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.