西苕溪流域菜地土壤肥力状况与磷素流失风险

Fertility status and phosphorus loss risk of vegetable field soils in Xitiaoxi watershed

菜地土壤集约化利用程度高,容易出现养分不平衡和过量积累等问题,严重影响蔬菜产业的可持续发展。本文基于西苕溪流域露地和设施栽培模式下菜地土壤肥力状况和主要障碍因子分析,探究了菜地土壤磷素流失风险阈值。结果表明:露地菜地土壤pH值显著低于设施菜地(P<0.05);设施菜地土壤全钾、速效钾、有效磷、水溶性磷含量和水溶性盐总量、电导率显著高于露地菜地(P<0.05)。2种栽培模式下95.8%菜地土壤处于Ⅱ级肥力水平。土壤水溶性磷与Mehlich 3-P的关系可用分段线性回归方程表征,估算得出露地和设施菜地土壤磷素流失风险阈值分别为102.7、128.7 mg/kg,超过对应阈值的样本数分别占总数的65.0%和83.3%。综上所述,西苕溪流域内露地和设施菜地土壤酸化状况较为严重,磷素潜在流失风险非常高,其中设施菜地土壤次生盐渍化问题更为突出。

The high degree of intensive utilization of vegetable field soils is prone to nutrient imbalance and excessive accumulation, which hinders the sustainable development of vegetable production. Based on the analysis of fertility status and main obstacle factors of vegetable field soils under the open land and facility cultivation patterns in the Xitiaoxi watershed, the threshold of soil phosphorus(P) loss was explored in this study.The results indicated that the soil pH value under the open land cultivation pattern was significantly lower(P<0.05) than that under the facility cultivation pattern. The contents of soil total potassium(K), available K,available P, and water-extractable P under the facility cultivation pattern were significantly higher(P<0.05) than those under the open land cultivation pattern, as well as the total soluble salt content and electrical conductivity. It was also found that the fertility grades of vegetable field soils under the two cultivation patterns were mostly(95.8%) Grade Ⅱ. The correlation between soil water-extractable P and Mehlich 3-P was well illustrated with the piecewise linear regression equation. The threshold of Mehlich 3-P for controlling P loss from the open land and facility vegetable field soils was estimated to be 102.7 mg/kg and 128.7 mg/kg, respectively. Thus, the soil samples exceeding this threshold accounted for 65.0% and 83.3% of the total number of samples, respectively. In conclusion, the soil acidification and the risk of P loss under the open land and facility cultivation patterns in the Xitiaoxi watershed are serious, and the soil salinization under the facility cultivation pattern is an outstanding issue.