because supply does not always match with demand:

Dry matter leaf analysis:

Fertilizer adjustments are usually based upon the results of soil, substrate or drain water analysis. Increasingly, the chemical composition of the plant itself is also being tested to examine not only the supply, but also the uptake of the plants.

When sampling

Leaves are usually being analyzed when deficiency or excess symptoms become visible. By comparing the analysis of the leaves with the target values it becomes clear if the absolute and relative levels of nutrients are sufficient or not. An inhibited growth without symptoms of a nutrient disorder can also be a good reason to analyze the leaves. Nutrient disorders normally become visible long after a deficiency or excess is actually being present.

Starting with a new crop or cultivar can also be a very good reason to examine the chemical composition of the leaves. When a new crop or variety is being tested, it is important to make sure the plant is actively growing, so we can be sure the uptake of elements is optimal. By analyzing the leaves regularly it can become quite clear how much of each element this plants really need. Based upon this information we can develop crop or cultivar specific fertilizer recipes with corresponding target values.

Dry matter or plant sap analysis

Principally there are two types of leaf analysis. Dry matter and plant sap analysis. The difference between these two methods is that the dry matter analysis includes all macro and micro nutrients, while the test procedures for plant sap analysis are limited primarily to test for the presence of nitrate, phosphate and potassium. Beside that most plant sap analysis are not entirely quantitative, but provide the user the qualitative “ yes” or “no” evaluations. While dry matter analysis are widely studied and provide on large scale quantitative target values. Because the dry matter method is scientifically more accepted, Relab den Haan only performs the dry matter method.

Procedure

The lifecycle of a plant leaf consist of different stages: synthesis, development, activity, storage and abscission. For the usage of the leaf analysis results, it is important to take into account that the chemical composition is under influence of the growing stage of the leaves. That is why it is necessary to collect the most recent mature leaves. When there are severe deficiency or toxicity symptoms it is sometimes useful to test just the affected parts of the plant.

Target values

For the interpretation of the results we have target values for almost every crop. These target values are mostly general and sometimes cultivar specific . Differences in nutrient composition between varieties are very common and can exceed 25%.

The table below shows the target values of macro nutrients of some of the main crops.



Just like substrate analysis it is not only important to evaluate the absolute values but also the relations between the nutrients. A high nitrogen : potassium ratio for instance can result in weak plant development, while the absolute levels of both elements are within the optimum range. And induced by the presence of high levels of zinc a sufficient level of iron is no guaranty that leaves remain green, because zinc can inhibit the iron activity.

Sending samples / More information

The sample must be dry and free of residues. Inform us when foliar feeding took place, so we can wash the leaves before the drying process starts. The minimum amount of leaf material necessary for a reliable analysis is 50 – 100 grams of fresh product.

For more information please contact Boris Berkhout at Relab den Haan.

Relab den Haan

Ing. Boris Berkhout (e-mail)
www.relabdenhaan.com














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