The importance of Leaf Testing
There is an old saying that "seeing is believing" but in the case of plant nutrient deficiencies, seeing is usually too late.
To realise the full potential of modern, high yielding crops, balanced plant nutrition is vitally important. In order to grow and develop, plants need a constant supply of numerous mineral elements. A deficiency of any essential single nutrient is often enough to limit yield.
Visible nutrient deficiency symptoms do not need to show themselves in a crop before yield and quality losses can occur. In most cases, treatment of visible deficiencies takes place too late to avoid some loss in yield and quality. A crop showing no signs of visible deficiency does not always mean that nutrition is adequate. "Hidden hunger" is the term used to describe loss in crop performance, quality or productivity, even though no visible symptoms can be seen. They can also be described as marginal or sub-clinical deficiencies.
Plant tissue analysis is an essential way of evaluating the success of your fertilizer programme, as it integrates all the factors that have interacted to affect plant growth and development. It complements soil testing by measuring the nutrients actually taken up by the plant. Whilst a soil test is very important in determining the pH, CEC, nutrient levels etc, upon which to base your early season solid fertilizer programme, it doesn't take into account what interactions could occur during the growth cycle to inhibit nutrient uptake e.g.
• Wet, cold conditions (possibly causing lockup of elements such as zinc, manganese, and magnesium)
• Light soils (prone to leaching)
• Nutrient mobility
• Excess of one or more nutrients limiting the uptake of other key nutrients
In other words, the plant tissue test represents the effects of not only soil nutrient status, but also all the factors controlling plant growth.
Copper deficiency, as an example, can often be quite difficult to detect visually in a crop and yet it can possibly cause a dramatic yield reduction in crops such as wheat. The application of nitrogen will usually result in a copper deficiency becoming even worse.
Micro-elements such as copper, manganese, and zinc are required by the plant in much lesser amounts than the Macro-elements such as NPK, but this in no way diminishes the importance of trace elements in helping to achieve optimum crop yield and quality.
The message is clear, micro-nutrition is fundamental to a successful crop and if farmers are to make the most of their investment in other areas such as "new chemistry" and not limit its potential, trace elements must be a first consideration and not an optional extra.
Foliar applications, especially of trace elements, can be very beneficial in quickly and efficiently addressing a nutrient deficiency:
• Bypasses availability problems from the soil
• Nutrients are immediately available for plant use
• Allows more precise timing
• Easy integration into farmers spray programme
• Complimentary to your soil applied fertilizer programme
Phosyn is a world-leading manufacturer of high specification quality products, with over 30 years international experience in the nutritional field, including extensive trial work in arable crops.
Author: David Spencer, New Zealand
Published: July 2001