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Interpretive Summaries:
2008 - Effect of Organic Wastes on Ecological Security of Vegetable Soils in Zhejiang
2007 - Effects of Organic Wastes on the Ecological Security of Vegetable Soil
2006 - Effect of Organic Wastes on the Ecological Security of Vegetable Soil
2005 - Effects of Organic Wastes on the Ecological Security of Vegetable Soil
Effect of Organic Wastes on Ecological Security of Vegetable Soils in Zhejiang, 2008
Long-term and excessive fertilization of vegetable-growing soils results in P accumulation. It is urgent to develop a practical and reliable method for assessing P loss from these soils. Analysis was used to study soil P status and the relationships between agronomic and environmental soil P in order to develop an index to predict P loss in vegetable soils collected from the suburb of Hangzhou, Zhejiang Province.
Total soil P (TP) was between 0.7 to 2.9 g/kg and soil P extracted by calcium chloride (CaCl2), Olsen, and Melhich-III methods was 0.5 to 20 mg/kg, 11 to 152 mg/kg, and 50 to 905 mg/kg, respectively. About 72% of Olsen-P values exceeded the critical P level of 60 mg/kg. The degree of P saturation as measured by oxalate extraction (DPS-Ox) ranged from 7 to 49% while DPS by Mehlich-III extraction (DPS-M3) ranged from 6% to 52%. A model was used to relate soluble soil P concentrations to Olsen-P and DPS values. Soluble P loss by leaching was greater in soils with Olsen-P and DPS values that exceed 76 mg/kg Olsen-P, 25% DPS-Ox, and 22% DPS-M3. More than 60% of the soils exceeded the Olsen-P and DPS thresholds. The environmental Olsen-P threshold is above the agronomic optimum Olsen-P test value. Therefore, if soils are below these Olsen-P and DPS thresholds, then adequate crop P supply and environmental protection can both be achieved.
Chemical analysis and geographic information system (GIS) techniques were used to study the spatial distribution of soil nutrients and P leaching in 150 vegetable soils. Results found 94% of soils were below the critical levels for available N (120 mg/kg) and K (125 mg/kg), whereas 92% of soils were above the agronomic critical P level of 60 mg/kg. Great variation in soil nutrient status and spatial distribution were observed within the test area, and higher nutrient contents were found in the soils near the villages. The model used to relate soluble soil P concentrations to Olsen-P and TP, found the loss thresholds to be 78 mg/kg Olsen-P or 1.3 g/kg TP. Approximately 90% of the soils tested were above these thresholds. This project will not continue in 2009. Zhejiang-22
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