Agroforestry of olive groves in the Sfax region with cover crops or grazed crops
Olive growing in arid climates is based mainly on monoculture with intensive tillage since decades. This practice, with lack of organic fertilization and pruning material turnover, induces soil degradation, soil fertility loose and enhanced erosion. Thus, olive productivity and resilience to climate change dropped with less income to farmers. Sustainability of olive producing system is under serious threats especially due to resources depletion and climate change.
Intercropping legumes and cereals in olive groves could be a sustainable practice that can improve soil fertility, crop yield and enhance diversification. The diversity of plant species improves productivity as well as increasing organic carbon (C) and total nitrogen (N) stocks in soil, microbial biomass, and crop residues. Agroforestry system based on olive, tends maximize synergies between trees and associated crops, especially in areas sub-jected to water scarcity and harsh climatic conditions.
Codesign workshops
Field experiments
Main results
The intercropping of olive with barley resulted in an increase of water storage in the soil even though the very low rainfall during the growing season. This permits a minimal water availability during summer period. Faba bean permitted and in-crease of soil organic matter content. Cereals were effective in improving soil assimilable potassium and reducing pH and assimilable sodium. The association of faba beans in the olive grove reduced soil pH and assimilable sodium and improved assimilable potassium contents. Over the two trial periods, the use of intercrops in the olive grove was effective in improving soil fertility. Agroforestry improved bacterial communities while fungi population was improved by barley intercropping.
Intercropping of olive tree with faba bean induced a better vegetative growth of olive tree and the most important produc-tion of the whole biomass. During the first year the native vegetation was the most efficient when compared to faba bean and barley. In the second-year barley and faba bean has better results. Olive with cover crops system needs an adaptation period due to the competition with native vegetation.
On-farm field experiment of intercropping Barley and Faba been in rain-fed olive orchard resulted on:
✓ Improved soil water content,
✓ Reduced the salinity and increased soil organic matter and calcium contents.
✓ Keeping native vegetation increased only soil organic matter content.
✓ Enhancing soil nitrogen and potassium contents via Faba bean effectiveness.