长期秸秆还田和地下水位对土壤镉积累及有效性的影响

Effect of long-term straw returning and groundwater level on cadmium accumulation and availability in soils

以1982年开始的长期定位试验为对象,研究了2个地下水位(高水位-20 cm和低水位-80 cm)下3种施肥方式(高量秸秆还田HS、常量秸秆还田MS、化肥CF)对水稻土镉积累及有效性的影响。结果表明:高水位条件下,长期秸秆还田可增加土壤总镉及有效态镉含量,HS和MS处理分别较CF处理提高21.8%、59.9%和9.8%、49.2%。低水位条件下,HS处理土壤总镉及有效态镉含量高于CF处理,较CF处理分别提高11.2%和31.6%;MS处理土壤总镉及有效态镉含量低于CF处理,较CF处理分别下降8.8%和14.3%。2012年,在保证原定位试验有足够重复的前提下,变更高水位条件下的部分试验处理。当HS处理变更为CF处理5 a后,土壤总镉和有效态镉含量分别较变更前下降2.5%和5.7%;CF处理变更为MS处理后,土壤总镉和有效态镉含量分别较变更前增加16.5%和58.9%。相同施肥处理,高水位土壤总镉含量高于低水位土壤。在MS处理下,高水位土壤有效态镉含量也高于低水位土壤,而在HS和CF处理下,低水位土壤有效态镉含量高于高水位土壤。土壤镉含量和土壤基本理化性质的相关分析表明,土壤总镉与土壤有机质、络合态铁含量极显著正相关,与pH显著负相关;土壤有效态镉与土壤pH、游离氧化铁极显著负相关。研究表明,施肥方式和地下水位是通过改变土壤的基本性质影响土壤镉的积累及其有效形态。

This study was carried out to better understand the effects of fertilization methods on Cd accumulation and availability in paddy soil in a long-term experiment that began in 1982.Three fertilization methods were investigated—high amount of straw returning(HS),normal amount of straw returning(MS),and chemical fertilizer(CF)—at two groundwater levels—high water level(-20 cm)and low water level(-80 cm).The results showed that,under high water level,long-term straw returning increased the content of total and available Cd in soils.In comparison to CF treatment,HS and MS treatments increased the content of total and available Cd in soils by 21.8%and 59.9%,and 9.8%and 49.2%,respectively.Under low water level,HS treatment had a higher content of total and available Cd than CF treatment and increased them by 11.2%and 31.6%,respectively.MS treatment had a lower content of total and available Cd than CF treatment and decreased them by 8.8%and 14.3%,respectively.In 2012,given the premise of sufficient repetition of the original positioning test,part of the test treatment under the high water level condition was changed.After 5 years of changing HS treatment to CF treatment,the content of total and available Cd in soil decreased by 2.5%and 5.7%,respectively;CF treatment was then changed to MS treatment,resulting in an increase in the content of total and available Cd in the soil by 16.5%and 58.9%,respectively.Under the same fertilization treatment,the total Cd content in the high water level was higher than that in the low water level condition.MS treatment caused the available Cd content in the high water level to be higher than that in the low water level condition,while HS and CF treatments caused the available Cd content in the low water level to be higher than that in the high water level condition.Correlation analysis of soil Cd content and the basic physical and chemical properties of the soil showed that the total Cd content in the soil had a significant positive correlation with soil organic matter,while complex iron content had a significant negative correlation with pH value.The available Cd in the soil had a significant negative correlation with soil pH value and free iron oxide.Fertilization and water levels affected the accumulation and chemical speciation of Cd in soil by changing the basic properties of the soil.