Glomalin related soil protein, carbon, nitrogen and soil aggregate stability as affected by land use variation in the humid forest zone of south Cameroon

Arbuscular mycorhizal fungi (AMF) produce a glycoprotein (glomalin) which play an important role in the maintenance of soil structure and fertility. On the other hand, it can be used to evaluate the impact of agricultural practices on soil quality across many land use systems. We assessed land use impact on glomalin related soil proteins (GRSPs), soil quality and aggregation in the humid forest zone in southern Cameroon. Forest, short fallow and field crop production soil samples were used to determine GRSPs, carbon (C), nitrogen (N) and water stable aggregate (WSA1–2mm). Results showed that GRSPs significantly decreased from the forest to fallow and the field crop production systems. The easily extractable GRSP (EEGRSP) was 30% and 39% less under fallow and field crop production respectively, relative to the forest soils. Similarly, total GRSP (TGRSP) was 17% and 46% less under fallow and field crop production respectively, relative to the forest soils. C, N, and organic matter (OM) did not change significantly within the land use systems. The WSA1–2mm was 20% less under fallow, and 33% less under field crop production relative to the forest system. However, AMF spores augmented from forest to fallow and field crop production system. There was a positive correlation between GRSPs (EEGRSP, TGRSP) and AM fungal spore density suggesting the possible implication of these fungi to the production of the GRSP in this zone. There was also a positive correlation between C, N and EEGRSP, suggesting the implication of GRSP in stocking soil C and N in this zone. Likewise, a positive correlation between OM and TGRSP was found meaning the implication of GRSPs to OM pools in the soil of this zone. WSA1–2mm was also correlated with TGRSP, C and OM, suggesting the possible coactions of GRSP, OM to the formation of WSA1–2mm, and thereby promoting the build up of soil structure. These results highlight the view that GRSP can be used as an indicator of soil quality in this region and should be considered as a criteria when define agricultural management strategies. AM fungal and GRSP might be useful to monitor soil degradation in this zone.

► Impact of land use systems on soil properties in the humid forest was tested. ► The variation of AMF density, GRSP, soil aggregate and soil OM was noted. ► High relationships exist between soil aggregate stability, GRSP and soil OM. ► GRSP could be used as indicator of soil quality.