Two Experiments on the Effects of Heavy Applications of Triple Superphosphate On Maize and Cotton in Buganda Clay Loam Soil

Abstract

In Uganda although values for available soil phosphorus as measured by the Truog method are sometimes low and the growth of indicator plants in pot tests is very often limited by lack of phosphate, worthwhile responses to phosphate fertilizers have rarely been obtained in a total of about 80 field experiments at 30 departmental sites. Results obtained at the Grassland Research Station, Kitale in Kenya III and later work by Le Mare at the Cotton Research Station in Uganda [21 has suggested that heavy applications of superphosphate might significantly increase crop yields where moderate applications were ineffective. It therefore seemed advisable to see if such heavy applications would be effective at the Department of Agriculture's main research station at Kawanda, near Kampala, where the soil is typical of that covering much of south Uganda. Two experiments were accordingly started in 1960: one experiment tested a high rate of phosphate, applied in various ways thought likely to increase its effectiveness, in conjunction with other manurial treatments, the other and smaller experiment determined the responses to phosphate with and without lime.