Prepare for Heat Stress

May 21, 2018

A key limiting factor for Florida citrus production and quality is heat stress. Management factors that can minimize the detrimental impact of heat stress are root system quality and quantity, irrigation management, and potassium nutrition. Action strategies for improvement can often be identified with a soil analysis, water analysis, and visual inspection of the root system.

Considerations for root system quality and quantity:

Soil chemistry dramatically influences total nutrient uptake as well as the development of the root system. Two considerations for soil chemistry are calcium availability for root-tip development and phosphorus availability for root development and plant energy. The soil chemical composition tends to take on the chemical characteristics of the water applied.

A soil and water analysis can identify opportunities for inputs and strategies that will be most beneficial.

Soil biology is critical for the root system development. The four keys to improved soil biology are:

  1. Optimum soil chemistry
  2. Ideal air:water relationships
  3. Promotion of optimum root growth
  4. Soluble carbon inputs

Considerations for irrigation management:

Few groves in Florida have trouble getting water into the soil. However, lateral movement and adequate air:water relationships in the root zone are critical. To the extent possible while maintaining optimum conditions, longer and less-frequent irrigations will be best. A comprehensive calcium management program will aid in improved soil air:water relationships.

Considerations for potassium nutrition:

Potassium is responsible for water and nutrient movement in the plant. It also regulates key enzyme production in plants. Often, citrus trees that stress readily from heat are deficient in potassium. Verification can be made by visual stress observations, a soluble paste extraction soil sample, and tissue analysis. The keys to improved potassium nutrition are:

   - Timing - Because potassium fertilization can be so beneficial, care should be taken to not offset other nutrients such as calcium and magnesium by untimely applications. In addition, light and frequent applications will be most likely to provide optimum response.
   - Input Selection – Four key considerations are:
        1. Solubility – How well does the material convert to K in the ionic form?
        2. Anion load – Is it beneficial for citrus production?
        3. Complexing – Is there anything done to the material to minimize undesirable reactions on the leaf and in the soil?
        4. Plant response – How well does the citrus respond with an application?

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