Phosphorus fixing capacity of a volcanic soil on the slope of mount Cameroon

摘要

The volcanic soils on the slope of mount Cameroon are deficient in available phosphorus (P) resulting in low productivity. Excess P could be a threat to the aquatic environment. There is therefore need to monitor the P-fixing capacity of these soils with depth. The transformation of applied P in soils from different horizons were examined after treatments with different P rates (0, 20, 60 and 180 mg P L-1) and incubation periods (one, three, seven, 14 and 28 days) under laboratory conditions. Phosphorus was extracted on each treatment combination to determine the amount of P fixed. Phosphorus recovered increased with added P. Phosphorus fixed increased with added P and depth throughout the incubation period. The soil showed a high P fixing capacity throughout the different horizons with P fixed varying between 57-99% in the upper horizons and 90-100% in the lower horizons. More than 90% of added P was fixed after one day of incubation. This therefore reduces the threat of eutrophication. Phosphorus fixed correlated positively with clay and pH, and negatively with organic carbon and available P. Clay had a significant (p<0.05) positive correlation with pH values. Clay and pH could therefore be responsible for P-fixation in this soil.