Contribution to the study of olive mill by-products application to agricultural soils. Effect on various chemical parameters related to soil fertility, plant nutrition and the productivity of some crops

Doutoramento em Engenharia Agronómica - Instituto Superior de AgronomiaThe aims of this study were to contribute to a better knowledge of the effects of land application of olive mill wastewater (OMW) and two-phase olive mill waste (TPOMW) and, also, to obtain data necessary for the development of the best practices concerning the application of those by-products to agricultural soils. Several trials were set-up: (i) incubation trials on four different soils (VReu, CMhu, LVfr and CMca); (ii) seed germination tests and (iii) greenhouse pot trials on two soils (CMca and CMdy), using barley as test plant; (iv) a field trial was established on an olive grove located in a calcaric Cambisol, near Santarém, were the application of 80, 160 and 240 m3/ha·year of OMW was evaluated along three years. In conclusion, the controlled application of OMW and TPOMW to agricultural soils can be an adequate option for these wastes, as it causes neither acidification nor salinisation of the soil. In addition, the yield and the quality of the crop are also not affected. The Portuguese legislation concerning the agricultural use of OMW should be revised, as it imposes some unnecessary limitations, in the author’s opinion. On the other hand special attention should be given to the fact that these wastes lead to a decrease on the nitrate levels in soil