Agriculture Reference
In-Depth Information
of composts or mulches. Because laboratory tests measure the decomposed
portion of organic matter, and not pieces of roots or other visible plant ma-
terials, organic matter concentrations in the soil change slowly. Given effect-
ive orchard floor management practices, losses of organic matter should stop
within a year or so of transitioning to organic or starting a new orchard, and
levels should gradually increase over 10 to 15 years. On sandy soils in arid
climates, 3 percent SOM is a good target, while 5 percent is reasonable on
loamy soils. The goal is not to increase soil organic matter concentrations for
the sake of increasing them but rather to develop and maintain a biologically
diverse and active soil with good structure and adequate, but not excessive,
plant nutrient concentrations. Monitoring soil organic matter, as well as tree
health and productivity, will help you track your progress. Because testing
procedures (and therefore the results) for soil organic matter differ between
laboratories, find a good lab and stick with it. If you switch from one labor-
atory to another between years, you will not be able to accurately compare
results for different years or track your progress.
How we manage an orchard floor has great impact on organic matter.
Cultivation and bare-ground treatments cause soil organic matter concen-
trations to decrease. Green manure crops, alley and in-row companion crops,
and mulching increase soil organic matter.
Controlling Weeds
Some organic practitioners object to the use of the word “weed,” believing
that all vegetation in an orchard is desirable. For our purposes, we will con-
sider any plant growing where we do not want it to be a weed. Regardless of
semantics, vegetation management on the orchard floor is critically import-
ant while we are establishing our trees and remains important throughout
the life of many orchards.
It is important to understand that any time we create a vegetation-
free area, we have created a vacuum that nature will strive to fill. As with
any ecosystem, highly aggressive, invasive, and competitive plant species
have the advantage over our nonaggressive and relatively slow-growing fruit
