Beans: leaves reveal nutritional problems

The characteristics of bean They can reveal important signs about the nutritional status of the crop. According to data released in the technical material presented, deficiencies in Nitrogen, Match, Potassium, Calcium, Magnesium, Sulfur Micronutrients can alter the color, shape, and development of leaves, impacting productivity.

Nutritional symptoms first appear in the leaves.

The common bean has a relatively short growing cycle and a root system that is sensitive to waterlogging and compaction. Problems such as excess or lack of water, high acidity, low organic matter, and very sandy or poorly managed soils can limit nutrient absorption.

According to data released in the technical material presented, soils without adequate acidity correction can reduce the availability of phosphorus, calcium, magnesium, and molybdenum. Sandy soils, on the other hand, present a greater risk of leaching of nitrogen, potassium, sulfur, and boron.

The deficiency can also be related to unbalanced fertilization, periods of drought, excessive rainfall, inadequate irrigation, and soil compaction. In many cases, the problem is not caused by a single factor, but by a combination of chemical and physical soil conditions, fertilization management, and climate.

New or old leaves help identify the nutrient.

The location of the symptom on the plant is one of the first things to observe. Mobile nutrients, such as nitrogen, phosphorus, potassium, and magnesium, tend to show deficiencies initially in older leaves.

This happens because the plant is able to remobilize these nutrients from older leaves to newer structures. However, less mobile nutrients, such as calcium, boron, iron, and copper, tend to show symptoms first in new leaves and at the growing tip.

According to data released in the technical material presented, changes in color, necrosis, deformation, reduction in size, and changes in leaf thickness and shine may indicate a deficiency. However, different symptoms may be similar, which requires confirmation by other methods.

Nitrogen causes older leaves to yellow.

Nitrogen is involved in vegetative growth, chlorophyll formation, and protein production. Although beans can obtain some of this nutrient through symbiosis with rhizobia, poor soils, nodulation problems, or high cultivar demand can result in deficiency.

The symptom first appears on the older leaves. The leaf blade shows uniform yellowing, starting at the tip and edges and progressing towards the center.

According to data released in the technical material presented, nitrogen-deficient plants tend to exhibit slow growth, short internodes, and smaller leaves. In severe situations, premature defoliation of older leaves occurs. The deficiency can reduce branch and pod formation, the number of grains per plant, and grain weight.

Phosphorus can darken the color of leaves.

Phosphorus is involved in energy metabolism, root development, and the formation of flowers and grains. In acidic soils, its availability can be reduced even after fertilizer application. Deficiency tends to appear first in older leaves, which may acquire a dark green or slightly bluish-green color.

In more advanced stages, purplish tones may appear on the edges or underside of the leaves, depending on the cultivar and environmental conditions.

According to data released in the technical material presented, phosphorus deficiency can also cause reduced growth, a poorly developed root system, and delayed flowering.

Potassium causes burning on the edges.

Potassium plays a role in stomatal opening, water balance, sugar transport, and stress resistance. Deficiency is common in sandy soils or soils with low cation exchange capacity, where there is a greater risk of leaching. Symptoms first appear in older leaves, mainly on the margins.

The yellowing of the edges evolves into necrosis, giving it a burnt appearance. The central region of the leaf remains green initially, while the edges may become dry and brittle in advanced stages.

According to data released in the technical material presented, the deficiency can result in reduced vigor, increased sensitivity to drought, weak stems, and reduced grain filling.

Calcium affects new leaves and shoot tips.

Because calcium is not very mobile within the plant, it mainly shows symptoms in new leaves, shoot tips, and other growing structures. Leaves may become deformed, wrinkled, and have irregular edges. The leaf blade tends to appear thicker and more brittle, with the possibility of chlorotic and later necrotic spots near the edges.

In severe cases, it can cause the death of the shoot tips, as well as the formation of weak branches and problems with flowers and pods.

Magnesium causes chlorosis between the veins.

Magnesium is a central component of chlorophyll and participates in several enzymatic reactions. Deficiency usually appears first in older leaves. The main symptom is interveinal chlorosis. The areas between the veins turn yellowish, while the veins remain green.

According to data released in the technical material presented, the problem may be more common in highly leached soils or those with an imbalance between calcium and potassium. In more severe cases, necrotic areas appear between the veins, reducing photosynthesis and productivity.

Sulfur causes the top of the plant to turn yellowish.

Sulfur is involved in protein synthesis and amino acid formation. Its deficiency can occur mainly in sandy soils and systems with low utilization of sources containing the nutrient. Unlike nitrogen, symptoms usually appear in the newest leaves.

The yellowing is relatively uniform and begins at the top of the plant. The veins also tend to yellow along with the rest of the leaf blade.

