Experiments on the effects of phosphate applied to a Buganda soil: II. Field experiments on the response curve to triple superphosphate

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Abstract
SUMMARY A sigmoid curve for response to superphosphate has been demonstrated in field experiments in a Buganda red clay loam. There was evidence that the curve was abnormal; with small dressings of triple superphosphate yield of cotton and beans, and their phosphorus uptake, were decreased, but these characters were increased with larger dressings. Heavy dressings, from 4 to 16 cwt triple superphosphate, increased yield of these crops. Similar effects were observed with maize during growth and maturity was advanced, but final yield of grain was not affected by applied phosphate. The suggestion is made that in a long growing period the maize was able to absorb adequate phosphorus, even though the phosphate intensity in the soil was low, to achieve its potential yield.