Agriculture Reference
In-Depth Information
of fruit tree diseases. Always select an orchard site that provides the best
possible airflow and water drainage away from the site.
Be careful, however, when planting on steep slopes. While you can find
orchards on very steep slopes, orchard operations become more difficult and
dangerous and the risk of soil erosion increases. If you must plant on a steep
slope, consider building terraces to create level planting areas. Figure 2.5
illustrates good and poor orchard sites.
Site History and Neighborhood
Before establishing an organic orchard, find out as much as you can about
the previous use of the site. This step is especially important if you plan to
become a certified organic grower because some previous activities can in-
terfere with certification. Arsenic, lead, and mercury, for example, are highly
toxic elements that were once widely used in agricultural pesticides, and
so might have been used on old orchard sites. Unfortunately, they are also
highly stable in the soil and persist for decades. If in doubt, have the soil
tested before you plant.
Another reason to be wary of old orchard sites is the risk of replant dis-
ease. This problem is particularly serious when following apples with apples.
Commercially, apple orchards have traditionally been fumigated prior to
replanting to help kill several fungal pathogens that inhabit the soil and
severely stunt new trees.
Replant disease is generally thought to be caused by a complex of several
pathogens that probably vary from one region to another. Throughout the
life of an orchard, these pathogens build up in the soil, although the estab-
lished trees often remain healthy. When the old trees are removed and new
trees planted, the new trees can die or remain stunted and unproductive.
While conventional growers fumigate the soil with highly toxic chemicals
(methyl bromide was once very popular for this purpose), soil fumigation is
not available for organic growers. If you are considering a site on which old
fruit trees were grown within the past few years, replant could become a ser-
ious issue, especially if you follow apples with apples. Some certified organ-
 
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