Post-harvest nutrition for kiwifruit
The leaf is the photosynthetic part of the kiwifruit vine that manufactures sugars, which are utilised by the plant to grow and to mature its fruit. It is important that leaves be kept on the vine as long as possible after harvest so that root growth is not limited. Early leaf fall can reduce root activity and therefore reduce consolidation of nutrient reserves in the plant, which could disadvantage the vine for the following season.
Improve Bud Development and Bud Strength
A foliar application of nitrogen post-harvest can improve bud development and bud strength in the following spring resulting in a stronger and more fertile bloom. A post-harvest nitrogen application won´t promote excessive vegetative cane growth the following spring, which a spring application of nitrogen can do. It is important to use a form of nitrogen that is totally safe to the kiwifruit foliage as premature defoliation of the leaves reduces the translocation of nutrients back into the cane.
Safe-N is a liquid controlled release nitrogen containing 35% w/v nitrogen. 70% of this nitrogen is in a controlled release form, with the remainder as quick release, low biuret urea. It is designed to maximise crop safety, nitrogen utilisation to the plant and have ease of handling for the operator.
No existing foliar nitrogen can compare to the efficiency and crop safety of this unique, patented formulation. Because Safe-N contains a complex series of organic nitrogen molecules it will not burn, crystallise on the leaf or lose nitrogen to the atmosphere through ammonia volatilization.
After application the majority of Safe-N can be found in the leaf in 6 to 8 hours and essentially it is all absorbed in 24 to 48 hours. 30% is available immediately and the controlled release component will remain in more complex forms until the plant can break them down over a longer period. Therefore Safe-N will feed the vine for longer and nitrogen losses are minimised. Apply Safe-N post-harvest and before leaf senescence.
Sufficient Nutrient Levels Necessary
As well as nitrogen, sufficient micro-nutrient levels of zinc and boron are particularly important early in the growing season to aid flowering and fruitset, the movement of sugars, and the function of many enzymes. Adequate zinc and boron levels are also essential as they can aid the mobility of calcium, a critical nutrient for improving storage potential and quality.
Post-harvest application of magnesium can delay leaf senescence and maximise nutrient remobilisation. This application is important where leaf magnesium levels are low or visual deficiency symptoms are apparent.
Bud Builder has been specifically formulated in answer to grower requests for a "one-shot" spray. Where magnesium, boron and zinc are all required, Bud Builder will supply all three nutrients plus phosphorus in an easy to use wettable powder formulation.
In kiwifruit, Bud Builder would typically be applied in the spring before flowering, however if low levels of these nutrients have been reported in leaf tissue, fruitlet or fruit analysis a post-harvest application should be considered.
Now there is no need to be weighing or measuring separate products as Bud Builder is available in a 10-kg pack and is recommended at 10-kg/ha. Bud Builder, at the 10-kg/ha rate, will supply 27% more magnesium than the standard rate of Hydromag and 40% more zinc than the standard rate of Zintrac. Bud Builder can be applied at no extra cost than Hydromag, Bortrac and Zintrac at equivalent rates and has all the nutritional advantages of these well established products. Zintrac, Bortrac or Hydromag can still be applied instead of Bud Builder where there is a need for only one or two of the nutrients.
The Importance of Analysis
Analysis is very important as it helps identify your nutrient problems and ensures you obtain the right products to maximise both quality and yield of your crop. Megalab interpretation is a free Internet based service available exclusively from Phosyn to give their customers precise recommendations from leaf tissue, fruitlet and fruit analysis in kiwifruit.
Author: Michael Waites, New Zealand
Published: April 2001