Organic weed management in perennial fruits

- Weed management in organic orchard is contingent on the type of weeds present and soil fertility status.
- Mulches (manufactured and organic) restrict nutrient management options on infertile sites.
- Dead organic mulches alone are not adequate on sites with perennial rhizomatous weeds.
- Living mulches are only appropriate on fertile sites with adequate moisture and intense mowing.
- Tillage is the most appropriate option on sites with low fertility where amendments need to be applied.

Weed management is key component of establishing and sustaining a profitable organic orchard. Good site preparation is a critical part of an orchard establishment plan. Pre-plant weed control coupled with addressing soil fertility issues before planting can dramatically increase the options available to producer for weed management, while reducing the time to commercially viable levels of fruiting and harvest. Tillage may be the best option on sites with perennial rhizomatous weeds and low soil fertility, or where there is high risk of rodent damage to the crop. Dead organic mulches are best suited to sites with low presence of perennial rhizomatous weeds and sites where at least moderate levels of soil fertility are present. While living mulches tend to provide a desirable habitat in the orchard understory, they are competitive with the crop for water and nutrients, regardless of whether they are mowed or not. They should only be used on sites with good background soil fertility, with frequent mowing, and where climate or irrigation minimize risk of moisture stress. Most manufactured mulches can provide effective weed control for a longer period of time but reduce soil fertility management options. The use of biodegradable mulches under dead organic mulches poses interesting possibilities and should be studied further. Organic herbicides are presently not effective enough or too costly to be used as the primary means of weed control but would be a useful tool for spot and edge control of weeds in mulches.