Agriculture Reference
In-Depth Information
seeds and become weeds themselves. Avoid using sod-forming crops, such
as turf grasses.
Solarization
University of California orchard specialists recommend solarization as one
means of reducing weed populations in the crop rows before planting trees.
To solarize the soil, stretch one, or preferably two, layers of clear, 2 to 4 mil
plastic film over bare, moist soil and cover the edges of the plastic with soil.
Make sure that the soil is smooth, level, and free from clods and surface
debris. The plastic should be as close to the soil as possible. Under ideal con-
ditions, the top 2 inches of soil will be heated to around 140°F (60°C) and
soil 18 inches deep will be as hot as 102°F (39°C). These temperatures are
high enough to kill many seeds and pathogens. Nematodes in the top several
inches of soil may also be killed. The films may need to be left in place an
entire summer.
Solarization works well in parts of California and other areas with hot
summers and clear weather, but in cooler or cloudier areas, it has proven to
be ineffective. In cooler climates, the plastic films serve as greenhouses, pro-
ducing lush weed growth under the plastic. Solarization also creates a dis-
posal problem for the plastic film, which is usually derived from a nonrenew-
able resource. Except for very small-scale growers in hot climates, solariza-
tion is not recommended.
Nonorganic Herbicides
At the risk of offending some readers, there is another strategy for bringing
serious weed problems under control before establishing orchard trees. For
sites heavily infested with hard-to-control perennial weeds, some orchardists
elect to use synthetic, translocatable herbicides to kill the weeds during their
transition to an organic orchard. While I do not promote this practice for or-
ganic fruit growers, it is an option for reclaiming a badly maintained site and
converting it to a productive organic orchard.
