Description of the Business As Usual (BAU)
The general soil management in olive orchard is conventional tillage or bare soil with herbicides, sometimes mixed with minimum tillage. Pruning residues usually are removed or burned in the field.
Description of the system change
Pruning residues used as mulch (the term ‘inert cover’ in woody crop is also found in the literature) consists of maintaining shredded pruning residues on soil in the area between tree rows. This system maintains a permanent ‘inert’ cover protecting the soil against erosion events. Furthermore, pruning residues provide a significant amount of carbon input to the soil improving the soil organic carbon. Pruning residues should be shredded to form a mulch spreading residues on the soil, and it is needed to allow the pass of machinery. In addition, shredding is needed to control pests like, Phloeotribus scarabaeoides. With this technique, at least 30% of the soil should be protected, otherwise, it should be complemented with alive groundcovers. It depends on the age of plantation, trees size and the frequency of pruning operation, having the olive trees usually a biennial basis.
Before the shredding machine pass, pruning residues should be placed in the inter-row manually or through a windrower machine. Shredded pruning residues have an allelopathic effect controlling spontaneous flora. Outside the strip of pruning residues mulch, weeds must be controlled by mechanical mowing, chemical spraying or grazing when olive trees are in a phenologically sensitive stage such as flowering. Likewise, weeds that could appear inside the mulch strip should be controlled. Along the season, more than one control may be necessary. The control timing would change according to meteorological conditions, but it must be taken care of the main crop to prevent competition for water and nutrients. Shredding machine pass also performs mowing effect controlling weeds.
Pruning residues mulch (as well as seeded groundcovers) is a good alternative when there is low seed bank in the soil for spontaneous groundcovers, what happens especially when the BAU used pre-emergence herbicide or frequent tillage passes.
The weeds control in the tree row should be conducted as BAU. Herbicide control is the common system through spryer with the central nozzles locked to keep the groundcover in the inter-row. Other other strategies are also usual like mowing with adapter mower, hand brush cutter or grazing. In super-intensive orchards
(1200–2500 trees/ha) inter-vine mower/blade is also used to remove weeds by mowing or tilling the crop row.