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Chemical characteristics and potential source of fulvic acids leached from the plow layer of paddy soil 总被引:2,自引:0,他引:2
To understand better the chemical characteristics and source of dissolved organic matter (DOM) leached from the plow layer of rice paddies, a lysimeter study was conducted, which simulated submerged paddy topsoil during rice growth. The fulvic acid (FA) fraction in the percolation water from the lysimeter was collected by adsorption onto insoluble polyvinylpyrrolidone (PVP), and the temporal variations in its elemental composition, molecular size distribution, IR spectra, 13C CPMAS NMR spectra, and δ13C values were investigated. The proportion of the FA fraction to bulk DOM varied greatly, but the chemical characteristics of the FA fraction did not change appreciably during the experimental period. Thus, it is considered that the changes in the DOM composition in percolation water were mainly due to the differing contributions of the FA fraction. Further, to investigate the source of the FA fraction in the leachate, the chemical characteristics of the FA fraction in the leachate were compared with those extracted from the plow layer soil. A sequential extraction of the FA fraction was conducted using a sequence of water, 0.25 M Na2SO4, 0.1 M Na4P2O7 (pH 7.0), 0.1 M Na4P2O7 (pH 10.5), and NaBH4+0.1 M Na4P2O7 (pH 10.5). It was found that the water- and 0.25 M Na2SO4-extractable fractions, which were most mobile, were not the only source of the FA fraction in the leachate. The small molecular size sub-fraction of the NaBH4+0.1 M Na4P2O7 (pH 10.5)-extractable FAs, most of which are probably bound mainly to iron oxides, are considered to be another source of the FA fraction leached from the plow layer of paddy fields. 相似文献
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[目的]研究γ-聚谷氨酸增效尿素的淋溶特性及肥料效果。[方法]以制备的γ-聚谷氨酸增效尿素和常规尿素为氮肥,通过淋溶试验和盆栽试验,测定其对氮素淋失和小白菜生长的影响。[结果]淋溶试验表明,γ-聚谷氨酸增效尿素能使氮素缓慢释放,减缓氮的流失。盆栽试验显示,γ-聚谷氨酸增效尿素能显著提高小白菜的单株鲜重、单株干重和根长,分别提高了33.6%、48.4%和23.1%;能提高小白菜对氮、磷、钾营养元素的累积,小白菜的氮、磷、钾含量分别提高了16.7%、12.0%和9.9%;能提高土壤的有机质、碱解氮、有效磷、速效钾含量。[结论]γ-聚谷氨酸增效尿素的保肥效果和在小白菜上的应用效果显著,值得在小白菜种植中推广应用。 相似文献
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Hideo Nakasone 《Paddy and Water Environment》2009,7(1):65-70
Until 1997, tea farmers in the Makinohara district of Shizuoka Prefecture, Japan, applied around 1.2 ton/ha of nitrogen fertilizer
per year to their tea fields. In general, uptake amount of nitrogen by tea plants is around 300–350 kg/ha. Then some part
of the remainder of nitrogen fertilizer leach into ground water and flow out into the river. The other part of remainder of
nitrogen fertilizer is accumulated in the soil layer. Following a recommendation by the local government, this amount was
then gradually decreased to 660 kg/ha in 1999 and 540 kg/ha in 2000. Although nitrate nitrogen concentrations in local ground
and river water have decreased, they remain high today. The river water runs off from a watershed in the Makinohara area and
enters a small irrigation reservoir called Tanno Reservoir, where it has caused deterioration of the water quality, that is,
acidification of the reservoir. In Japan, environmental standard for nitrate nitrogen is 10 mg/L in public water body and
ground water. Here, the author developed the Water Quality Tank Model, and applied this model to investigate the nitrate nitrogen
concentrations in the rivers and an irrigation reservoir called Tanno. The author applies these findings to demonstrate that
nitrogen concentrations continue to remain high due to nitrogen accumulation in the soil layer, and that the amount accumulated
would be reduced by a reduction in application. The simulation results demonstrate a small decrease in accumulation in the
soil layer, and thus that the present high nitrate nitrogen concentrations will continue in ground, river and reservoir water
will decrease only gradually. 相似文献
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