Long-term kinetics of phosphate desorption from soil and its relationship with plant growth

Abstract

Knowledge on the availability of residual P in soils is of great importance for fertilization management. The use of dialysis membrane tubes filled with hydrous ferric oxide solution has recently been reported as an effective way to characterize P desorption over long-term laboratory studies. However, there is relatively little information relating the desorption indices of this method to plant parameters. The objective of this research was to relate the kinetic data generated using the DMT-HFO method to shoot dry matter yield of maize grown under greenhouse conditions. Accordingly, the labile pool rate coefficient (kA) showed a highly significant correlation with both shoot dry matter yield (r = -0.994**) and plant P uptake (r = -0.982**). The less labile rate coefficient (kB) also showed a significant correlation with both shoot dry matter yield (r = -0.856**) and P uptake (r = -0.893*). The correlation between the cumulative P extracted and shoot dry matter yield was highly significant. A strongly significant correlation was also observed between Bray 1P and shoot dry matter yield. Judging from the r-values, both the kinetic parameters and the cumulative amount of P desorbed could serve as reliable indices of plant available P revealing the effectiveness of this method in estimating the availability of residual P in soils. However, assessment of the reliability of this method at field level is important. Data from a wider range of soils is necessary to evaluate the universality of this method.