Post-harvest fruit tree nutrition
Apples, Pears and Stone Fruit
The application of foliar nutrients to fruit trees post-harvest, in conjunction with the traditional NPK soil fertilisers, can be necessary to achieve a healthy crop which optimises yield potential and quality. Heavy crop loads place greater demand on the tree up until harvest so assisting the accumulation of essential nutrients for next season is vital to build strong flower buds and healthy leaves. Once the fruit has been harvested, the tree is concerned with building its reserves for the following season. Nutrients in the leaf are drawn back into the buds where they are stored in reserve for next season's demand.
Sufficent 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.
There is little or no uptake of nutrients from the soil in the early part of the season, as the supply from the roots only starts once extension growth has commenced. Concentrations of zinc and boron within the tree fall as leaves and flowers are produced, which means it is critical to ensure sufficient nutrient reserves in the buds before spring growth starts.
Post-harvest application of magnesium can delay leaf senescence and maximise nutrient remobilisation. This application is important where leaf magnesium levels are low and visual symptoms are apparent.
Bud Builder from Phosyn has been specifically formulated in answer to grower requests for a "one-shot" post-harvest 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. 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.
Safe-N - A foliar application of nitrogen post-harvest can improve bud development and bud strength in the following spring. It is important to use a form of nitrogen that is totally safe to the foliage as premature defoliation of the leaves reduces the translocation of nutrients back into the buds.
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 remains in more complex forms until the plant can break them down over a longer period. Therefore Safe-N will feed the tree for longer and nitrogen losses are minimised.
Apply Safe-N post-harvest and before leaf senescence at 5 to 10 ltrs/ha.
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 and apple fruitlet analysis.
Author: Michael Waites, New Zealand
Published: March 2001