GLOMALIN, CARBON, NITROGEN AND SOIL AGGREGATE STABILITY AS AFFECTED BY LAND USE CHANGES IN THE HUMID FOREST ZONE IN SOUTH CAMEROON

Arbuscular mycorhizal fungi (AMF) produce a glycoprotein (glomalin) important for soil structure, fertility and therefore plant nutrition which can be used to evaluate the impact of agricultural practices on soil quality across many land use systems. In the present study, its influence was investigated on soil fertility and aggregation in 3 different land use systems of the humid forest zone of southern Cameroon. Soils were sampled at 10 cm depth from 03 native forest, 03 fallow and 03 continuous growing fields systems at Metet (South Cameroon) for the determination of easily extractable glomalin (EEG), total glomalin (TG), carbon (C), nitrogen (N) and soil water stable aggregate of 1-2 mm diameter (WSA(1-2mm)). Results showed that both EEG and TG concentrations significantly decreased (P < 0.01) from the forest to the growing field, via the fallow system. The rate of EEG decrease was 29.82 % and 38.35 % in the fallow and the growing field system compared to the forest system, respectively. For TG, the decrease rate was 16.65 % to 46.04 % for the fallow and the growing field system compare to the forest system respectively; while C, N, and organic matter (OM) did not changed significantly. The proportion of C, N and OM were 93.6 %, 88.3 %, 93.7 % for the growing field system compared to the forest system respectively. The WSA(1-2mm) decreased from the forest to fallow and growing field systems, with respective rates of 19.69% and 32.81 %. There was high positive correlation between C, N and EEG (r(2) = 0.76, 0.55; P < 0.01), suggesting the possible implication of glomalin to soil stock of C and N. Likewise, the high positive correlation between TG and WSA(1-2mm) (r(2) = 0.64, P < 0.01), C and TG (r(2) = 0.84, P < 0.05), OM and WSA(1-2mm) (r(2) = 0.57, P < 0.01) as well as OM and TG (r(2) = 0.88, P < 0.01) suggests that glomalin, C and N may contribute to the formation of WSA(1-2mm), and thereby promote the build up of soil structure. These results highlight the view that glomalin can be used as an indicator of soil fertility in this region and should be consider as a criteria when define agricultural management strategies.