In
organic crop production, natural sources of fertility are used to
provide crop nutrition.
There are many sources available to organic
producers including animal manures, incorporated legume cover crops,
mined nutrients such as potassium, as well as commercially formulated
blends of nutrients.
The number of fertility products with guaranteed
nutrient analysis has increased in recent years. These newer products
take some of the guesswork out of calculating application rates and
reduce the risk of under- or over-application of nutrients; nitrogen and
phosphorus in particular.
Soil
quality is an important consideration on organic farms. Although the
definition of a “quality soil” varies by location, most researchers
agree on what parameters should be included. Minimally, a quality soil
is one that is chemically balanced, biologically active, and is
structurally sound.
Producers interested in assessing the quality of
their soil should refer to the database of alternative soil testing labs
listed below.
Many
of the nutrients present in organic soil amendments must be transformed
by soil microorganisms before they can be utilized by crops.
Therefore,
the soil environment must be suitable for these organisms to facilitate
efficient nutrient cycling. Tillage, excessive moisture or drought and
lack of carbon-based amendments are detrimental to soil carbon stores
and deplete the energy reservoir needed by microorganisms.
A suitable
soil environment is also important to support a variety of predators and
parasites of insect, diseases and nematode pests that dwell in the
soil.
Crop
nutrient management programs in organic systems are ultimately
site-specific. There is no “cookbook” approach to designing an organic
fertility program. Producers are advised to follow University of Florida
fertilizer recommendations.
One caveat to this is that organic
fertility sources release nitrogen slowly. Because of this, many
producers preplant incorporate the full nitrogen rate at the beginning
of the season for crops that mature in 60-70 days.
Maintaining
good records of irrigation, soil amendments, timing, rate and method of
application of inputs and crop response will provide a history to which
management programs can be fine-tuned. Producers should not
underestimate the value of a good crop and soil nutrient monitoring
program.
Experience is the best method to determine what works best to
produce optimum yields while maintaining soil and water quality.
