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The fate of phosphorus applied as superphosphate and rock phosphate to grassland plots at Kybybolite established in 1919 on solonetzic soils has been studied by soil analytical techniques. The additional effect of the amendments lime and gypsum has also been examined. From past records of phosphorus added as fertilizer, the probable amounts of phosphorus removed in animal products, and present phosphorus levels of the surface 8 in. of soil, it has been possible to draw up a balance sheet of gains and losses. The results show that considerable penetration of phosphorus applied in the water-soluble form has occurred. Less than half the phosphorus applied as superphosphate can be accounted for in the surface 8 in. The remainder is presumed to have been leached to lower soil horizons. In contrasting these results with those of other areas of similar rainfall where little movement of applied water-soluble phosphate has occurred, it is believed that the greater penetration at Kybybolite can be explained on the basis of the coarse texture and the low fixing capacity of the surface soil. Where acid-soluble phosphate has been applied, less movement through the soil is apparent, and 75 |
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