Foliar Nutrition in Macadamia Tree Nut Production International Macadamia Symposium - Brisbane September 2012 Mathur, Dr. Deepak Mathur, Ph.D. Director: Technical Services, Agrichem 4 Hovey Road, Yatala, Qld 4207, Australia Yatala,
Production constraintsLimiting NutrientGeneral aspects of foliar nutrition 1. Stomatal role 2. Pathways 3. Dynamics & Efficiency 4. Stage specific nutritionFoliar nutrition in Macadamia
Global Constraints: Agricultural Production Systems •Limited irrigation water supplies •Nutrient use efficiency •Diminishing Micronutrient pool •Rising salinity •Problem soils •Water Quality issues •Environmental issues •Global food shortage FAO: WE MUST DOUBLE FOOD PRODUCTION BY 2030
• Justus von Liebig•His laws reformed agriculture “Whichever nutrient is in the least amount relative to therequired amount, will determine the yield of a plant”
Foliar feeding is a technique of feeding plantsby applying liquid fertilizer directly to theirleaves. Nutrients are absorbed through theleaf cuticle.The cuticle is the outermost layer of the leafthat consists of epicuticular wax and isnegatively charged due to the presence ofpolygalactouronic acid
Improves YieldRestores tree healthImproves canopy growth after pruningFoliar-applied calcium, boron, copper, and zinc, used alone or incombination, have been shown to enhance acclimation or repair of stress-injured tissues.Further understanding of the oxidative stress may offer new approachesfor the use of foliar-applied nutrients on perennial fruit plantsFoliar applied nutrients create a negative osmotic pressure within the leaftissues that triggers roots to absorb more water from soil. As a result theroots also absorb soil applied nutrients that moves en masse with water.Hence foliar nutrition also improves the efficacy of soil applied nutrients nutrients.Maximum impact of foliar sprays can be seen under: Adverse Soil Conditions Low Nutrient Availability in soil through adverse interactions such as calcium and phosphorus
Stomata, the tiny leaf openings on the upper andlower surfaces of the leaf, do not play any significantrole in the absorption of foliar nutrientsThe mechanical force of pushing water vapor outthrough the process of transpiration restricts theentry of nutrients through stomataThe night time foliar nutrient uptake exceeds theday time absorption through leaves as demonstratedby radio isotope studiesPlants are also able to absorb nutrients through theirbark and bark does not contain stomata.
Foliar nutrition application goal: ◦ Increase duration of leaf wetness to increase availability of elements ◦ Increase cation movement through leaf cuticle Increased Wetness Movement Movement Movement Movement Increased Increased Increased Increased Mn Mn Mn Cation Cation Cation Cation Mn Mn Mn Mn Mn Mn Without Surfactant With Surfactant
MovementCoverage, Limits at Cuticle & Cell to Cell inDeposition, the Stomates Movement Conducting Wetting Membrane Tissues
E= Stage x Time x Combination x RatesWhere, E is the efficacy of spray product S is the crop stage T is the time of the day C is compatibility of nutrients R is the rate of application Droplet size and distribution Surfactants use Maximum impact Nutrient is deficient Low soil temperature Decreased root activity Caution: Do not spray a water stressed crop
Spring Flush Tissue test and then apply NPK+ TEproduct (Fe)3 weeks Pre-Flowering: N, B, Ca, Mg, ZnNo Foliar Sprays at Flowering: Flower dropTissue test recommended: Post floweringNut set- Ca, B, Zn, Mg+ High auxin/cyt kelpEarly Nut fill- K, B, Mg, FeLate nut fill- K, Mg, CaTissue test after 85-90% pickPost harvest- N, Ca, Mg, B, K, FeFoliar compliments soil applied ferts.