The leaf test is one of the most accurate methods for evaluating the plant’s nutritional status. In this method, by analyzing the concentration of nutrients in the leaves, the hidden deficiencies of the plant are determined before the appearance of symptoms.

The scientific method of the leaf test helps farmers and gardeners to make timely and targeted decisions about consumption with full knowledge of the real needs of the plant. The leaf test prevents the wastage of resources and excessive use of fertilizer, and by improving the health of the plant, it increases the quantity and quality of the product.

In this article, we have examined the importance and necessity of the leaf test, how to do it correctly, the right time for sampling, the principles of interpreting the results and the role of specialized fertilizers such as potassium sulfate in increasing accuracy and productivity.

Leaf test and analysis of its results

In the Berg test, the experience and skill of the person conducting the test plays an important role, especially in comparative diagnoses. One of the strengths of this method is the possibility of quick and low-cost analysis of fresh plant tissues. Therefore, it is possible to find out the nutritional status of the plant before the appearance of symptoms of lack of the required substance.

In this way, to check the lack of nutrients, plant tissue analysis is used to measure the exact amount of the desired elements in the leaves. The amount of nutrients in the soil and available to the plant directly affects their concentration in the plant organs.

If this concentration is lower than a certain level, the performance of garden products will decrease significantly. This range, which indicates the critical threshold, is known as the Critical Concentration Range (CCR), which is a reliable indicator in leaf analysis.

However, to achieve higher quality products, it is suggested to use the concept of Sufficiency Level (SL) instead of CCR. Sufficiency level is actually a range of nutrient concentration to optimize plant performance.

Normally, the amount of elements at this level is about 20-25% higher than the critical value. In simple terms, SL is the average range of concentration that is the optimum level of nutrients in leaves.

If the amount of a food element in the leaves is less than the critical range, the plant responds positively and economically to the application of that element in the form of fertilizer.

Simply put, if the amount of a nutrient element (for example, nitrogen, potassium or iron) in the leaves of the plant is less than the critical level, it means that the plant is deficient in that element. In this situation, if you give that element to the plant in the form of fertilizer, the plant will react positively to it; That is:

  • It grows better.

  • Product performance increases.

  • This increase in performance will be cost-effective and economical (because the cost of fertilizer is less than the profit obtained).

When the concentration of an element is very low, fertilizing is useful and economical; Because the plant needs it badly and by receiving it, it performs better. But if the concentration of that element exceeds the critical level; It means that the amount of a nutrient (such as phosphorus or nitrogen) in the plant is sufficient.

If you still give that element to the plant in this situation, it will not affect the performance of the plant, you have just paid more for buying fertilizer and it may even damage the plant or disrupt the absorption of other elements.

Time to do the leaf test

Determining the critical concentration of a food element in a plant leaf is not an easy task. Because this value is influenced by a set of different factors. Among these factors, we can mention the physical and chemical characteristics of the soil, yield level, type of plant and the final quality of the product.

In addition, external and internal factors such as air temperature, physiological age of the plant, soil moisture and even the balance between nutritional elements affect the final concentration of elements in the leaf. For this reason, choosing the right time for sampling is very important and should be done carefully.

Principles of leaf sampling

The common method for sampling is to take the last fully opened leaf. The desired nutrient can be measured through the analysis of different parts of the leaf, such as the petiole, the whole leaf, or the leaf blade.

Since the concentration of nutrients changes with the passage of time and the change of growth stages, the time of sampling should be chosen in such a way as to minimize these fluctuations.

Best time to sample

The best leaf test results are obtained when the plant is in the active growth phase.

In the case of fruit trees, about 2.5 months after the beginning of flowering is considered a suitable time for leaf sampling; Because during this period, the changes in the concentration of nutrients in the leaves are very small and the results of the analysis will be more reliable.

In the initial stages of growth or close to harvest time, the amount of nutrients in plants changes naturally. Therefore; Sampling in these intervals can lead to results that are difficult to interpret accurately.

Leaf test methods

1. Measurement of chlorophyll concentration in leaves

In this experiment, the amount of chlorophyll in the leaves is measured using a device called a chlorophyll meter. These data indicate the nutritional status of the plant, especially the amount of nitrogen in the leaves. The appropriate concentration of chlorophyll can indicate the general health of the plant and its ability to carry out effective photosynthesis.

2. Evaluation of physiological stability of leaves

In this test, the leaves are exposed to UV light and fluorescent colors to check the stability of their cell structure. If the leaves still show a suitable fluorescent reaction after light irradiation, this can be a sign of the health of the cell membrane and the physiological stability of the leaves.

