Application of olive pomace biochar as soil amendment for intensive olive crops

Abstract

The olive oil agro-industry is an important economic sector in Mediterranean countries, whose production is accompanied by the generation of huge quantities of organic waste. The recent proliferation of super-intensive olive groves, more profitable, generates a greater demand of water for irrigation and is increasing the production of organic waste. The conversion of these olive mill wastes into biochar by pyrolysis, for subsequent use as an organic amendment in super-intensive olive grove soils, could contribute to solving both problems, since biochar has a high porosity and a highly stable organic carbon content. Nevertheless, the effects of its application on soils properties and plant physiology are still not well known. This study addresses the effects of the application of olive mill pomace (alperujo) biochar, 100% vegetable compost (traditionally used organic amendment) and the mix of both organic amendments on the properties of a Xerochrept soil and on the physiology of “arbequina” olive trees”. The super-intensive olive trees plantation, with irrigation deficit, is located in the IRNAS-CSIC field station "La Hampa" (Coria del Río, Seville, Spain). Both biochar and compost reduced soil penetration resistance and increased soil organic Carbon and moisture content. However, the application of biochar was more effective than the addition of green compost or the compost+biochar mixture in increasing soil moisture. Biochar application improved soil physical properties and plant water status at the pre-harvest phase without increasing soil respiration (CO₂ emission) rates.