Continued from last month: A simple leaf test before flowering can make a huge difference to profitability. Here are 10 reasons why every grower should leaf test on a regular basis.
5 To monitor levels of ‘the big four’
American consultant, Gary Zimmer, has determined that achieving and maintaining luxury levels of four minerals, according to leaf analysis data, is a key to achieving maximum productivity with minimum strife.
These four minerals are calcium, magnesium, phosphorus and boron. All four minerals are intimately involved with photosynthesis—the most important process in plant production—and they comprise two synergistic pairs.
Boron is a huge player in calcium performance and magnesium stimulates the uptake of boron. Thirty-five per cent of all of the leaf tests we analyse are deficient in all four of these minerals and it is an extreme rarity to ever see all four at luxury levels.
The game plan is to lift the levels of these key minerals and this involves a precision approach involving high analysis mineral inputs with no tag ons.
What is the use of calcium nitrate to lift calcium, for example, if you already have far too much nitrate nitrogen (as is so often the case)?
Similarly, why select magnesium sulphate to boost magnesium, when you already have excess levels of sulphur?
We have found that micronised mineral suspensions—involving liquid fertilisers containing suspended particles of miniscule size—can be tremendous tools in achieving the elusive luxury levels we are seeking.
Lime-Life™, for example, contains 40% calcium compared to just 18% in calcium nitrate and it doesn’t contain any unwanted extras.
Similarly, Mag-Life™ contains more than double the magnesium than magnesium sulphate in a far more stable form.
The problem with this exciting, yield-building strategy is that it is not that easy to achieve. We have found that all movements in the right direction will prove beneficial but you will need regular leaf tests to monitor your progress.
6 To check that potassium is present when it is most needed
In this instance conventional leaf testing is not the tool of choice.
Potassium is the most mobile of all minerals and it often moves from the lower leaves to the top end of the plant, where it is required to size fruit or fuel growth at the growing shoot tips. Hence, the leaf sample, typically selected from the last fully developed leaf, can often reflect K levels in the region to which potassium has moved, rather than supplying an accurate indication of overall potassium status.
By the time the potassium deficiency has extended up to the zone you are measuring, you often have a serious shortage which will prove costly in the final analysis.
The Horiba Potassium Meter is an invaluable tool to avoid these costly oversights. It is simply a matter of measuring the lower leaves and upper leaves and K levels should be the same at both sites.
The moment the levels in the lower leaves are more than 10% lower than the upper leaves, you have detected a potassium shortage and should act immediately.
You will be amazed, if you adopt this approach, to realise just how strong the potassium draw-down can be when the plant enters the reproductive mode. You will also be surprised to observe the powerful antagonistic effect of excess nitrate nitrogen on potassium availability.
Nitrates, when oversupplied, will shut down potassium faster than a house cat will claw the knee upon which it sits, at the sound of a fridge door opening (dogs are a lot less fickle!).
7 To see that you maintain enough silica for cell-strengthening protection
Silica is becoming the hot ticket item for Ag science researchers.
This neglected mineral, which was previously considered a ‘non-essential’ nutrient, is now known to be a major star in pest protection.
It is also an important player in photosynthesis, stress resistance, heavy metal management, sodium tolerance and nutrient delivery.
While there have been no ‘ideal’ leaf levels determined for most crops, we have been able to determine general performance zones based upon observation and grower reports.
Recently a NSW blueberry grower reported sensational shelf-life for his produce when his leaf levels of silica were at 1200 ppm.
When he neglected his regular silica applications and leaf levels fell to just 300 ppm, so did his fruit quality. The shelf-life was a fraction of the original but began to improve as soon as he resumed his applications of Dia-Life™ which is based upon micronised diatomaceous earth which contains 85% silica dioxide.
We have found that small, regular applications of this suspension via fertigation, results in substantial increases in the levels of silica in the leaf.
8 To avoid the undesirable build up of copper in the plant based on abuse of copper fungicides
Continued next month
For more information, see Tree Fruit January 2014
