Abstract:

High multiple cropping index and long-term application of pesticides and fertilizers in vegetable fields have resulted in issues such as soil heavy metal pollution, soil compaction, and insufficient nutrient supply. In recent years, organic amendments, such as biochar, have been used to remediate vegetable field soils with certain achievements. In-depth research has been conducted on the systematic application of organic amendments to comprehensively remediate heavy metal pollution, improve soil fertility, and enhance the efficiency, quality, and economic benefits of the vegetable industry. A four-year (four-phase) long-term fixed-site experiment was conducted in a heavy metal-contaminated vegetable field in Guangzhou City, covering eight growing seasons (four seasons each for radish and head mustard). In each of the four phases, two organic amendments, namely biochar and humic substance, were applied. Their effects on soil heavy metal immobilization, fertility improvement, vegetable quality enhancement, and economic benefit increase were comparatively analyzed, and their soil remediation effects were comprehensively evaluated. The results indicated that after the implementation of the technology across the four phases, the key soil fertility indicators significantly improved. Compared with the control group, the application of biochar increased soil organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium by 11.1%, 38.5%, 48.4%, and 56.9%, respectively. For the application of humic substances, these parameters increased by 17.5%, 29.1%, 53.7%, and 106%, respectively, compared to the control. The content of bioavailable heavy metals in the soil decreased significantly. Compared to the control, biochar application reduced the content of bioavailable Cd and Pb by 51.2% and 47.5%, respectively. Humic substance application led to a reduction in the content of bioavailable As and Pb by 51.2% and 50.9%, respectively, compared with the control. Meanwhile, the heavy metal content in radish and head mustard decreased significantly, while the content of soluble sugar and Vc (Vitamin C) increased significantly compared to the control. In particular, under humic substance treatment, the Cd content in radish and head mustard decreased by 53.1% and 54.0%, respectively; soluble sugar increased by 25.9% and 18.5%, respectively; and Vc increased by 12.4% and 18.2%, respectively. As project duration increased, the yields of radish and head mustard under both biochar and humic substance treatments gradually increased. The calculation of the output-input ratio showed that the ratio of humic substance treatment (1.54) was higher than that of biochar treatment (1.30), which in turn was higher than that of the control (1.15). Humic substances exhibited better and more significant effects in improving vegetable field soils. The findings of this study provide a scientific basis for the use of organic amendments to remediate heavy metal-contaminated vegetable field soils and enhance soil fertility.

Key words: heavy metals, biochar, humus, soil fertility, vegetables

摘要： 菜地因复种指数高、长期施用农药化肥，易出现土壤重金属污染、质地板结及养分供应不足问题。虽生物炭等有机改良剂修复菜地土壤有一定成效，但在综合修复重金属污染、改善肥力及促进蔬菜产业增效提质方面仍缺乏系统研究。该研究在广州市某重金属污染菜地，连续4年（4个阶段）开展8季定位试验（萝卜、头菜各4季），4个阶段分别施用生物炭、木本泥炭，对比二者在重金属污染菜地上的综合改良效应。结果显示，材料施用4个阶段后，土壤肥力显著提升：与对照相比，生物炭处理土壤有机质、碱解氮、有效磷、速效钾含量分别提升11.1%、38.5%、48.4%、56.9%；木本泥炭处理分别提升17.5%、29.1%、53.7%、106%。重金属钝化效果方面，生物炭处理有效态Cd、Pb含量较对照分别下降了51.2%、47.5%；木本泥炭处理分别下降51.2%、50.9%，同时，萝卜、头菜重金属含量显著下降，可溶性糖和Vc含量显著提升，木本泥炭效果更优：其处理下萝卜、头菜Cd含量分别降53.1%、54.0%，可溶性糖含量分别升25.9%、18.5%，Vc含量分别升12.4%、18.2%。且随试验时间延长，两种改良剂处理的蔬菜产量逐步提升。投入产出比分析显示，木本泥炭处理（1.54）>生物炭处理（1.30）>对照（1.15），木本泥炭改良效应更显著。

关键词: 重金属, 生物炭, 木本泥炭, 土壤肥力, 蔬菜