Smith Matt C, White John W, Coale Frank J
USDA-ARS, Environ. Management and Byproducts Utilization Lab., Beltsville, MD 20705-2325, USA.
J Environ Qual. 2009 Feb 6;38(2):587-97. doi: 10.2134/jeq2007.0669. Print 2009 Mar-Apr.
Many states have adopted a P site index (PSI) as a risk assessment tool to determine when P-based nutrient management is required for a given agricultural field. Some PSIs use a weighting factor, the phosphorus source coefficient (PSC), to account for differences in P solubility between organic P sources. Information relating to appropriate values of PSC for various organic P sources is limited. The objectives of this study were to determine PSCs for organic P sources and to examine the relationship between PSCs and P concentrations measured in simulated rainfall runoff. An incubation study was used to calculate PSCs based on the extractability of P from organic P sources (separated and unseparated liquid dairy manure, digested dairy manure, dairy manure solids, poultry litter, and compost) relative to P from triple superphosphate fertilizer. The PSCs from the 14-d incubations were the best predictors of runoff P after 14 d soil equilibration in the runoff boxes. The values for iron-oxide strip phosphorus (FeO-P) PSC ranged from 78% for compost to 28% for poultry litter and were significantly related to runoff DR-P (r(2) = 0.80***) and FeO-P (r(2) = 0.76***) during the 14-d runoff event. Mehlich 3 PSCs ranged from 59% for compost to 30% for unseparated dairy manure and were better predictors of DR-P and FeO-P during the 56-d event (r(2) = 0.73*** and 0.65***, respectively). The results of this study indicate that PSCs based on soil incubations may improve the ability of PSCs to predict the risk of runoff transport, particularly after manure incorporation.
许多州已采用磷素位点指数（PSI）作为风险评估工具，以确定何时需要对特定农田进行基于磷的养分管理。一些PSI使用加权因子，即磷源系数（PSC），来考虑有机磷源之间磷溶解度的差异。关于各种有机磷源的PSC适宜值的相关信息有限。本研究的目的是确定有机磷源的PSC，并研究PSC与模拟降雨径流中测得的磷浓度之间的关系。采用培养研究来计算PSC，该计算基于相对于重过磷酸钙肥料中的磷，有机磷源（分离和未分离的液态奶牛粪便、消化后的奶牛粪便、奶牛粪便固体、家禽粪便和堆肥）中磷的可提取性。在径流箱中进行14天土壤平衡后，14天培养所得的PSC是径流磷的最佳预测指标。在14天的径流事件中，氧化铁条带磷（FeO-P）的PSC值范围为：堆肥为78%，家禽粪便为28%，且与径流溶解态可反应磷（DR-P）（r² = 0.80***）和FeO-P（r² = 0.76***）显著相关。Mehlich 3法的PSC值范围为：堆肥为59%，未分离的奶牛粪便为30%，在56天的事件中，它们对DR-P和FeO-P的预测性更好（分别为r² = 0.73和0.65）。本研究结果表明，基于土壤培养的PSC可能会提高PSC预测径流迁移风险的能力，尤其是在施入粪肥之后。
