The potentials of Albizzia zygia (DC) Macbride for soil amelioration

The capability of Albizzia zygia DC Macbride for amelioration of degraded cocoa soils was investigated by analyzing soil samples taken beneath its crown. Nodulation and nitrogen fixation activity in A. zygia were examined both in the field and greenhouse. The effects of soil moisture stress and soil acidity on nodulation and nitrogen fixation were also investigated. Higher levels of organic carbon, nitrogen, phosphorus, potassium and calcium were found adjacent to the trunk than outside the influence of the tree crown. The species is confirmed as nodulating and capable of symbiotic fixation. It also successfully nodulated when inoculated with a liquid culture of cowpea Bradyrhizobium. Although water stress and low pH significantly reduced nodulation and nitrogenase activity in A. zygia, the species showed an ability to nodulate and fix nitrogen satisfactorily under both drought and acidic soil conditions.