Horticulture Principles and Practices

preemergent or early postemergent operation. Tillage tools are variable and
used to accomplish various purposes. The shallower the depth to which the soil is
disturbed, the fewer the weed seeds that will be brought to the soil surface to
grow. Row crop and interrow cultivation are other tillage operations for weed
control. They improve the soil physical condition by breaking surface crusts
while removing young weeds.
Tillage is found to be more effective in controlling biennial and perennial
weed species than annual weeds, except in perennial weeds that propagate by
rhizomes (e.g., johnsongrass, quackgrass). In the latter cases, tillage exposes
these underground materials and reduces propagation of the plant.
5. Allelopathy. Allelopathy is the ability of some plant species to inhibit the growth
of other plants in their vicinity by exuding toxic chemicals into the soil. Rye
mulch has been successfully used to suppress weeds in no-till cultures of crops
like pea, corn, and cucumber.
6. Crop rotations. Crop rotation is the strategy of growing several judiciously
selected crops in a cyclical fashion on the same piece of land. By varying the
crops on the land, the growth of weeds is disrupted by the lack of consistent
favorable environment that favors them, since each crop has unique requirements.
The buildup of weed populations is limited by this cycling of crops.
7. Intercropping. Intercropping is the strategy of growing two or more crops
together on the same piece of land in one growing season. Because the crops
have different spacing requirements and morphological features, the ground is
more effectively shaded to restrict weed growth.
8. Mulching. Plasticulture is discussed in Chapter 20.
9. Herbicides. Synthetic herbicides are prohibited in organic production. However, a
number of preparations with low herbicide toxicity are permitted, including corn
gluten meal and herbicidal soaps. Commercial products such as WeedBan and
Corn Weed Blocker are available. Herbicidal soaps such as Scythe may also
be purchased by growers. Vinegar is a component of several newly released herbicides,
such as Burnout and Biorganic.
22.11 DISEASE AND INSECT PEST CONTROL
An effective pest management plan is rooted in an understanding of the biology of the pest,
including factors such as the life cycle, stage in the cycle it is most vulnerable, stage in which
it causes economic damage to crops, and method of dispersion. Pest control strategies are
discussed in detail in Chapters 7 and 8. Like nutrient supplementation, synthetic pesticides
are forbidden in organic culture. Consequently, preventive measures are relied upon in pest
management in organic production. Avoidance strategies include the use of pest-resistant
cultivars, sanitation, crop rotation, and timing of planting, among others.
22.11.1 TIER APPROACH TO PEST MANAGEMENT
Just like nutrient management, some synthetic products are allowable under some
circumstances. However, producers are required to first exhaust all avenues for using
physical, biological, legislative, and cultural methods of pest control, before considering
the use of approved materials. To this end, the NOP recommends that a pest management
plan be three-tiered, the distinction between the first two levels often being minimal:
Level One—This includes proactive management practices that reduce the potential
for the development of disease and pest (e.g., the avoidance measures).
Level Two—The management at this level includes the use of cultural and
mechanical measures (e.g., planting dates, cultivations, etc.).
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