Horticulture Principles and Practices

22.8 MANAGING SOIL PHYSICAL QUALITY
A good farming soil should be maintained in a condition such that soil compaction and
erosion are reduced, while soil water-holding capacity, aeration, and tilth are enhanced.
Tillage and mechanical cultivation can be used judiciously to incorporate organic matter
and other soil organic amendments into the soil to improve its physical quality. Incorporation
of organic matter into the soil stabilizes soil aggregates and reduces soil erosion.
Practices such as crop rotation also maintain good soil physical condition since crops
vary in root depth and characteristics.
22.9 SOIL FERTILITY MANAGEMENT
Soil fertility management is one of the key activities in organic production. As previously
stated, one of the key foundational principles in organic production is the use of natural
plant nutrition.
22.9.1 NUTRIENT MANAGEMENT PLANNING
AND MONITORING
Just like conventional production, nutritional balance is important in organic production.
However, because of the more stringent production guidelines, nutrient management in
organic culture should be carefully planned and monitored to remain compliant with
NOP guidelines. The plan should include the approaches for using natural plant nutrition
through practices like crop rotations as well as incorporating nutrient amendment
and environmental protection from contamination. These should be detailed in the
OSP. Another key aspect of nutrient management is soil testing to monitor nutrient
concentration in the soil.
22.9.2 REPLENISHING SOIL NUTRIENTS
BY NATURAL PLANT NUTRITION
This approach to fertility management in organic production relies on natural cycles and
carefully planned human practices to replenish the soil with nutrients extracted during a
production cycle. Organic matter is incorporated into the soil to be decomposed by soil
microbes to release nutrients by the process of mineralization. The major practices for
natural plant nutrition are:
1. Green manures. Specific plants are cultivated with the sole purpose of
incorporating into the soil while green.
2. Cover crops. Cover crops are grown for the primary purpose of soil and nutrient
conservation. If leguminous, they can enrich the soil through nitrogen fixation.
Cover crops may be used as green manures. Examples of cover crops are
sunhemp (Crotalaria juncea), velvet bean (Mucuna deringiana), hairy vetch
(Vicia villosia), and crimson clover (Trifolium incarnatum). If an inoculum is to
be used for a legume species, it must be of the approved kind.
3. Animal manures. See book
4. Compost. General composting is discussed in Chapter 22. To be allowed for use in
organic production, composts must be prepared according to NOP guidelines. Raw
animal manure may be applied to crops grown for livestock feed but not for human
consumption. If applied to a crop whose edible portion does not touch the soil, it
cannot be harvested earlier than ninety days postapplication. If the edible portion
touches the soil, harvesting must be delayed until 120 days postapplication.
Municipal waste is prohibited from organic production. The carbon-to-nitrogen ratio
(C:N ratio) of the raw materials should be between 25:1 and 40:1. Further, the
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