According to data released in the technical material presented, the plants become paler, with slow growth and short internodes, in addition to showing reduced vegetative and reproductive development.

Zinc reduces leaf size.

Among micronutrients, zinc deficiency first appears in young, already expanded leaves.

The leaves may become smaller, with shortened internodes and mild interveinal chlorosis. In more severe cases, whitish streaks may appear. The plant takes on a low appearance with small, narrow leaves, and may have a rosette shape.

According to data released in the technical material presented, the problem can delay flowering and reduce the number of pods per plant.

Iron causes severe yellowing of new leaves.

Iron deficiency initially appears in the newest leaves, mainly at the top of the plant. The characteristic symptom is intense interveinal chlorosis. The veins remain green, while the rest of the leaf blade turns yellow and can become almost white in severe cases.

According to data released in the technical material presented, soils with high pH, excessive liming, and certain situations of poor drainage can contribute to the problem.

Manganese leaves necrotic spots on leaves.

Manganese can also cause interveinal chlorosis, but it has an important additional characteristic.

On young leaves, but not necessarily the newest ones, small necrotic spots appear, similar to brown dots distributed across the leaf blade. The underside of the leaf becomes yellowish, and the small spots may intensify.

According to data released in the technical material presented, the deficiency can occur in soils with high pH, after very heavy liming, and in organic soils with high organic matter content.

Boron damages leaves and reproductive structures.

Boron is especially important for new leaves and reproductive structures. Deficiency can cause deformation of the tips, thick and brittle young leaves, cracks, or small necroses near the edges.

Leaf curling and distortion can also occur. According to data released in the technical material presented, malformed flowers, flower abortion, and problems with pod setting are among the effects associated with the deficiency. Sandy soils with low organic matter and prolonged periods of drought can favor the problem.

Molybdenum deficiency can be confused with nitrogen deficiency.

Molybdenum is related to biological nitrogen fixation and the metabolism of this nutrient in plants. Deficiency can cause widespread yellowing similar to that observed in plants with nitrogen deficiency.

According to data released in the technical material presented, the symptom can occur even when there has been adequate nitrogen fertilization or inoculation, especially when the nodules show low activity. Acidic soils and soils without adequate pH correction can reduce the availability of molybdenum.

Not every spot on a leaf is a deficiency.

Foliar diseases, such as anthracnose, rust, and angular leaf spot, can present symptoms similar to those of nutritional deficiencies. Damage caused by pesticide phytotoxicity can also lead to leaf changes.

According to data released in the technical material presented, the distribution of symptoms is one of the elements that helps in differentiation. Nutritional deficiencies can appear in bands or areas related to soil type, fertilization failures, or topography. Diseases tend to form patches and advance over time. The shape of the lesions should also be observed. Deficiencies generally produce more diffuse patterns, while diseases may present well-defined lesions.

How to confirm the cause of the symptoms

When noticing changes in the leaves, the first step is to check if the symptoms started on new or old leaves. It is also important to observe if the yellowing is uniform or occurs between the veins, as well as the presence of necrosis on the edges.

According to data released in the technical material presented, the area's history should be correlated with the symptoms. Soil type, liming, fertilization, previous crops, and drainage problems can aid in diagnosis.

Soil analysis should be consulted to check the pH and levels of suspected nutrients. When possible, foliar analysis can also complement the assessment. Confirmation should also consider the cultivar, the environment, and the intensity of the deficiency.

The stage of the culture also changes the impact.

The timing of the deficiency affects crop yield. According to data released in the technical material presented, severe deficiencies in the early stages can compromise the stand, the formation of productive branches, and the number of pods.

When the problem intensifies during the reproductive phase, it can cause flower abortion, pod malformation, shriveled grains, and a reduction in the weight of a thousand seeds. Therefore, early identification of symptoms can help guide management decisions.

Diagnosis should avoid decisions made solely through visual means.

The symptoms presented serve as indicators, but should not be used in isolation to define a nutritional correction. According to data released in the technical material presented, confirmation should consider soil analysis, area history and, preferably, foliar analysis.

Nutritional correction must follow technical recommendations, in addition to the label and package insert guidelines for fertilizers, and must be monitored by an agricultural engineer. Any intervention via soil or foliar application must also comply with current legislation and official technical recommendations.

Checklist for identifying bean deficiencies

When observing leaves with changes, the producer should first check whether the symptoms appear on new or old leaves.

It is also necessary to observe the pattern of yellowing, the presence of necrosis, and the location of the changes in the leaf blade.

The assessment should include fertilization history, symptom distribution across the plot, soil condition, and available analysis results.

According to data released in the technical material presented, differentiating between nutritional deficiency and disease or phytotoxicity is fundamental before initiating any corrective action.

Technical monitoring allows for defining the necessary measures for the current crop and also adjusting the management of future harvests.