植物残茬对土壤酸度的影响及其作用机理  

Effect of plant residues on soil acidity and its mechanisms

作　　者：李志安[1] 邹碧[1] 丁永祯[1] 谭万能[1] 夏汉平[1] 沈承德[2] 孙彦敏[2] 

机构地区：[1]中国科学院华南植物园,广州市乐意居510650 [2]中国科学院广州地球化学研究所,广州市510640

出　　处：《生态学报》2005年第9期2382-2388,共7页Acta Ecologica Sinica

基　　金：国家自然科学基金资助项目(30170191);中国科学院方向性资助项目(KSCX2-SW-133);广东省自然科学基金资助项目(5006760);华南植物研究所所长基金资助项目~~

摘　　要：土壤强酸性是作物生长的最主要限制因子之一,某些植物残茬可以有效地提高土壤pH,降低活性铝含量,提高作物产量。植物残茬改良土壤酸度的效能因种而异,最高土壤pH升幅可达4.53个单位,多种豆科植物材料可使土壤pH提高2个单位以上,当pH>5时,土壤溶液活性铝降至极低水平,从而消除铝害。植物残茬改良土壤酸度的效能受植物残茬自身特性与土壤特性的影响,而且pH的上升通常在几个月后消失,但这种效能对当季作物有效。植物体内有机酸根的去羧化作用被认为是pH上升的主要机理之一,去羧化机理存在的主要证据是,随着土壤pH升高,植物材料内的可溶性有机成分下降,CO2排放与pH上升高度相关,以及杀菌条件下土壤pH上升速度显著减慢。超量碱机理是植物残茬导致pH上升的又一可能的重要机理,亦即有机盐的作用,有机盐分解转化为碳酸盐,其作用与石灰完全相似,有机盐水解也可导致土壤溶液的碱性反应。铵化作用与硝化作用是高氮植物材料影响土壤酸度的重要机理,有机氮的铵化直接消耗质子,铵的硝化则产生质子,pH的变化与这些氮过程高度相关。含硫植物材料及有机物质分解过程产生的氧化还原条件的变化,也可对土壤pH产生影响,但它们的作用较小。综合来看,去羧化作用机理基于间接证据,没有得到严格验证,超量碱机理可能是土壤pH上升的主要原因,超量碱只能转移,不能制造,含超量碱高的外源性有机材料施入耕地,将是改良土壤酸度,提高作物产量的一种有效途径。Low soil acidity is one of the most important constraints for crop growth in high rainfall area. Some plant residues could efficiently increase soil pH and reduce Al activity of soil solution, leading to better crop production. The potential of plant residues to ameliorate soil acidity varies greatly, depending on both the nature of plant residue and the type of soil. Highest pH increase reported was 4.53 pH units. Several legume materials could increase soil pH by more than 2 units. When soil pH increases to higher than 5.0. Al concentration in soil solution drops to very low level and poses no more threat to crop growth. The soil pH increase by plant residues benefits crop production although such effect often lasts for onlya few months. Decarboxylation of organic anions in plant residues is often regarded to be a main mechanism for pH increase. Several facts support this hypothesis： Soluble organic carbon was observed to decrease with increasing soil pH. Significant correlation was found between pH increase and CO2 release, which reflected the decomposition process of organic materials. Soil pH increased much more slowly in sterile treatment than non-sterile treatment. Excess base or ash alkalinity, namely the effect of organic salts, is also proposed to be a main mechanism for soil pH increase. Decomposition of organic materials converted organic salts into carbonates, which had similar effect on soil to lime. Hydrolysis of the organic salts also results in alkaline reaction in soil. Ammonification and nitrification play important roles in soil pH change for the plant materials containing high nitrogen. The ammonification consumes protons and the nitrification produces protons, governing pH changes in soil. Oxidation of organic sulfur and oxidation/reduction of Mn also contribute to pH change, but to a limited extent. As a whole, the decarboxylation largely relies on indirect evidence and is not rigorously tested yet. Excess base is the most likely factor to increase soil pH as a result of addition of organ

关 键 词：酸性土 去羧化 超量碱 植物残茬 土壤改良 

分 类 号：S153.4[农业科学—土壤学]