Crop Response to Single Superphosphate in Uganda Using Pot Tests

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Date
1970
Authors
Foster H. L.
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Abstract
Pot tests have been carried out on soils collected from various areas of the different regions of Uganda, where crops are known to respond to the application of single superphosphate. The results indicate that phosphate is the constituent of the fertilizer mainly responsible for crop responses, but that on very acid soils (pH less than 5.0) or on soils of very low organic matter content (around 1 per cent) calcium probably provides an extra response. The effect of the sulphur content of single superphosphate appears to be negligible. Pot and soil tests for soil phosphate deficiency are generally in agreement except for a few atypical soils where the soil test apparently extracts some phosphate which is not available to plants. Pot and soil tests for calcium are also generally in agreement though the pot tests indicate fewer deficiencies. In practical terms the results indicate that in Uganda triple superphosphate fertilizer will generally give the same results as single superphosphate. For most crops, (but possibly not Pot tests have been carried out on soils collected from various areas of the different regions of Uganda, where crops are known to respond to the application of single superphosphate. The results indicate that phosphate is the constituent of the fertilizer mainly responsible for crop responses, but that on very acid soils (pH less than 5.0) or on soils of very low organic matter content (around 1 per cent) calcium probably provides an extra response. The effect of the sulphur content of single superphosphate appears to be negligible. Pot and soil tests for soil phosphate deficiency are generally in agreement except for a few atypical soils where the soil test apparently extracts some phosphate which is not available to plants. Pot and soil tests for calcium are also generally in agreement though the pot tests indicate fewer deficiencies. In practical terms the results indicate that in Uganda triple superphosphate fertilizer will generally give the same results as single superphosphate. For most crops, (but possibly not for groundnuts which have a particularly high requirement for calcium), any "soluble" phosphate fertilizer would probably be as effective as single or triple superphosphate, except where the soil is very acid or very low in organic matter and a fertilizer which also provides calcium is required. The much quicker laboratory soil test for phosphate deficiency can generally be used to obtain the same results as the pot tests.
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East African Agricultural And Forestry Journal, XXXVI (No. 2), p. 202-206
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