Optimizing Organic Nutrient Sources

By Davie Kadyampakeni

The use of certified organic nutrient sources (manures, composts, biochar, biosolids, etc.) should be considered by Florida commercial citrus growers to improve the soil properties and long-term nutrient availability of the predominantly sandy soils. Use of the organic residues could be incorporated in the soil during tillage to plan a new grove or periodically to an existing grove to maintain or improve the physical, chemical and biological condition of soil and to minimize soil erosion.

Growers should manage organic nutrient sources to maintain or improve soil health in a manner that does not contribute to contamination of crops, soil or water by plant nutrients, pathogenic organisms, heavy metals or residues of prohibited substances. Safe products to use in fruit crops such as citrus include compost, biosolids or biochar. These products undergo various processes and have to pass consumer safety standards before being used in agricultural farms.

To ensure optimal efficacy of organic nutrient sources:

• Disk the compost or biochar in planting stations when establishing a new grove.
• Apply compost or biochar once a year to improve soil organic matter and organic nutrient content of the soil. A test of the compost or biochar nutrient content should be done to determine how much inorganic fertilizer needs to be added to meet the difference.
• Apply biosolids twice per year but check nutrient content to make sure those nutrients that are inadequate are supplemented with synthetic fertilizers.
• Since organic nutrient sources may contain nutrients that are released slowly, supplement them with soil-applied or foliar-applied macronutrients and micronutrients.
• Always keep an eye on the soil organic matter of your soil to see if it is increasing over time beyond the typical <2% of Florida sandy soils. An increase in organic matter implies an increase in soil water, nutrient retention and most of the soil health aspects of a grove.
• More importantly, conduct routine leaf tissue tests to ensure nutrient levels are optimal for high tree production.

Davie Kadyampakeni is an associate professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.

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