as well as oxalate-extractable P（Pox）, but decreased the ratio of Pox/Feox.2) Flooding largely increased both, P adsorption and the maximum P adsorption capacity. The majority of newly sorbed P in the soils was Pox, but also more newly retained P was found to be not extractable by oxalate. Flooding also changed the characteristics of P desorption in the soils.3) Due to a decrease of the saturation index of the P sorption capacity, P adsorbed by flooded soils was much less desorbable than from non-flooded soils. There are obviously significant differences in the nature of both, the Feox and Pox fractions under non-flooded and flooded conditions. The degree of the changes in Feox, Pox, P adsorption and P desorption by flooding depended on the contents of amorphousand total Fe oxides in non-flooded soils. Our results confirm that the adsorption and desorption behavior of P in paddy soils is largely controlled by the transformation of the Fe oxides.2. Phosphorus adsorption properties of three synthetic iron oxides inrelation to phosphorus adsorption saturation1) P adsorption properties of three synthetic iron oxides could be described by Langumir equation with a correlation coefficient larger than 0.9 at 1% significant level. It was found by comparing Qm （maximum quantity of adsorption）, K （adsorption constant） and MBC （maximum buffing capacity） of three synthetic iron oxides that ferrihydrate （amorphous） was much larger than crystalline iron oxides （goethite and hematite） in both intensity and capacity of P adsorption.2) P adsorbed by ferrihydrate was much more difficult to be desorbed than those by goethite and hematite. The effect of P desorption enhanced by the large active surfaces of ferrihydrate with very poor crystallinity was not observed in the experiment.3) It was suggested by our results that P adsorption saturation may be available for use as an integrative index for estimating the intensity and capacity of P adsorption-desorption in soils or iron oxides.3. Phosphorus Adsorption Saturation of Ferrihydrate as an Index ofPhosphorus Availability to Paddy Rice （Oryza sativa L.）The results obtained from experiments showed that the artificially synthesized ferrihydrate had a very large adsorption potential to P, with 45045 μg P g^-1 of maximum adsorption capacity （Qm）. P adsorption isotherm of ferrihydrate could be fitted very well with Langmuir equation. Desorption of P adsorbed by ferrihydrate was mainly controlled by P adsorption saturation of ferrihydrate. P adsorbed by ferrihydrate with saturation less than 30% was hardly desorbed. P desorption slowly increased with the increase of P saturation from 30% to 60%, but sharply increased with P saturation larger than 60%. Th更多还原