Effect of Long-term Lime and Potassium Applications on Quantity-Intensity (Q/I) Relationships in Sandy Soil1
- D. L. Sparks and
- W. C. Liebhardt2
The effects of long-term lime and K applications on quantity-intensity (Q/I) relationships were investigated on the Ap and B21t horizons of a Kalmia soil (a fine-loamy over sandy or sandy-skeletal, siliceous thermic (Typic Hapludults) from the Delaware Coastal Plain. The predominant mineral suite of the <2µm clay fraction was mica, vermiculite, and chloritized vermiculite. Soil pH and exchangeable bases increased with depth and with lime additions. The equilibrium potassium activity ratio (ARke) decreased with profile depth due to greater K fixation by specific sites for K in the B21t horizon. The ARke decreased in the Ap horizon and increased in the B21t horizon with lime additions. The magnitude of ARke [> 0.01 (moles/liter)½] suggests that K adsorption in the Ap horizon occurred on planar positions while adsorption at specific sites was predominant in the B21t horizon [> 0.006 (moles/liter)½]. The parameter δKo, which measures labile K, became more negative with increased lime and K additions, indicating a greater K release into soil solution. While the quantity of K extracted by NH4OAc compared favorably to δKo in the Ap horizon, it exceeded δKo in the B21t horizon, suggesting K exchange involving specific sites in the B21t horizon. The number of specific sites (Kx) increased with K fertilization and with soil depth. The decreased Kx with increased lime additions could be ascribed to increased neutralization of hydroxyaluminum interlayer material, resulting in an increase in interlayer “islands.” The potential buffer capacity (PBCk) parameter increased with lime additions due to increased pH-dependent cation exchange capacity (CEC).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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