Standard practice in conventional apple orchards is to control weeds with herbicide. This reduces soil microbial diversity, and in sandy soils creates a bare soil surface which crusts and is impenetrable to rainfall, leading to excessive runoff. Many orchards are mixed plantings that may include apples, pears, stone fruit, citrus or other fruits and possibly some seasonal vegetable crops. Production of apples needs to be considered as only one component of an integrated whole farm system. The inclusion of other fruit crops from unrelated botanical families, as well as soil regenerating pasture or green manure phases and the use of other plants species can have implications for management of pest, disease or weed control. The whole system should be designed and managed to optimise benefits and minimise problems across all crops arising from treatments to any one crop. The layout of cropped areas may change towards more mixed cropping as a way of breaking up large areas of a single crop, thereby increasing biodiversity and assisting pest or disease management. ChemFree systems are primarily biological systems, both above and below the soil. Pest, disease, and weed control need to encourage and maintain natural biological processes so as to balance disease and pest problems. Enhancement and manipulation of these biological processes form the basis of organic management.
Other control measures can include:
• choice of crop species and varieties;
• orchard layout and tree structure and canopy management;
• orchard hygiene;
• orchard floor species mix;
• mulching and mowing regimes;
• biological control and maintenance of beneficial predator habitats;
• mechanical controls such as traps, barriers, light, sound and pheromones.
When designing an orchard begin with a relative weed-free site. Starting with a site that is relatively free from serious problem weeds is an important pre-requisite before committing to a ChemFree production system. Vigilant monitoring and timely management of problem weed outbreaks will be important to ensure serious infestations do not get established.
Mowing and mulching
A well-established plant cover, of preferred species, over the orchard floor provides the basis for out-competing and controlling weeds. Managing the orchard floor cover requires periodic mowing and mulching, and these events can be designed and timed to optimise the impact on target weeds.
A common machine used is a tractor mounted mower with spring loaded retractable outrigger that moves around trees trunks. The height and timing of cutting can influence the growth and flowering of different orchard floor species and hence their ability to attract beneficial insects. Leaving occasional strips un-mowed at certain times can assist in maintaining biodiversity.
Different mowing options should be considered for early and late in the season. One grower reported using a modified hay cutter twice early in the year to keep cut grass long and lain flat. Finely chopped up grass tends to decompose quickly, so tall grass is cut with a hay cutting action in the spring which gives a slower breakdown and helps conserve water and builds biological activity and humus formation. Later in the year a mower with outrigger is used.
For new tree plantings, the use of heavy straw mulch down rows during the first few establishment years is common practice. The use of barley as an initial cover crop followed by sowing selected orchard floor species can give a solid cover that allows mowing and mulching down the young tree lines. A brush cutter can also be used around young trees and other areas where necessary.
The strategic use of chooks (in mobile housing), positioned to impact on problem weed hot spots, has been used with success. Sheep can also be used for weed control at strategic times of the year. It can be important to balance soil minerals to prevent sheep from eating the bark.
Fruit thinning
Fruit thinning needs to be done early before physiological impact, thus minimising biennial bearing problems. Hand thinning or a number of organic acceptable substances such as an application of lime sulphur in cool weather during or just after bloom can cause blossom and fruit thinning. One report suggests rates of around 1 litre per 95 litres can be applied at up to 10 per cent bloom without leaf burn. Other options reported to assist fruit thinning are the use of biodynamic 501 silica spray. Research in Switzerland has demonstrated that vinasse (a by-product of molasses) and mechanical thinning with a rope thinner have good potential.
