There are currently several ways to establish a correct balanced nutrition in plants and carry out a correct program, both foliar and soil nutrition. One of the most important antecedents that can be taken into account when making this type of decision is the foliar analysis carried out in the post-harvest period; but why in this period? The importance lies in the stabilization of the nutrients in the plant.
When talking about post-harvest, it is possible to think of an extensive period of time that for some varieties can even extend from November to March, or more; however, post-harvest refers, in this case, to the moment when the nutrients are stable in the plant and is not necessarily related to the stage in which the fruit is extracted from the plant. But a new question immediately arises. When are the nutrients stable in the plant? This responds physiologically to a period of great importance, which is the change in the reserve flow or the flow within the plant that occurs from the change of season from spring to summer, giving rise to the shortening of the photoperiod, an important sign of the pre-dormancy of deciduous plants. In other words, it is possible to establish theoretically that after December 21, the nutrients are already stable in the plant and if a study is carried out through a foliar analysis, it is possible to recognize this state through numbers that this foliar analysis provides for each of the nutrients.
What would happen then if the leaf analysis is performed before the aforementioned time?
“The result of the foliar analysis only reflects the moment in which the material was taken for foliar analysis. But it does not reflect whether the number indicated in this foliar examination is correct within certain ranges. Therefore, it is a photograph or an x-ray of the moment. If this nutritional foliar examination is carried out from December 20 or 25 onwards, it is possible to trust that this range provided by the laboratory is a range that is already established in the plant,” said Carlos Tapia, Founder and Technical Director of Avium.
Now, how is this leaf analysis carried out? There are many methodologies to learn how to carry it out, however, the most important thing, from a statistical point of view, is that the leaf sample perfectly represents the orchard or plot in which it is being taken.
“A sample composed of many plants should be taken at random, in which it is certain that it is a sample that represents the variety or the plot. Much has been said about which leaf sample should be taken, and in general the laboratories work quite well with 100 to 150 leaves per sample, considering that many of them leave a counter sample. It is important to take a leaf with a petiole and not just a leaf, since the petiole could also provide important nutritional information,” explained the Cherry Production Specialist Advisor., Carlos Tapia.
Which leaf should be collected? The leaf from the middle third of the annual shoot is recommended, although Carlos Tapia differs from this.
“Personally, I do not agree with the sampling of that leaf, because it is a new leaf that in general could have erroneous information about some nutrients and that could mainly travel through water, as is the particular case of potassium and calcium. Potassium in new leaves or in the leaves of the annual shoot will always be more present, because it is a water mobilizer, it has an important osmotic power. Therefore, perhaps it could give me erroneous information. Personally, I believe that the leaf that would best represent a nutritional status from the foliar point of view is the leaf of the two-year-old wood. That is, it is the leaf of the new shoot that is being formed. We have the annual shoot that is the leading shoot, the leaf of the wood immediately after that annual shoot is the one that should generally represent the nutritional status through this analysis,” the specialist warned.
What can be seen in a leaf analysis? Carlos Tapia explains in detail what to pay attention to when obtaining sample results.
“Personally, I would focus on some important nutrients, with some characteristics per rootstock. Number one, nitrogen, I think it is important and while it is an important indicator within the foliar examination, it is important to look at the plant and understand the nitrogen condition or the nitrogen range that the analysis is giving us. It happens a lot to us that we do a foliar analysis, the analysis tells us that the nitrogen is in the range of 1 percent, which is low within a standard, and we go to look at the patient and we realize that the annual growth exceeds 60, 70 or even 80 centimeters. Therefore, nitrogen is not necessarily important in the examination, but it could reflect what we are seeing in reality.”
Tapia warns that it is important to take into consideration the different rootstocks, taking into account their vigor, since the reference values vary.
“For vigorous rootstocks, the potassium status is very important, and we should recognise ranges between 2 and 2.5 percent. However, in vigorous rootstocks this range is always lower and is a very important indicator that vigorous rootstocks or very vigorous orchards are generally in short supply with potassium. In the case of magnesium, which is very important for Mahaleb and Pontaleb rootstocks and their more practical evolution over the last decade, the entire MaxMa series, the two best known to us in this series, MaxMa 14 or MaxMa 60, the magnesium status is very important. It should be above 0.5 parts per million and in general they have a hard time reaching 0.5 parts per million.” explained Carlos Tapia.
Now, in the case of the entire Gisela or acid series, which are lines of acidic sour cherry trees or direct descendants of acidic sour cherry trees, or often selections of acidic sour cherry trees, the status of Zinc is very important.
“Ideally, it should be above 40 parts per million and in practice we are seeing that in general, this type of rootstock or rootstocks of less vigorous series, are below these 40 parts per million. It is important to establish these differences, today we are talking about rootstocks that we believe is a very important advance and we are moving away from talking about the species itself,” explained the Founder of Avium.
What test should I ask for? Complete foliar nutritional test or analysis, which in some cases is important to include boron. Keep in mind that in the laboratories that exist today in Chile, where this type of analysis can be done (6 or 7 in total), it is enough to simply request a complete foliar nutritional analysis, so that they can provide all these ranges, that is, the complete analysis.
Not necessarily taking into consideration the ranges provided by some of these laboratories, which although well supported by previous research, today we believe that in Chile we have much more limited ranges, including, as previously noted, by rootstocks.
Foliar analysis is essential for making nutritional program decisions, especially for the recovery of nutrients from orchards after harvest.
