Effects of soil application of olive mill waste water, solid olive mill waste and a compost on total and mineral nitrogen and on organic carbon

Abstract

Olive mill wastes application to agricultural soils, directly or after composting, could represent a valuable option for their disposal and a good strategy for their valorization.

The aim of the experiment was to evaluate the effects of soil application of olive mill wastewater (OMW) and solid olive mill waste (SOMW) from a three phases olive mill, as well of a compost (C) obtained from a mixture of these byproducts with organic matter residues from gardens and croplands, on soil total and mineral nitrogen, on organic carbon and on carbon/nitrogen ratio.

Two factorial pot experiments were established using Hordeum vulgare var. Sereia as test crop and two soils – a Calcaric cambisol (CMca) and a Dystric cambisol (CMdy). The experiment was arranged into completely randomized blocks, with three replications, performing ten treatments. Four levels – 0, 80, 160 and 240 m³/ha – of each product were applied.

The obtained results showed a significative increase (p≤0,05) on organic carbon, total nitrogen and C/N ratio, in both soils by SOMW and C application. An initial significative decrease (p≤0,05) on NO3-N was verified with the application of OMW and SOMW on the CMca soil. Results showed that composting avoid initial nitrogen immobilization can be a better alternative to those by-products.