Solutions to restore degraded Soils in mediterranean OLive orchards Via Organic mulch and biochar from olive industry waste.

The recent introduction of superintensive irrigated olive groves in the Mediterranean, with up to 2000 olive trees per ha, poses new concerns about poses new concerns about soil and water resources. Unsustainable management practices will trigger desertification, and lead to land degradation by soil erosion and soil fertility losses, compromise long-term food security as well as water availability through the silting of water bodies. Desertification is anticipated to intensify, with climate models predicting warmer and drier scenarios, with more frequent extreme rainfall events. At the same time, the oleic sector faces a great challenge in dealing with olive mill waste, requiring the development of new technologies to neutralize and/or valorize these phytotoxic residues.

SOLVO aims to simultaneously address both these problems by engineering innovative nature-based solutions that combine mulch, derived from olive residues, with biochar, derived from olive mill wastes (OMW), to reverse soil degradation in low fertility olive orchards (very low SOM and highly vulnerable to soil threats). SOLVO will take advantage of the availability of olive residues, the easy and economic surface application of mulches, and the instant increase of soil carbon through a single application of biochar, as a low-turnover, recalcitrant carbon source. There is already proof that this method is effective at reducing soil erosion and increasing SOM, and it is now important to assess the effects on other soil-mediated ecosystem services (ESs) at wider spatio-temporal scales. SOLVO aims to assess the potential contribution of mulch-based solutions to the delivery of soil-mediated ecosystem services (ESs), specifically: 1) erosion control; 2) water storage; 3) carbon storage; 4) soil fertility and 5) soil habitat. The specific objectives are:

1. to select mulch and biochars from different olive oil agro-wastes, at application rates and schemes that maximize the soil restoration capacity of the treatment;

2. to assess the effect of selected mulches on soil-mediated ESs in degraded olive orchards across spatial scales;

3. to assess the treatments’ life-cycle performance and the environmental suitability and predict the performance within broad temporal and spatial scenarios, useful as decision-support tools for land managers.

The SOLVO´s results will contribute to: i) improving food security and promote sustainable agriculture (SDG2); ii) restoration and conservation of soils and enhancing of ESs, thus combatting desertification (SDG15); iii) increasing soil carbon stocks, which will enhance the resilience and adaptive capacity to climaterelated hazards and natural disasters (SDG13); iv) improving water quality by reducing erosion and pollution of waterbodies (SDG6); v) increasing the opportunities for value addition of residues by using residues as a tool to reverse desertification (SDG2).