Preliminary trial of ex situ inoculation of earthworms, hyperiodrilus africanus for the restoration of degraded soils in the Kikwit region of the democratic Republic of Congo

Soil macroinvertebrates, including earthworms, provide ecosystem services that are now considered key to the implementation of ecologically intensive agriculture. In order to improve the productivity of very poorly fertile and particularly acidic soils, the present study aims to inoculate earthworms for maize production under the edaphoclimatic conditions of the Kikwit region of the DRC. For this purpose, a trial was carried out in a completely randomized system, to better test the feasibility of introducing these engineers into the soil to improve the productivity of agrosystems. In soilless mesocosms, the inoculation of earthworms positively influenced the growth in height and diameter of maize plants on the 45th day of cultivation by 109, 37±3.7cm and 1.866±0.25cm respectively compared to the control with 82.07±4.92cm and 1.233±0.06cm respectively. The results still show that earthworms had a significant effect on all production and yield parameters. At harvest, the yield was 3±3tons.ha-1 of dry corn kernels, an increase of 46% over the control. The texture was on average 87.9% sand, 7% clay and 3.3% silt, so it was sandy-clay. In the presence of earthworms, we observed a relatively fine granulometry, from 50 to 250 µm. Regarding agronomic properties, the corn plants had a much better growth in height and diameter and the yield in dry corn grains is very high, up to 3 ton.ha-1 and thus exceeds 46.3% in the presence of earthworms. Physical properties such as soil aggregation, porosity and water use efficiency improved in the earthworm treatments. Soil ingested by earthworms has a slightly finer particle size and is rich in clay. Chemical properties, such as C and N stock, mineralization of nutrients such as assimilable P, Mg++, Ca++, K+; pH and CEC, were very positively influenced by earthworms. All these chemical properties, their content is significantly higher in earthworm castings than in the surrounding soil. Biological properties, such as the stimulation of nitrifying bacteria for the degradation of organic matter, source of the maintenance of the high content of C and N, were very significantly influenced by the presence of earthworms. The inoculation of earthworms, therefore, in sandy soils that are particularly acidic and poor in biogenic elements, constitutes a serious alternative to the use of inorganic inputs that are not within the reach of small farmers. It allows to improve production, yield, carbon sequestration and erosion control in agrosystems.