Phosphorus retention in Indiana soils
Abstract
Concerns about phosphorus (P) inputs to sufacewaters from agriculture have brought renewed interest in the P retention dynamics of surface and subsurface soils. Laboratory studies were conducted on 19 Indiana soil series (87 total horizons) to determine (1) P sorption capacities, (2) P retained at equilibrium solution concentrations (ESC) of 0.10, 0.25, 0.50, 1.0, and 2.0 mg P L$\sp{-1}$, and (3) physical and chemical properties associated with soil P retention. Phosphorus sorption capacities ranged from 80 to 425 mg P kg$\sp{-1}$. Phosphorus retained at each ESC in the upper two horizons was negatively correlated with oxalate extractable P (P$\sb{\rm ox}$)/oxalate extractable (Al (Al$\sb{\rm ox})$ + Fe (Fe$\sb{\rm ox}$)) (PSI). Phosphorus retained at each ESC for the lower horizons was positively correlated with dithionite extractable Al and negatively correlated with organic carbon (C$\sb{\rm org}$), Bray P$\sb1$, and P$\rm\sb{ox}/Al\sb{ox}$. Soil Bray P$\sb1$ following P addition and one-year incubation could be predicted with initial Bray P$\sb1$, initial PAlF, and exchangeable Ca (Ca$\sb{\rm ex}$) (r = 0.978, P $<$ 0.001). The PSI was the only soil property to adequately predict WSP concentrations in the first extract following the one-year incubation. Regression analysis indicates that WSP levels will exceed 0.10 mg P L$\sp{-1}$ when PSI values exceed 0.147. The Bray P$\sb1$ soil test was also the best single parameter for predicting cumulative water-soluble P (CWSP) in non-calcareous horizons (R = 0.885, P $<$ 0.001). A Bray P$\sb1$ soil test of 39.7 mg P kg$\sp{-1}$ was required for the presence of water-soluble P. Regression analysis indicated that 65.5% of Bray P1 extractable P above a Bray P$\sb1$ of 39.7 mg P kg$\sp{-1}$ is potentially water-soluble. Adding C$\sb{\rm org}$ and Ca$\sb{\rm ex}$ improved the correlation coefficient for the CWSP regression equation (R = 0.938, P $<$ 0.001). The results of this laboratory research show that common soil test information can accurately predict CWSP for Indiana soils.
Degree
Ph.D.
Advisors
Joern, Purdue University.
Subject Area
Soil sciences|Environmental science|Agricultural chemicals
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