水稻土的酸化特征及其起因

以浙江省为例,探讨了水稻土的酸化特征,并通过定点观察研讨了该省水稻土的酸化速率和酸化原因。结果表明:浙江全省水稻土pH值主要在4.50~6.50之间,以酸性为主,pH值中值为5.70;与第二次土壤普查结果相比,目前水稻土呈现明显的酸化:pH值在5.5以下的土壤比例明显地增加,而pH值在5.5~7.5之间土壤的比例明显地下降,pH值中值下降了0.39个单位。定点调查表明,近30年内水稻土的pH值下降量在0.17~0.83之间,下降速率表现为蔬菜地>桑园地>苗木地。分析认为,氮肥施用量的增加、长期旱作及大气酸沉降是引起水稻土酸化的主要原因;与其它土地利用方式相比,长期种植水稻可减缓土壤的酸化。

Characteristics and Causes of Acidification of Paddy Soil

Taking Zhejiang province as an example, the author explored the characteristics of paddy soil acidification, and studied the rate and causes of paddy soil acidification in this province through fixed -point observation. The results indicated that soil pH - vdlues varied mainly from 4.50 to 6.50, with the middle value of 5.70. Most paddy soils were acidic. The paddy soil in Zhejiang province was significantly acidified in the past thirty years, and the proportion of soils with the pH - value of less than 5.5 obviously increased, while that of soils with pH 5.5 -7.5 markedly decreased as compared with those obtained in 1980s. The mid- dle vale of soil pH - value decreased by 0.39 unit from 1980s to 2008. The results of fixed - point observation showed that the de- cline of pH - value of paddy soil ranged from 0.17 to 0.83 unit in the past 30 years. The acidification rate revealed the following or- der： vegetable land 〉 mulberry garden land 〉 nursery garden land. The acidification of paddy soil was maybe caused by the in- crease of nitrogen fertilizer application, long - term cultivation of upland crops, and atmospheric acid deposition. The long - term planting of rice can retard the acidification of paddy soil.