Pepper cultivation on a substrate consisting of soil, natural zeolite, and olive mill waste sludge: changes in soil properties

Abstract

The distribution of olive mill waste (OMW) in soil under specific conditions and restrictions seems to be an advantageous choice considering that it is a low-cost method and it recycles nutrients and returns organic carbon to the soil. In addition, it is regarded as a practice that contributes to climate change mitigation. The aim of this research was to investigate the potential of the natural zeolite clinoptilolite as a soil additive for using OMW sludge for vegetable cultivation and for eliminating the risk of soil and underground water degradation. For this purpose, a pot experiment was conducted under greenhouse conditions in which pepper seedlings were transplanted and grown onto different substrates containing combinations of 0%, 2.5%, and 5.0% zeolite and 0%, 2.5%, and 5.0% OMW sludge (v/v). The plants were irrigated twice a week, while leachates were collected on a weekly basis for testing. The results indicate that the use of OMW sludge improved soil properties. Moreover, the use of clinoptilolite as a substrate did not cause any significant variations in the cultivation process although this led to an increase in exchangeable Na at phytotoxic levels. However, it was determined that the substrate consisting of 2.5% clinoptilolite and 2.5% OMW sludge produced the best results in terms of substrate and leachate properties. The results are considered to be useful in effectively treating OMW when combined with natural zeolite additives as this process enhances the physicochemical characteristics of soil without leading to major irreversible negative consequences.