Evaluation des propriétés physicochimiques liées à la disponibilité du phosphore des différents types de sols du Burundi

Abstract

In order to evaluate the physicochemical properties related to the availability of phosphorus of the major soil groups of Burundi, twenty-two composite samples of soils taken were analyzed. Granulometry, organic carbon, pH, available phosphorus, total phosphorus, exchangeable cations and exchangeable aluminum are the parameters analyzed. The results obtained show that more than 68% of the soils studied have a pH lower than 5.5. For grain size, more than 59.1% of soil have a clay texture. The organic carbon contents obtained vary from 0.60 to 5.33 % and more than 40.9% of cases have levels reaching the critical threshold (1.2 to 2.5%). The cation exchange capacity varies from 4.62 to 50.93 meq/100g and more than 63% of cases have a low cation exchange capacity. The aluminum ion is present in more than 17% of the soils studied. The exchangeable calcium contents vary from 0.285 to 32.27 meq /100g and 22.73% of the soils have contents reaching the critical threshold (2.3 to 3.5 meq /100g). The levels of exchangeable magnesium  from 0.03 to 7.04 meq /100g with 18.18% of cases having levels reaching the critical threshold (1 to 1.5 meq/100g). The exchangeable potassium contents are between 0.13 and 0.64 meq /100g with 45.45% of cases being
within normal values (0.2 to 0.4 meq /100g). The available phosphorus contents vary from 0.98 to 39.57 ppm with more than 90.9% of the cases being low in available phosphorus. The low levels of available phosphorus observed would be related to the texture, the pH, the low levels of
 bases, the exchangeable acidity and the low levels of organic matter. Depending on the problem  , the addition of calcium or magnesium amendment, organic matter and phosphate fertilizers could help improve the physicochemical properties and mobilize phosphorus in these soils.