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Clay addition to light-textured soils is used to ameliorate water repellency and to increase nutrient retention. However, clay addition may also increase the potential to bind organic matter and thus C sequestration. Divalent calcium ions (Ca2+) play an important role in binding of organic matter to clay because they provide the bridge between the clay particles and organic matter which are both negatively charged. In the first experiment, quartz sand was mixed with clay isolated from a Vertosol at rates of 0, 50 and 300 g kg-1, finely ground mature wheat residues (20 g kg-1) and powdered CaSO4 at 0, 5 and 10 g kg-1. Soil respiration was measured over 28 d. Compared to the sand alone, addition of isolated clay at 300 g kg-1 increased cumulative respiration with a stronger increase than that at 50 g kg-1. Addition of CaSO4 increased electrical conductivity, decreased sodium adsorption ratio and reduced cumulative respiration. The latter can be explained by enhanced sorption of organic matter to clay via Ca2+ bridges. In a second experiment, isolated clay or subsoil of the Vertosol without or with powdered CaSO4 at 10 g kg-1 were used for a batch sorption with water-extractable organic C (WEOC) from wheat straw followed by desorption with water. Addition of 10 g kg-1 CaSO4 increased sorption and decreased desorption of WEOC in both subsoil and isolated clay. In the third experiment, subsoil of the Vertosol was used for a batch sorption in which WEOC was added repeatedly. Repeated addition of WEOC increased the concentration of sorbed C but decreased the sorbed proportion of the added WEOC. This indicates that sorption of WEOC may be underestimated if it is added only once in batch sorption experaments. 相似文献
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袁素英 《山西农业:致富科技版》2007,13(10):37-38
岢岚县是一个以农牧为主的山区小县,全县国土总面积1984平方公里总人口8.2万人,其中农业人口6.4万人,现辖2镇10乡,204个行政村.岢岚地下资源缺乏,工业基础薄弱,是全省35个国家级扶贫开发重点县之一.立足这种县情实际,近年来,县委政府把以羊为主的生态畜牧业作为强县富民的基础产业来抓,全力实施雁门关生态畜牧经济区建设,初步走出了一条自我发展、自主创新、农林牧协调推进的路子,也明鲜地提升了自己的区域特色和区域优势,尤其在新农村建设中畜牧业显得尤为重要. 相似文献
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山西省五寨县是一个资源贫乏县,除花岗岩、黏土外,有开采价值的地下资源几乎没有。但该县有广阔的土地资源,优越的水利资源,丰富的生态资源,充足的劳力资源。特别是得天独厚的沙棘资源,开发潜力大,利用价值高,是该县经济发展的潜在优势。 相似文献
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1会东县发展蚕桑茧丝产业的优势会东县栽桑养蚕历史悠久,是农村经济的传统产业。经过上个世纪80年代和90年代初两次兴桑高潮奠定了蚕业基础,初步形成了桑、蚕、茧、丝的产业格局,成为山区县域经济的拳头产业。会东县位于四川省凉山彝族自治州南端,距州府西昌市239km,距钢城攀枝花163km,是攀西资源开发区的重要组成部分。东南面金沙江环绕,全县幅员面积3216km2,总人口37万人。境内拥有丰富的地上地下资源,蕴含着巨大的开发优势和发展潜力,素有“天府之国的金边银角”之美誉。会东县气候温和,日照充足,雨量充沛,气候凉爽干燥,昼夜温差大,适宜… 相似文献
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