Agriculture Reference
In-Depth Information
their certifying agency's guidelines. For commercial products, purchase only
those that you know, by brand name, are approved for organic production.
If they are not specifically approved by OMRI or another recognized organic
certification organization, avoid them.
There are a few exceptions, including the phosphorus and potassium
amendments we discussed earlier. While rock dusts and humate products
have little to offer orchardists, zeolites can be beneficial in cropping systems.
According to the U.S. Geological Survey (USGS), “Zeolites are porous miner-
als with high cation-exchange capacity that can help control the release of
plant nutrients in agricultural systems. Zeolites can free soluble plant nutri-
ents already in soil, and may improve soil fertility and water retention. Be-
cause zeolites are common, these unique minerals could be useful on a large-
scale in agriculture.” Zeolites are most useful on soils with low CEC and act
rather like sponges, holding and releasing plant mineral nutrients. In chapter
8 , we will go into more detail on other plant nutrient sources and programs
to use after you have planted your crops.
Weed and Pest Control
At this point, we have corrected soil drainage problems, laid out planting
blocks and other operating areas of the orchard, adjusted the soil pH, and
amended the soil (according to soil tests!) to ensure adequate nutrition for
our orchard crops. The next step is to address pre-plant weed control. Elim-
inating the most serious weeds or bringing the populations under control is
a key step in establishing a healthy, productive orchard.
Until the late 1990s, we generally referred to managing vegetation on the
orchard floor as weed control or weed management. Prior to the 1950s, trees
were planted far apart in orchards to allow cross-cultivation and keep orch-
ard floors bare of vegetation. As a result, the soil of these orchards was of-
ten heavily eroded and compacted, and it was difficult to access trees in wet
weather. As preemergent and selective herbicides became available begin-
ning in the 1950s, many orchardists began maintaining grass in alleyways
and eliminating all grasses and broadleaf weeds in the tree rows. This re-
 
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