Highlands County Extension

Gregg Hartt Citrus Agent I Highlands County Extension 4509 George Boulevard Sebring, Florida 33875-5837 Voice - 863-402-6540 FAX - 863-402-6544 SUN - 718-6540 Email – wghartt@ifas.ufl.edu

Irrigation Scheduling: Maximizing Production Efficiencies While Minimizing Citrus Production Costs

Irrigation Considerations Crop use requirements Seedy Seedless Rootstock Variety Crop load

Irrigation Considerations Soil texture & profile Rainfall frequency and quantity Temperature, humidity, and wind Evapotranspiration rate Efficiency of irrigation system

Irrigation Considerations Soil moisture depletion Irrigation maintenance Permitted quantities Ag Mod in SWUCA II Leaching Development stage of crop

Irrigation Considerations Varietal differences in water use requirements Citrus needs about 47 acre inches per year to grow a crop During the spring flush the soil moisture should not be allowed to fall below 2/3 available water (AW) and this level of moisture should be maintained until the fruit is at least 1” in diameter. AW is the difference between field capacity & wilting point

Irrigation Considerations AW for sands & fine sands is averaged at ¾” Sandy & fine sandy loams averages 1.25” of AW Very fine sandy loams to silt clay loams average 1.5” AW Silt clay to clay averages 2” AW Peats & mucks average 2.25” AW

Irrigation Considerations Seedy varieties need less water than seedless varieties Rootstock February thru June is the critical irrigation period for fruit set Over irrigation in the fall can reduce fruit solids Tree age and size

Florida Automated Weather Network (FAWN) Air temperatures @ 2ft., 6ft., & 30ft. Soil temperature @ 4” Rainfall Dew point @ 30 ft. (estimated value) Relative humidity Wind speed Wind direction Solar radiation

FAWN Management Tools Irrigation scheduler Young trees Mature ridge Mature flatwoods Based on an 80% efficiency of system Wet bulb irrigation cutoff Minimum temperature estimator calculated at sunset

FAWN Management Tools Archived weather data Reports Latest readings Graph data Chart data Chart historical data Latest observations for each station in table format

Mobile Irrigation Lab Joint service provided by the Water Management Districts and NRCS Evaluates the efficiency of your irrigation

Mass Flow Considered to be the most important mode of nutrient uptake Relates to the movement of soil water towards the root surface The nutrient uptake through this mechanism is directly related to the amount of water used by the plants (transpiration)

Mass Flow Responsible for supplying the root with much of the plant needs for nitrogen, calcium, and magnesium, but does not do so in the case of phosphorous or potassium Largely dependent on the moisture status of the soil and is highly influenced by the soil physical properties controlling the movement of soil water

Diffusion Ions in the soil move from a point of higher concentration to a point of lower concentration Enables the movement of nutrient ions without the movement of water. An adequate supply of water in the soil is essential for nutrient solubilization. This mechanism is predominant in supplying most of the phosphorous and potassium

Rootstock Drought Tolerance Cleopatra Mandarin – intermediate to good Swingle Citrumelo – poor to intermediate Carrizo Citrange – good Volkamer Lemon – good Rough Lemon – good Smooth Flat Seville – good Sour Orange – intermediate Sun Chu Sha – intermediate to good

Soil Series Astatula Wholly within the ridge part of the state Very similar to Archbold, Candler, Orsino, Paola, St. Lucie, and Tavares Moderately sloping, excessively drained, droughty soils Soil reaction ranges from very strongly acid to slightly acid Sand to fine sand to a depth of 80” or more

Soil Series Immokalee Nearly level, poorly drained soils Found in broad areas of the flatwoods Very strongly acid Very similar to Basinger, Felda, Myakka, Pomello, Satellite, and Smyrna Pomello and Satellite soils are better drained than Immokalee Sand; single grained; loose