黑土锌有效度的物理化学研究法

锌是动植物必需微量元素同时亦是污染土壤的重金属元素,研究黑土中锌形态及其有效度对保护黑土农业生态环境具有重要意义。以黑土13年长期定位试验为研究对象,采用物理化学研究法,分析评价黑土Zn形态转化及锌有效度。结果表明,长期不施肥黑土有效锌(DTPA-Zn)含量可达1.96 mg kg-1,长期施肥可显著增加黑土交换态Zn和无定型氧化铁结合态Zn含量,从而显著提高黑土有效Zn含量,可增至3.3 mg kg-1,对土壤全Zn未有明显增加;配施有机肥可显著增加矿物态Zn以外其他各形态Zn含量,土壤有效锌含量随有机肥施用量增加而逐渐增加,最高可达14.5 mg kg-1。长期施肥使土壤酸化从而降低了黑土对Zn2+的吸附强度和容量,且其吸附的Zn2+更易解吸出来,配施一定量有机肥处理虽未能减缓土壤酸化,可在一定程度上增加土壤对Zn2+的吸附强度与容量,但其吸附的Zn2+更难以解吸。总体黑土有效锌含量相对较高,对Zn2+吸附强度和容量均较高,但随着施肥引起土壤酸化而降低其对Zn2+吸附强度和容量。

Determination of Zn Availability in Black Soil with Physical-chemical Methods

Objective]Zinc(Zn)is an element essential for plants and animals,but becomes a pollutant of heavy metal element when it is too much in the soil. It is,therefore,of great significance for researchers to study forms and availability of Zn in black soil to protection of the agro-eco-environment of the black soil region,a major agricultural producing one of China. Method]Based on the data of a 13-year field experiment,designed to have 5 treatments,i.e. no fertilizer(CK),chemical fertilizer(NPK)and chemical fertilizer plus different amounts of organic manure(NPK+OM1,NPK+OM2 and NPK+OM3),in the black soil region,transformation and availability of Zn in the soil were analyzed with physical-chemical methods. Result]Results show that CK was as high as 1.96 mg kg-1 in DTPA-Zn content,Treatment NPK, increased Ex-Zn and AFeo-Zn contents,and decreased Min-Zn content,thus improving the availability of soil Zn up to 3.3 mg kg-1,but did not have much effect on total Zn. Treatments NPK+OM1,NPK+OM2 and NPK+OM3 all significantly increased all forms of Zn in content,except for Min-Zn. About 37.5%~55.5%of the input of Zn with organic manure was stored in the soil as AFeo-Zn,and the content of available Zn in the soil increased with increasing organic manure application rate and peaked up to 14.5 mg kg-1 in the field experiment In terms of Zn2+ adsorption strength and capacity,the 5 treatments displayed an order of NPK+OM2 > CK > NPK+OM3 > NPK > NPK+OM1,with Zn2+ adsorption rate and desorption rate varying in the range of 25.9%~72.1% and 4%~25.3%,respectively. Treatment NPK caused soil acidification,thus reducing the Zn2+ adsorption strength and capacity of the soil and making adsorbed Zn2+ more desorbable, while the addition of organic manure in fertilization,though unable to inhibit soil acidification,did retard the declining trend of the Zn2+ adsorption strength and capacity to some extent,and made absorbed Zn2+ harder to desorb from the soil with increasing organic manure application rate. On the whole,black soil is relatively high in available Zn content,and in Zn2+ adsorption strength and capacity,too. Long-term application of chemical fertilizers acidifies the black soil,thus transforming Min-Zn into Ex-Zn and AFeo-Zn in the soil;Zn in the applied organic manure is stored in the soil as AFeo-Zn.Conclusion]Long term application of chemical fertilizer decreases Zn2+ adsorption strength and capacity of black soil,while addition of a certain amount of organic manure in fertilization may retard the trend.