The distribution of soil fertility index and its interaction with earthworms density under organic, semi-organic, and inorganic rice fields

Abstract

Earthworms are soil macrofauna that play a role in maintaining the sustainability of soil use through increasing organic matter and soil fertility. Soil fertility assessment is important to suggest management to create an optimum conditions for plant growth, so it can be maintained the quality and quantity of rice productivity. The purpose of this research was to identify soil fertility index (SFI), the density of earthworms and the relationship between the two under different rice fi eld systems, namely organic, semi-organic, and inorganic. This research also identifi es indicators that determine SFI to be able to provide appropriate and effi cient strategies in subsequent land management. This method used an exploratory descriptive with a survey approach. Sampling points was taken based on the farming systems (organic, semi-organic, and inorganic rice fi elds) on fl at (0-8%) and sloping (8-15%) slopes. The SFI was determined used the Minimum Soil Fertility Indicator (MSFI). The results showed that differences of rice fi eld farming systems is signifi cantly effects on SFI. The index of soil fertility in the research area is moderate, with the highest SFI in the organic farming system. Soil fertility and earthworms density had a signifi cant positive correlation, that the higher earthworms density, the higher soil fertility. Key indicators were found including organic C, available P, Al saturation, and exchangeable bases which determine SFI. The organic rice fi eld system has the best SFI as well as the highest earthworm population, so we recommend increasing the use of organic materials in the tillages process and expanding the organic rice fi eld system to maintain fertility and the sustainability of soil used for rice production.