Responses of sweet sorghum to sources and rates of phosphorus under greenhouse conditions: I. Dark red latosol

Abstract

A comparision was made of the efficiency of a rock phosphate from Catalão, Goiás, Brazil (FG) with that of concentrated superphosphate (ST) in a Dark Red Latosol (LEa) from the same region. Four rates of were used in presence and absence of liming. Residual effect was followed in two successive crops. Main conelusions were the following; ST was a better source of P2O5 than FG; liming increased the effect of FG to the extent of circa 50 per cent of the efficiency of ST when the three crops were considered together; the method of application, placement against mixing, did not influence dry matter yield; P uptake was positively influenced by liming, especially in the second and third crops; there was a significant, positive correiation between residual P in the soil, evaluated by bicarbonate extraction, and dry matter; better correlations, however, were found between soil exchangeable Ca and yield.