连续施用酸化粪水对土壤养分淋溶及重金属累积的影响

为探索连续施用酸化粪水对土壤养分淋溶及重金属累积情况的影响，采用新鲜粪水和酸化粪水，开展土柱淋溶试验。试验分别设置1个对照组、新鲜粪水和3个不同pH值（6.5、6.0和5.5）的酸化粪水,每个处理分别设置6次粪水淋溶。结果表明：施用新鲜粪水和酸化粪水均能增加土壤养分，施用新鲜粪水、pH值6.5、pH值6.0和pH值5.5的粪水后土壤总养分（N、P、K）的增长幅度分别为1%～40%、15%～66%和5%～21%，重金属Cu和Zn的增长幅度为4%～48%和4%～11%，重金属Cd和Pb的增长幅度为2%～14%和1%～18%；连续施用酸化粪水会使土壤pH降低、土壤电导率值升高以及土壤重金属不断累积，这也是导致土壤环境遭到破坏的风险因素，实际应用过程中应特别注意；建议每两季作物施用一次pH值为6.5的粪水；每三季作物施用一次pH值为6.0的粪水；每四季作物施用一次pH值为5.5的粪水。该研究通过对比分析连续施用新鲜粪水和不同pH值的酸化粪水后土壤养分和重金属浓度的变化，探讨了酸化粪水的还田效果，为连续施用酸化粪水的研究提供技术支撑。

Effects of manure acidification on the soil nutrient leaching and accumulation of heavy metals in the continuous administration

This study aims to explore the effect of acid manure water on soil nutrient leaching and heavy metal accumulation in the field. Two types of fresh and acid manure water were also selected with different pH values in the experiment of continuous application. Taking the concentrated sulfuric acid as the acidifying agent, a series of indoor simulation experiments were performed on the soil column leaching. The fresh fecal water and acid septic water with three pH values (6.5, 6.0, and 5.5) were set as the control group. Six times of leaching with fecal water were then used once every 15 days in each treatment. Prior to leaching, the soil samples were taken from the different depths of soil layers (0-5 cm, 15-20 cm, and 35-40 cm) in each soil column using a syringe tube. The multi-point mixing sampling was adopted for each layer of soil. One soil sample was formed to mix evenly after drying. Each soil sample was air-dried and then bagged to store for testing. Three equal soil samples were taken from the different positions and then repeated three times for data analysis. The test results showed that there was an increase in the total soil nutrient content (N, P, and K) after the application of fresh and acidified manure water. Specifically, the fresh manure water with pH6.5, pH6.0, and pH5.5 increased by 1%-40%, 15%-66%, and 5%-21%, respectively. It was found that the total soil nutrient concentration with the application of acid manure water was higher than that of the control group. The acidification degree of the manure water increased with the amount of manure water. Furthermore, the soil heavy metals of Cu, Zn Cd, and Pb increased by 4%-48% and 4%-11%, 2%-14%, and 1%-18%, respectively. It infers that the continuous application of acidification manure water reduced the soil pH, whereas, gradually increased the soil EC value and the accumulated heavy metals in the soil. The exogenous acidulants were also introduced to change the soil sulfur element with the increase of acidification degree. As such, the risk factor was triggered to damage the soil environment during this time. Therefore, special attention should be paid to the actual application process in the field. It is very necessary to monitor the soil pH value, soil EC value, and soil heavy metal concentration every three to five years, in order to ensure that the indicators are below the critical value of risk for the better healthy growth of crops. More importantly, it is recommended to apply the manure water with the pH value of 6.5 once every two crops, or the pH value of 6.0 once every three crops, or the pH value of 5.5 once every four crops. Anyway, the soil nutrient concentration and heavy metal accumulation were compared to clarify the effect of acid manure water returning to the field, particularly after the continuous application of fresh and acid manure water with the pH values of 6.5, 6.0, and 5.5. Since the acid manure water can harm the soil after returning to the field, the finding can provide the scientific basis and technical support to the actual continuous application of acid septic water to the field.