Phosphorus isotopic evaluation of a Red Ferralitic soil under various fertilization systems

Soil samples from a red ferralitic soil from the 'Juan Tomas Roig' Experimental Station, belonging to Ciego de Avila University were analyzed under two crop rotations and four phosphoric fertilization systems. The objective was to evaluate, through the ³²P isotopic dilution, phosphor (P) static parameters in a soil that has received P fertilizer through two placement methods (banding and broadcasting) for several years. A radiochemical laboratory method using a free-carrier solution as a tracer based on isotopic exchange between solid phase and soil solution phosphate ions was used. Soil samples were analyzed at the CEA Department laboratories, in Francia. Quantity (), as isotopic exchangeable P at one minute, intensity (Cp), as P concentration in soil solution, and capacity, as (/Cp), factors were determined. ³²P isotopic evaluation indicated that the soil needs high banding P application to reach adequate and Cp values for crop nutrition. A cumulative P effect in the soil through banding fertilization after three crop rotation cycles was obtained, which allows to increase plant P availability. The capacity factor was very high in all soil samples, indicating that soil maintains a P reserve that is difficult to exchange with the phosphor present in the soil solution. (author)