Changes in p pools over three months in two soils amended with legume residues

To assess the longer term effects of soil properties and residue addition on soil P pool concentrations, we added residues from three different legumes to two soils and measured the concentration of soil P pools over three months. The size of various P pools was assessed by sequential P fractionation on days 0, 14, 28, 56, 70 and 98. Compared to the unamended control, addition of faba bean and chickpea residues increased the concentrations of resin P, microbial P, NaHCO₃-Pi temporarily whereas amendment with white lupin residues had little effect on P pool concentrations. The decrease in NaHCO₃-Po and NaOH-Po towards the end of the experiment coincided with an increase in NaOH-Pi in Mt. Bold soil and of HCl-Pi in Monarto soil. These temporal changes were more pronounced in soils amended with faba bean and chickpea residues than in the unamended soil or after addition of white lupin residues. The principal component analysis (PCA) plot showed that the P pool concentrations on days 0 and 98 were quite similar and differed from those on days 28, 56 and 70 suggesting clear temporal patterns. The results of this study show that the concentration of various P pools is strongly affected by soil properties such as pH and organic matter content and further modulated by the properties of the residues.M. Alamgir, P. Marschne