CALIBRATION OF OLSEN SOIL PHOSPHORUS TEST VALUES WITH THE PHOSPHORUS FERTILIZER REQUIREMENT OF SUGAR BEETS UNDER TURKISH SOIL AND CULTURAL CONDITIONS

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Abstract
From the results of 123 field experiments conducted in the major beet-growing areas of Turkey, the Mitscherlich-Bray calibration equation, log (100-y) = log100–0.018b1 - 0.0084 x, was obtained to represent the relationship between the percentage sugar beet yield under irrigated conditions (y) and Olsen soil test value (b1) and the amount of fertilizer phosphorus (x), both expressed in kg P2O5/ha, for a 40-cm x 25-cm planting pattern and a plowdown application of 16–18% superphosphate in late fall. The variations in soil, climate, weather, length of growing period, and maximum yield level were found not to change significantly the constants 0.018 and 0.0084 used in the equation. For the average maximum yields of 42–58 t/ha obtained in different growing areas, phosphorus fertilization aimed at practically the maximum yield was found to be economical under the current fertilizer and beet prices.
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