Corn plants have simple needs, just give them heaps of water, sun, nutrients, and other corn plants and they are perfectly happy. But if your crop starts to look unhealthy, there could be a multitude of complicated problems at the root of the issue. Luckily, the solutions are readily available and easy to implement.
Start by identifying the cause of the problem, and you’ll be on your way to fresh corn on the cob in no time. This article dives into the sweet world of corn growing, including what causes yellowing leaves on corn plants, and how to fix it!
Why Does My Corn Plant Have Yellow Leaves?
Yellowing leaves are an important first sign that indicates there is a problem with your corn plants. The discoloration is called chlorosis and it happens when certain environmental conditions cause the plant to produce inadequate amounts of chlorophyll. Since chlorophyll is what makes plants green, they appear pale or yellow after chlorosis occurs.
Chlorosis can be caused by several different factors, including, leaf spot and rust diseases, leaf blights, or damage from pests. All cases of damage from bacteria, fungi, or insects should include evidence of actual leaf damage from the infestation along with the presence of yellowing leaves.
Yellowing leaves can also be a sign of damage caused by improper herbicide or fertilizer applications. All these issues are best found through early detection efforts to implement the solutions in time to save crop production for the season.
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Cause of Yellowing Leaves on Corn Plants & How to Fix
Of the many reasons that corn plants can have yellowing leaves, the most common causes are inadequate watering, nutrient deficiencies, rapid corn growth syndrome, and fertilizer burns. If caught and rectified quickly, these problems are easy and economical to fix in small fields.
The following breaks down each issue with methods of diagnosis and solutions.
Inadequate Watering
Keeping to a consistent watering schedule is important in maintaining the health of your corn plants. Continually over-watering can lead to root rot, while repeatedly under-watering can lead to leaf curl. Both of which can be indicated by the presence of yellowing leaves.
Over-Watering
While corn plants need a lot of water to produce healthy ears, they can only survive if there is also air in the soil. After 48 hours of saturated soil due to over-watering or rainfall, the oxygen that is normally taken up by the plant roots is completely depleted.
If this prolonged saturation occurs during periods of temperatures cooler than 65°F, then the plants have a greater chance of surviving than if the temperatures are 75°F or warmer.
Under-Watering
Corn plants need a total of 1/3 inch of water per plant per day during their time of highest water needs. A lack of water can stress the corn plant to the point that its leaves start to roll and turn yellow. When this happens its crop production capabilities are severely diminished. Roots also begin to die and cause nutrient deficiencies. To prevent this issue, check the soil moisture weekly and monitor for any signs of wilting.
Nutrient Deficiencies
Nutrient deficiencies can lead to a host of problems including stunted growth, poor seed production, and discoloration of foliage. Necessary nutrients such as nitrogen and potassium are the most common culprits of yellowing leaves but can also be caused by a lack of sulfur, magnesium, and zinc.
These deficiencies can be treated with a properly and consistently applied fertilizer regimen. For the health and safety of people and the environment, make sure to follow all guidelines set forth by the manufacturer.
Nitrogen Deficiencies in Sweetcorn Plants
Nitrogen deficiency appears on corn leaves as a yellowing V-shape that begins at the leaf tip and continues toward the base of the leaf. These symptoms will begin on older leaves at the bottom of the plant and progress upwards as the deficiency worsens.
Nitrogen deficiency can be caused by poor soil conditions, nutrient leaching after heavy watering or rainfall, and inadequate fertilization schedules. Nitrogen deficiency is more likely to occur during the later stages of growth when its uptake needs to increase.
Potassium Deficiencies
Potassium deficiencies appear as yellowing on the edges of lower leaves. The yellowing of corn leaves from a lack of potassium in the soil starts near the base of the stalk and continues up the plant as the deficiency continues. If the soil is dry, then the problem can occur even when potassium levels in the soil are sufficient.
This is because soil moisture is needed for the roots to move the potassium through the soil. During times of drought, root growth slows, and potassium deficiencies begin. To prevent this issue, keep water regularly and fertilize only when needed.
Sulfur deficiencies
Sulfur deficiencies appear as yellowing leaves like that of nitrogen deficiencies only the symptoms are more pronounced in the upper leaves of the plant compared to a nitrogen deficiency. Another sign is the interveinal yellowing of younger leaves.
Sulfur deficiencies are more likely to occur during the early growing season because cold, dry soil conditions will inhibit the release of bioavailable sulfur from organic matter. These deficiencies may correct themselves when temperature and moisture levels rise, allowing for the release of these necessary nutrients into the soil.
Magnesium Deficiencies
Magnesium deficiencies initially appear as yellow interveinal stripes in the lowest leaves, but quickly progress to include round dead spots and reddish-purple tips throughout the plant.
Zinc deficiencies
Zinc deficiency symptoms begin with interveinal yellowing leaves, but as it progresses the color bleaches and the discoloration becomes predominantly white.
Rapid Corn Growth Syndrome
Due to the early arriving ideal growing conditions like warm temperatures and adequate rainfall, early root development in early-season corn can occur, which sometimes leads to Rapid Growth Syndrome. When this happens, the corn leaves don’t unfurl properly, leaving them twisted and tightly wrapped during this time of rapid growth.
Once the leaves unwrap, usually within 3 to 7 days, the outer foliage will appear rippled while the inner foliage will be yellow. This issue usually resolves itself as the plant continues to grow and rarely has any impact on crop production. To prevent this problem, try to plant just as the soil temperature reaches 50 degrees Fahrenheit.
Fertilizer Burn
Foliar applications of general liquid fertilizers can cause damage that leads to the yellowing of corn plants. This is due to the sensitive nature of the foliage compared to the strength of the natural or chemical compound being used to add the necessary nutrients for crop production. This is why it is best to focus your fertilization efforts on the soil instead of on the plants themselves. Rinsing your plants after any potential fertilizer contact is recommended to try and limit the effect of the fertilizer burn.
Anhydrous ammonia (NH3) is an ingredient present in many premixed fertilizers. In some cases, this compound releases a vapor that can scorch the foliage leading to the yellowing of its leaves. The corn plant will die if it is severely damaged. Injury from ammonia is more common during dry conditions, so limit its use during the heat of the summer.
Urea-Ammonium Nitrate (UAN) is a common fertilizer that can cause leaf burn when broadcasted on a field of vulnerable young corn plants. The yellowing of the leaves will be focused near to leaf tips and margins. The corn plant will survive if the damage is not severe. Be careful not to increase the application rates when treating larger plants.
Verdict: Corn Plant Leaves Turning Yellow
Yellowing leaves, or chlorosis, is an important first sign that indicates there is a problem such as damage from drought, blights, or pests. All cases of bacteria, fungi, or insect damage should include evidence of actual leaf injury along with the presence of yellowing leaves.
Yellowing leaves can also be a sign of damaged caused by improper herbicide or fertilizer applications, which would typically only appear on the top of the plant that was exposed to the chemical. Of the many reasons that corn plants can have yellowing leaves, the most common causes are inadequate watering, nitrogen and potassium deficiencies, rapid corn growth syndrome, and fertilizer burns.
If caught and rectified quickly, these problems can be easy to fix by adhering to proper watering and fertilizing schedules and techniques.
