Combined effects of termite activity and agricultural practices on soil physicochemical properties and aggregation in Southern India

Abstract

The soils of different agrosystems are studied simultaneously with termite activity in the context of long-term restoration project. The aim is to highlight the positive impact of termites on soil physicochemical properties. Previous studies have mainly focused on permanent structures built by those insects such as mounds, punctually impacting the landscape. In order to study a more widespread impact of termites, the temporary structures built for food foraging are compared to the underlying soil. It is assumed that, after rainfall or watering, these structures will return to the soil surface. The three sites are a fallow land (permanent pasture), a tilled field and agroecological raised beds. Termites only show up where there is organic matter, irrespective of its type. In the three sites, clay content, available K, Mg and P, organic carbon, pH, cation exchange capacity (except in the fallow) and exchangeable bases are increased in the biogenic constructions. The increase is generally lower in the beds because the reference soil already has higher values. In the field and the fallow, the aggregation is improved in termite sheetings, as the macroaggregates in both sites and the protected microaggregates in the field increase whereas the free microaggregates decrease. In the beds, the reference soil already has a better physical stability, with more macroaggregates and protected microaggregates. Our results demonstrate that agricultural conservation practices are able to improve most of the soil properties in the same way that for ecosystem engineers such as termites.