黄土高原旱地连续施用锰肥的土壤效应研究

EFFECTS OF CONTINUOUS APPLICATION OF MANGANESE FERTILIZER ON MANGANESE BEHAVIOR IN DRYLAND SOILS OF THE LOESS PLATEAU

采用连续浸提形态分级方法，研究了连续施用锰肥17a后锰的土壤化学特性变化。结果表明：经过长期连续施用锰肥，土壤全锰和DTPA—Mn含量增加不多。土壤DTPA—Mn含量随试验时间的延长呈增加趋势，施锰土壤有效锰提高不多，土壤DTPA—Mn含量只增加了0．4～1．7mgkg^-1。土壤中的锰主要以矿物态存在，占土壤全锰含量的比例为87．3％～91.8％。碳酸盐态、氧化锰态和紧结有机态锰占全锰的比例相当，土壤中各形态锰按含量大致呈矿物态〉碳酸盐态〉氧化锰态〉紧结有机态〉松结有机态〉交换态的顺序。施入土壤的锰肥有91．1％～98．6％进入碳酸盐结合态、氧化锰结合态、紧结有机态和矿物态，只有很少一部分仍留在有效态锰库中。交换态和松结有机态锰对土壤锰的有效性起着主要作用，可以反映土壤锰的供给状况，碳酸盐态和紧结有机态锰不能反映土壤锰的有效性。

Manganese deficiency has been a problem in agricultural practice in many soils in North China and manganese fertilizer also has been extensively used to correct the problem. In order to further understand behavior of manganese fertilizer in soils, a long-term field experiment was initiated in 1984 on continuous application of manganese fertilizer in dryland soils of the Loess Plateau. After 17 years, availability and fractions of manganese in the soil were investigated using a modified sequential extraction technique. The results showed that total manganese and DTPA extractable manganese were not increased much in the soil. But the latter did show an increasing trend with the time, no matter manganese fertilizer was added or not. In addition, the application of manganese fertilizer contributed little to increase of soil DTPA-Mn, which ranged from 0.4 to 1.7 mg kg^-1. Manganese fractions in all studied soils were greater in manganese fertilizer treatments compared with those in control. It was also found that mineral bonded manganese occupied about 87.3 % ～ 91.8% of the total soil manganese, while carbonate form and oxides form of manganese, and organic matter strongly bonded manganese shared similar percentages. In terms of content, the various fractions of manganese ranked in the order of mineral bonded 〉 carbonate bonded 〉 oxides bonded 〉 organic matter strongly bonded 〉 organic matter weakly bonded 〉 exchangeable. About 91.1% -98.6% of fertilizer manganese was in the form of carbonate bonded, oxide bonded, or organic matter strongly bonded manganese, or in the mineral form, which were not readily available for the crop to use. Only 1.4% - 8.8% of fertilizer manganese entered into exchangeable and organic matter weakly bonded forms, which were considered as available manganese in soils. The results of statistical analysis showed that exchangeable and organic matter weakly bonded manganese were the major sources of soil available manganese, carbonate bonded and organic matter strongly bonded manganese made little contribution to soil available manganese.