Submitted to: Soil Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/1/2006
Publication Date: 4/20/2007
Citation: Brock, E.H., Ketterings, Q.M., Kleinman, P.J. 2007. Measuring and predicting the phosphorus sorption capacity of manure-amended soils. Soil Science. 172(4):266-278. Interpretive Summary: The accumulation of phosphorus in agricultural soils receiving livestock manure is recognized as a key water quality problem. As soils become increasingly saturated with respect to phosphorus, the potential for those soils to enrich runoff water with phosphorus increases. Environmental measures of a soil’s capacity to react with phosphorus provide insight into the potential for that soil to receive future applications of manure phosphorus without causing water quality concerns. However, most measures of this capacity are not offered by commercial testing laboratories. This study advances research on means of using readily-available soil testing information to estimate the capacity of a soil to react with phosphorus.
Technical Abstract: An accurate measurement of the P sorption capacity of soils is essential to understanding and managing P losses from manure amended soils. Seventeen fields were sampled from a NY farm to determine the effect of dairy (Bos taurus) and poultry (Gallus domesticus) manure application on the total phosphorus sorption capacity (PSC) and to evaluate if a single point P sorption index and readily available Mehlich-3 data can predict PSC for manure-amended soils. Three fields had no manure history, while the remainder had received solid poultry layer manure or liquid dairy cattle manure. Soils were Wellsboro or Oquaga channery silt loams ranging in total P from 1080 to 2580 parts per million (ppm) for dairy fields and 1654 to 11684 ppm for poultry fields. The PSC was poorly related to total P levels in unamended fields (r-squared = 0.42) but increased non-linearly with total P in poultry and dairy manure-amended fields (r-squared = 0.85). The PSC was well correlated to a single point P sorption index in all fields (r-squared = 0.74). The most accurate estimates of PSC were obtained using a model based on molar amounts of Mehlich-3 extractable Fe+Al and Ca (r-squared = 0.83). The degree of P saturation (DPS) was derived with this model for 126 fields of mixed manure management history. Above 32% DPS, 0.01 molar Ca-chloride extractable P increased rapidly (change point). Results of this study confirm that Mehlich-3 soil testing data can be used to predict PSC and DPS in soils with widely varying management histories.