3. Investigating the photosynthetic activity of leaves

To measure the efficiency of photosynthesis, the leaves are placed in controlled light conditions and the carbon dioxide concentration of the environment is measured. Then, using a photometer or gas exchange analysis devices, the rate of photosynthesis is evaluated. This test is an important indicator of plant productivity in dry matter production and growth.

4. Microscopic structure analysis of leaves

In this section, leaves are examined like biological samples to analyze their external (such as cuticle, stomata) and internal (clanchyma and parenchyma tissues) microscopically. This analysis provides information about the adaptation of the plant to the environment and its efficiency in light absorption and gas exchange.

Additional notes for interpretation of results

The standard tables that are provided to interpret the leaf test results are set based on sampling in the same period of time (about 2.5 months after flowering); Therefore, if the sampling is done at another time, the amount of different nutrients may be recorded, the interpretation of which requires more precision and specialized knowledge.

Since the interpretation method based on the critical concentration depends on many factors and has its own complexities, it is recommended to examine the results of the leaf test together with the results of soil and water analysis in order to make an accurate fertilizer decision.

Important points in leaf sampling to analyze nutrients

1. The time for leaf sampling is usually from mid-July to mid-August.

2. Leaves should be selected from branches without fruit, in their middle part and from fully grown branches. These branches should be at a height between 120 and 180 cm from the ground. Therefore, you should avoid removing leaves from very low branches or the end branches of the tree.

3. In species such as walnut that have compound leaves, it is better to take samples from the middle leaves.

4. In most cases, leaves are sampled from branches grown in the current season and the middle leaves of the same branches are harvested.

5. For leaf analysis, usually in each hectare of 2 to 3 trees, 10 leaves are randomly selected from different parts of the garden and analyzed.

6. In each garden plot, usually 10 to 20 trees are selected and 4 to 5 leaves are sampled from each tree. “Part of the garden” means a part of the garden that has a uniform and similar condition in terms of soil, type of variety, age of trees, watering and feeding methods.

7. If in recent days, the leaves have been sprayed with low consumption elements such as zinc, iron, manganese, copper or boron, they should not be sampled. The best case is that sampling is done before spraying.

8. If spraying or foliar spraying has been done, sampling should be done at least 10 days later so that the analysis results are not affected by those substances.

9. If signs of deficiency or poisoning are observed on the trees, sampling should be done separately from healthy leaves and leaves with symptoms.

10. Sample leaves should be in paper envelopes and be transported to the laboratory no later than 24 hours after sampling. If it is not possible to send immediately, the samples can be kept in the refrigerator for up to 48 hours. After reaching the laboratory, the samples should be dried in the shade and at normal ambient temperature.

11. It is recommended that this sampling be done every year in order to record the information related to the fertile and lean years and to obtain a more accurate analysis of the nutritional status.

12. Sampling should not be done after irrigation or heavy rain; Because it can cause fluctuations in concentration or dilution of elements.

13. On the envelope of the samples, full information such as the name of the garden or the gardener, the place of harvest, the state of fruiting of the tree and any additional information should be included so that the exact identification of the samples is possible.

14. When taking samples, it is better to have clean hands or use gloves so that dirt or skin oil does not affect the sample.

potassium sulfate; An effective supplement to improve the results of the leaf test

One of the important factors in achieving accurate and reliable results of the leaf decomposition test is the use of high-quality potassium fertilizers without chlorine. Potash Asia’s potassium sulfate fertilizer, with high purity and formulation according to international standards, is an ideal option for supplying the potassium needed by plants without causing salinity stress.

This product, by providing a balanced level of potassium and sulfur, both improves the nutritional indicators of the leaf and has a direct effect on the yield and quality of the final product.

Asian potash industry, the largest producer Potassium sulfate In the country, by using modern technical knowledge and new technologies, it has provided a safe and economical solution for professional farmers. Using this product along with detailed leaf analysis will be an effective step towards increasing the productivity and health of farms and gardens.

final word

The leaf test is an important method for the accurate management of plant nutrition, which informs the farmer about the actual nutritional status of the plant by scientifically analyzing the amount of nutrients in the leaves.

The correct implementation of this test at the right time, along with the expert interpretation of the results and the use of effective fertilizers such as potassium sulfate, can have a significant impact on the performance, quality and health of products.

Using this method, especially in orchards and sensitive crops, is an effective way to increase productivity, reduce unnecessary fertilizer costs, and achieve sustainable and scientific agriculture.