Hortus - Complete Plant Nutrition

The principles of crop nutrition do not vary from crop to crop. All crops need the same essential elements. The difference between crops is that they need those essential elements in different ratios, different amounts, and at different times. Even the same crop has changing needs.

In what follows, wine grapes have been chosen as an example in order to elaborate what “Integrated Nutrition Management” (INM for short) is all about. This is not to say that the concept is not applicable to table grapes, apples, cotton, or the humble peanut. The principle is exactly the same. Wine grapes have been chosen perhaps because they are an “easy” example to elaborate the issues concerned.

Two wine grapes varieties grown on the same paddock, by the same grower, under identical conditions, may have different targets. On one variety, the grower is expecting to get a high Baume (sugar and solid contents), while on the other one, he is targeting for a darker colour. Such a case necessitates 2 distinct feeding programmes, even though both crops are grapes, and even though they are grown on the same soil and under identical conditions. Admittedly, not too many crops can offer such a case scenario.

“Integrated Nutrition Management” is a technique that allows us to address such cases.

Various factors are involved in determining wine grape quality. They include area, type of soil, irrigation practices, disease control, weed management, pest management, variety, rootstock, etc...

Nutrition however can also play a major factor in targeting certain quality criteria.
The purpose of this publication is to shed some light about advances in nutritional diagnostic skills and products and which can be of major significance in targeting quality issues.

History
Nutrition is often overlooked as a quality-seeking tool probably because traditional practices have not been able to address those quality issues.

Historically, soil and tissue analyses have mainly attempted to diagnose deficiencies, and at best solve those deficiencies by using corrective applications. Quality in itself was rarely addressed.

The tools used were soil and tissue analyses. From a practical point of view, analytical data are however as good as the practical recommendations that come out of them. Those recommendations, in turn, are dictated by the standards of judgement.

The traditional methods relied heavily on the so-called Critical Levels (or Critical Ranges) of minerals. The Critical Levels are crop specific. They are determined by comparing yields of a specific crop, having all other variables fixed, and varying only the levels of the mineral the Critical Level of which is to be determined.

The limitations of this approach are many:

INM distinguishes between simple targets (such as solving certain deficiencies) and market dictated targets (such as specific quality issues).

Like other techniques, INM employs soil and leaf analyses, but with many big differences. The interpretation of the analysis data is based on an integrated approach rather than one mineral at a time. The ratios of each mineral to every other mineral, as well as the individual absolute level of each mineral, are taken into account to reach a computer generated prediction of specific hypothetically ideal figures for each and every mineral given any situation. This is a true and unique approach in attempting to attain proper nutritional balance. INM believes that to reach certain quality targets, it is not enough to solve nutrient deficiencies and to even attain the proper balance. Some deficiencies may have no bearing on yields and/or quality. Others may even be favourable to produce a certain flavour quality. Sufficiencies of a certain mineral, on the other hand, may not be good enough to produce the quality target sought. To elaborate using a classic case, let us consider Nitrogen. Good quality grapes (again as an example) go hand in hand with Nitrogen stress towards maturity. Inducing N-stress can improve quality. A tissue sample in this case will reveal N-deficiency, yet N is not recommended. In a similar but reversed manner, certain mineral levels have to be pushed way beyond sufficiency levels in order to reach certain quality targets (such as colour, Baume, etc...). INM employs this technique not only with Nitrogen, but also with every other mineral taking into account its absolute as well as its relative level. INM acknowledges that the quality criteria demanded by the market do not necessarily have to match the physiological need of the plant as revealed by traditional yield-based approach of interpreting the analysis data. I.N.M. therefore interprets the data from the vantagepoint of the specific target of the grower. It is therefore able to determine what minerals are deficient, which are sufficient, and which are in excess from that very specific point of view; not from any other one. Given the same set of analytical figures for the same crop but at different situations (either in terms of stages of growth and/or different targets) INM will give 2 distinct interpretations. The recommendations produced by INM are based on the facts given above. They include soil preparation, base feeding, fertigation, and foliar feeding. They are simple to follow and implement, and extremely explicit and specific to the actual target. The target could be high yields, but it could also be a quality issue. It could be longer shelf life, better colour, better taste, evenness in size, etc...