The influence of soil phosphorus, pH and texture on the uptake of phosphorus from soil and fertilizer by upland rice
AbstractAt six sites in 1987, and two sites in 1988 in the Tai region of south-west Cote d'Ivoire, long-term field trials were started to study the supply of nutrients from the soil and the response of food crops to fertilizers. The results for P during the first season after removal of the primary or secondary forest vegetation in experiments with rice are described. P rates were 0 or 50 kg/ha in 1987, and 0, 12.5, 25 or 50 kg in 1988. The application of 50 kg P increased grain yield by 0.5-1.0 t/ha at five of the six sites in 1987. In 1988, a similar response could be obtained with lower rates of 12.5 or 25 kg P ha. At all sites, P application increased P uptake significantly, but the recovery of fertilizer P decreased with increasing P application rates. The soil P supply was best described by an equation including P-Dabin (a modified P-Olsen method), total P and pH. The recovery of fertilizer P could best be described by equations including silt plus clay content, P-Dabin, and/or total P. Since some soils had a high gravel content, soil analytical data, referring to the fine earth (<2 mm) fraction of the soils and expressed on a mass basis, were translated to values expressed on the basis of volume of total soil. This conversion substantially improved the relations between soil properties and P uptake or fertilizer-P recovery.
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