不同有机肥处理对铜元素在土壤-蔬菜系统的累积及土壤形态分配的影响

Effects of Organic Fertilizer on Accumulation and Distribution of Cu in Soil-vegetable System

为探讨有机肥处理后,Cu在土壤、蔬菜中的累积及土壤Cu的形态转变规律,研究设置了不同有机肥用量处理(CK,0 t hm^(-2);T1,20 t hm^(-2);T2,40 t hm^(-2);T3,60 t hm^(-2);T4,80 t hm^(-2)),每次施用有机肥后分别种植青菜和空心菜各两茬,测定土壤、蔬菜体内Cu含量。结果表明:在不同量有机肥处理下,四茬叶菜类蔬菜收获后,土壤中Cu元素总体出现了明显累积;以每茬蔬菜种植前分别施加有机肥量20、40 t hm^(-2)为背景,根据非线性回归拟合模型,预计在第七茬和第六茬蔬菜连作后,土壤中Cu全量可能超过绿色食品环境质量标准限值;另外,Cu在叶菜类蔬菜中和土壤含量有同步累积趋势,但第四茬不同处理下蔬菜中Cu含量随着有机肥施用量的增加而明显减少,且差异显著(P <0.05)。第四茬(有机肥施用1年后)叶菜类土壤中Cu形态总体表现为残渣态>可还原态>可氧化态>醋酸提取态的规律,菜园土壤短期施用有机肥可降低土壤中的醋酸提取态占全量中的比例,减少土壤中重金属的生物有效性。在青菜和空心菜对Cu的富集系数的差异性分析中发现,空心菜对Cu的富集能力显著高于青菜(P <0.05)。四茬叶菜类蔬菜Cu总量分别与其土壤总Cu和醋酸提取态Cu含量之间存在极显著正相关关系。

In order to study the accumulation of Cu in soil and vegetable and the transformation of Cu fractions in soil after application with different amounts of organic fertilizer(CK,0 t hm^-2;T1,20 t hm^-2;T2,40 t hm^-2;T3,60 t hm^-2;T4,80 t hm^-2),two rotation crops of green vegetable and spinach respectively were planted after each application of organic fertilizer.The concentration of Cu was analyzed in soil and vegetables.The results showed that under different organic fertilizer treatments,the concentration of Cu was accumulated obviously in soil after the harvest.According to the nonlinear regression fitting model,the total concentrations of Cu in soil would exceed the environmental quality standard value of green food after the seventh and sixth successive leafy vegetable crops respectively under the background of application rates of organic fertilizer at 20 and 40 t hm^-2 before each crop of vegetable planted.In addition,there was a trend of simultaneous accumulation of Cu in leafy vegetables and soil.However,the concentration of Cu in the fourth rotation of crop vegetable was decreased significantly with the increase of application rates of organic fertilizer(P<0.05).Chemical forms of Cu in soil of the fourth rotation of leafy vegetable(after one year of continual application of organic fertilizer)were decreased in the order of residual>reducible>oxidizable>acid-extractable Cu fraction,and acid-extractable Cu was the lowest proportion of the total concentration.The short-term application of organic fertilizer reduced the proportion of acid-extractable Cu and the bioavailability of Cu in soil of vegetable garden.The accumulation capacity of Cu in spinach was significantly higher than that in green vegetables(P<0.05).By the four rotation of leafy vegetable crops,there were significantly positively correlated between the total Cu contents of vegetables and soil,and significantly positively correlated between the total Cu content of vegetables and the concentration of acetic acid extraction Cu.