Long-term effects of olive mill waste waters spreading on the soil rhizospheric properties of olive trees grown under Mediterranean arid climate

Abstract

Context

The spreading of olive mill waste waters (OMWW) could offer an appropriate management option to add value to this agricultural by-product, such as to increase soil fertility and plant productivity.

Aims

The main objective of this work was to evaluate the effects of the application of OMWW (at a fixed dose of 50 m³ ha⁻¹), in the long term (20 years) on the soil rhizospheric properties and on old olive trees (80 years old) growth and productivity.

Methods

The experimental site consists of four plots treated with OMWW (T₁, T₂, T₃ and T₄) and four ‘control’ plots (C₁, C₂, C₃ and C₄), without any treatment. The treated plots have received each a fixed dose of 50 m³ ha⁻¹ of OMWW in February of each year since 2004.

Key results

The results obtained showed that the addition of OMWW increased the soil water retention capacity (SWRC) and its organic matter content (OMC), as well as the augment of phosphorus (P) and potassium (K) levels. The activity of the soil rhizospheric microflora was significantly enhanced.

Conclusions

OMWW application to the soil surface in an olive orchard at 50 m³ ha⁻¹, since 2004, had no negative effects on the tree’s vegetative growth and satisfied plant P, K and N requirement.

Implications

Our study showed that OMWW can enhance the soil properties and enrich the soil with necessary minerals.