有机肥的碱度及其减缓土壤酸化的机制

采用元素分析法计算了我国主要有机肥种类的平均碱度，并与相关文献进行对比，讨论了有机肥碱度的影响因素及其减缓土壤酸化的机制。结果表明，不同种类的有机肥碱度范围为58.1～372.8 cmol/kg，碳酸钙当量为29.0～186.4 g/kg，其大小顺序为:谷物秸秆 豆科秸秆 绿肥 新鲜粪便 普通堆肥 高温堆肥 厩肥。有机肥的碱度与其钙含量呈极显著正相关（r =0.98, P 0.001，n =32），与其碳含量呈显著负相关（r =－0.64, P 0.001，n =32），主要取决于其中有机酸盐的当量浓度。农产品移除和有机肥投入对于农田土壤酸化是互逆的两个过程，长期有机肥投入可弥补农产品移除引起的土壤盐基矿物损失。施用碱度较高的有机肥（如高温堆肥或厩肥）可有效控制农田土壤酸化，并可节约施用成本，提高有机肥的资源利用率。

Alkalinity of organic manure and its mechanism for mitigating soil acidification

Mechanism for mitigating soil acidification in croplands were proposed on the basis of alkalinity of organic manures calculated with an element analysis method and compared with relevant reference data, and then factors affecting manure alkalinity were discussed in this paper. Results showed that the alkalinity of different organic manures ranged in 58.1–372.8 cmol/kg and the corresponding CaCO3 equivalent ranged in 29.0–186.4 g/kg. The increase of alkalinity was in the order of cereal straw < legume straw ≈ green manure ≈ fresh dung ≈ common straw compost < thermophilic straw compost ≈ barnyard manure. The alkalinity significantly positively correlated with the calcium content (r =0.98, P <0.001, n =32), but significantly negatively correlated with the carbon content (r = –0.64, P <0.001, n =32) in the organic materials, and was mainly determined by the equivalent content of organic acid salts. The output of agricultural product and input of organic manure were two inter-reciprocal processes to soil acidification in croplands. Long-term manure application could offset the loss of soil base minerals through biomass removal. Application of organic manure with high alkalinity (e.g. thermophilic straw compost or barnyard manure) not only could mitigate soil acidification in croplands, but also reduced application costs and improved the resource utilization rate of organic manure.