Growth, yield and nutrient status of pepper plants grown on a soil substrate with olive mill waste sludge and natural zeolite addition

Due to the importance of further disposal of olive mill waste sludge (OMW) on cultivated soils as an alternative way of their handling, as well as to the properties of natural zeolite clinoptilolite, the aim of the present work was to investigate the effect of OMW and zeolite addition on a soil substrate, on the growth, yield and mineral nutrition of 'flask' pepper plants. Nine treatments were applied in total, derived from the combination of three levels of OMW (0%, 2.5% and 5%) and three levels of zeolite (0%, 2.5% and 5%). Regarding plant growth and yield results, the leaf biomass of plants grown with 2.5% OMW remained statistically unaffected compared to plants grown without OMW addition. Moreover, plants under 5% zeolite and 2.5% OMW presented higher fruit biomass compared to plants under 2.5% zeolite and 2.5% OMW, whereas plants under 5% OMW with whatever zeolite level, produced the lowest yields. The nutrient element results showed that leaf P, Mg Fe, Zn, B and nitrates concentrations increased contrary to the decreased leaf Na whereas leaf N, K, Ca, Mn and Cu remained invariable because of OMW addition. Zeolite addition increased leaf P, K and Ca but did not affect N and Mg concentrations. The above findings are of particular interest from the point of view of the utilization of OMW, contributing at the same time to a more rational crop fertilization recommendation.