Utilization of olive mill waste liquids as soil amendment in northwestern coast (matrouh area) – Egypt

The reuse of industrial wastes and its by-products such as, olive mill waste (OMW) is beneficial to prevent or at least to reduce the environmental problems, where uncontrolled disposal of OMW is becoming a serious environmental problem. OMW is the main product generated by the olive oil extraction process, especially in the areas where olive cultivation is frequent, such as North Western Coast Zone of Egypt (NWCZ). Therefore, a field study was carried out during two winter seasons of 2015/2016 and 2016/2017 at Matrouh area, NWCZ of Egypt. Two field experiments were conducted for olive trees and corn plants, where each experiment included five treatments with four replication. The treatments were control (without any soil conditioner application, C), olive mill wastewater (OMW) at the rate of 20m³.fed^-1, (O), compost farmyard manure FYM with OMW at the rate of 10t.fed^-1, (FO), compost FYM at the rate of 10t.fed^-1(F) and compost FYM with effective microorganisms (EM) at the rate of 10t.fed^-1(FEM). Data illustrate that the soil of the experimental site is approximately shallow, light soil textural class, calcareous, non-saline, and poor in organic matter and CEC and consequently low in fertility. The differences in pH values for the different cultivation types that used the same amendments are very low and it can be avoid them. The percentage decrement is reach to 41, 60, 52 and 67% under olive cultivation and 40, 47, 44 and 53% under corn cultivation, for O, FO, F and FEM treatment, respectively. The average percentage increment of available water is 8, 39, 23 and 50% for O, FO, F and FEM treatments, respectively. Using FO or FEM caused decrease bulk density compared to using O only by about of 11 and 16%, respectively. Regardless the crop type, the efficiency of the used OMW and compost in increasing organic matter content can be arranged in the following order: FEM > FO > F > O, respectively. The levels of total nitrogen, exchangeable potassium and available phosphorus for the soils that treated by OMW amendments is higher than that for the initial soil. Regardless crop type, the average increment percentage for Fe, Mn, Zn and Cu varied from 148 to 250%, from 43 to 90%, from 97 to 142% and from 38 to 118%, for F and FEM treatments, respectively. The percentage increment of olive fruits yield reached 57, 38, 32 and 19% for FYM, FO, F and O treatments, respectively, while, the respective values for corn grains reached 58, 45, 41 and 8%, respectively, as compared to that for traditional cultivation.