| Abstrakt: |
It is important to determine if and to what extent P moves through some acid sandy soils and, in view of the high cost of fertilizer P and the problems associated with pollution of ground water, what can be done to prevent or reduce the movement when it occurs. Segmented columns, 25 cm in length and 5 cm in diam., were used to study P leaching in five mineral and one organic soil. A total of 25 or 50 cm H2O was passed through the columns, containing soil from various depths, after treatment in the top 2 cm with 0 to 600 ppm P tagged with 32P. Phosphorus and other ions were measured in the leachates and at the end of the leaching period in 5 cm segments of the soil columns. For those soils where leaching of P occurred, lime effects on its reduction were investigated by repeating the experiment with the addition of Ca(OH)2at rates to supply 0 to 800 ppm Ca in the soil. Movement of P from the column was nil in Red Bay fine sandy loam but occurred for the other soils as follows: Leon fine sand > Oldsmar fine sand > Eustis loamy fine sand > Lakeland fine sand > Tomoka muck. Leaching was positively related to rates of applied P and negatively related to rates of applied P and to the level of organic matter, Fe and Al contents, pH, and rate of liming. The degree to which these factors affected leaching varied with the soil as well as the location in the profile from which the sample was collected. Leaching of K, Ca, and Mg occurred in all soils. The amount was generally related to the CEC or the levels present in the extractable form before the leaching began. Leaching of Fe and Al was determined only on soils where P leaching was appreciable. These ions generally leached with P but there was a direct relationship between leached and 0.1 NHC1 extractable ions. These data are of value in evaluating and determining P and lime requirements. |
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