Growing Medium pH Influences Nutrient Availability
Yellowing tissue, distortion of growth or leaf necrosis: Have you thought about monitoring the pH of your growing substrate? Micronutrient deficiencies are not desirable. Learn how to recognize and avoid them.
"Iron-Manganese deficiency in geranium"
During the crop cycle, some growers may have experienced pH drift that can affect the quality of their plants. The pH of the growing medium does not directly harm the plant; however, it influences the availability of nutrients that the plant can acquire from the growing medium.
Macronutrient Availability
Macronutrients; nitrogen, phosphorus, potassium, calcium, magnesium and sulfate; are needed by all plants in large quantities. The pH of the growing medium has some influence on their availability, especially phosphorus and magnesium, but they are needed in large quantities. Even with an improper growing medium pH, the amount of macronutrients that are tied up or made available is little compared to how much is required by the plant. Often the influence of pH on macronutrients goes unnoticed.
Micronutrient Availability
Micronutrients, on the other hand, are needed in much lower quantities. If the pH of the growing medium is too high or too low, it will significantly influence micronutrient availability for plants. If the growing medium pH rises above 6.0, iron, manganese, zinc, copper and boron start to become insoluble and unavailable for plant uptake. If the pH drops below 5.5, these elements become soluble and are available to the plant. Molybdenum, on the other hand, is the opposite. It becomes soluble at high pH and insoluble at low pH.
Low Availability of Micronutrients
Iron deficiency is the most common micronutrient deficiency and commonly occurs in bacopa, calibrachoa, dianthus, diascia, nemesia, pansy, petunia, scaevola, snapdragon, verbena and vinca. The classic symptom is interveinal chlorosis (yellow leaves with green veins) of the new leaves. Manganese deficiency has similar visual symptoms and can also be seen in these crops. Pansy, petunia and salvia are sensitive to boron deficiency which is expressed as die back of the growing tips and thickened, brittle and distorted side branches. Zinc, copper or molybdenum deficiencies are uncommon, but also cause chlorosis, distortion or curling of new growth. Plants should be tested to confirm micronutrient deficiencies.
There are also non-pH related causes for micronutrient deficiencies. First, if fertilizer application rates are low, then micronutrients are provided at insufficient levels. Second, during cloudy, cool weather, plants use little water. Since fertilizer is dissolved in the growing medium solution, insufficient micronutrients are taken up and nutrient deficiencies occur. Third, if plant roots are diseased they cannot effectively take up micronutrients, leading to deficiencies.
High Availability of Micronutrients
The most common micronutrient toxicity is iron-manganese toxicity and it is occurs when the growing medium pH is too low. It is expressed on the lower leaves of geraniums, lisianthus, marigolds, New Guinea impatiens and pentas as bronze/brown speckles and necrotic leaf edges. Boron toxicity can occur in mums, poinsettia and zinnia especially if high levels are found in the water. Symptoms are similar to iron-manganese toxicity. Zinc, copper or molybdenum toxicities are uncommon, but test the media and tissue for confirmation.
Excessive availability of micronutrients can also result from over application of water soluble fertilizer or excessive release of controlled release fertilizer. Check water sources as they can provide excessive micronutrients, especially boron. Regardless of a deficiency or toxicity, always test the growing medium and plant tissue to confirm the problem.
For help managing growing media pH and nutrition for your crops grown in PRO-MIX®, please feel free to contact your growers services rep:
Lance Lawson in the Mountain West and JoAnn Peery in the Midwest.
Macronutrient Availability
Macronutrients; nitrogen, phosphorus, potassium, calcium, magnesium and sulfate; are needed by all plants in large quantities. The pH of the growing medium has some influence on their availability, especially phosphorus and magnesium, but they are needed in large quantities. Even with an improper growing medium pH, the amount of macronutrients that are tied up or made available is little compared to how much is required by the plant. Often the influence of pH on macronutrients goes unnoticed.
Micronutrient Availability
Micronutrients, on the other hand, are needed in much lower quantities. If the pH of the growing medium is too high or too low, it will significantly influence micronutrient availability for plants. If the growing medium pH rises above 6.0, iron, manganese, zinc, copper and boron start to become insoluble and unavailable for plant uptake. If the pH drops below 5.5, these elements become soluble and are available to the plant. Molybdenum, on the other hand, is the opposite. It becomes soluble at high pH and insoluble at low pH.
Low Availability of Micronutrients
Iron deficiency is the most common micronutrient deficiency and commonly occurs in bacopa, calibrachoa, dianthus, diascia, nemesia, pansy, petunia, scaevola, snapdragon, verbena and vinca. The classic symptom is interveinal chlorosis (yellow leaves with green veins) of the new leaves. Manganese deficiency has similar visual symptoms and can also be seen in these crops. Pansy, petunia and salvia are sensitive to boron deficiency which is expressed as die back of the growing tips and thickened, brittle and distorted side branches. Zinc, copper or molybdenum deficiencies are uncommon, but also cause chlorosis, distortion or curling of new growth. Plants should be tested to confirm micronutrient deficiencies.
There are also non-pH related causes for micronutrient deficiencies. First, if fertilizer application rates are low, then micronutrients are provided at insufficient levels. Second, during cloudy, cool weather, plants use little water. Since fertilizer is dissolved in the growing medium solution, insufficient micronutrients are taken up and nutrient deficiencies occur. Third, if plant roots are diseased they cannot effectively take up micronutrients, leading to deficiencies.
High Availability of Micronutrients
The most common micronutrient toxicity is iron-manganese toxicity and it is occurs when the growing medium pH is too low. It is expressed on the lower leaves of geraniums, lisianthus, marigolds, New Guinea impatiens and pentas as bronze/brown speckles and necrotic leaf edges. Boron toxicity can occur in mums, poinsettia and zinnia especially if high levels are found in the water. Symptoms are similar to iron-manganese toxicity. Zinc, copper or molybdenum toxicities are uncommon, but test the media and tissue for confirmation.
Excessive availability of micronutrients can also result from over application of water soluble fertilizer or excessive release of controlled release fertilizer. Check water sources as they can provide excessive micronutrients, especially boron. Regardless of a deficiency or toxicity, always test the growing medium and plant tissue to confirm the problem.
For help managing growing media pH and nutrition for your crops grown in PRO-MIX®, please feel free to contact your growers services rep:
Lance Lawson in the Mountain West and JoAnn Peery in the Midwest.
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Horticulture Specialist Troy Buechel explains everything you need to know about PRO-MIX HP BIOFUNGICIDE + MYCORRHIZAE, a high porosity, specialized substrate with active ingredients to provide a great growing environment to your plants.
MYKE® ONLINE TRAINING
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Use the link below to access the 5 short videos. The trainings are easy, informative, and very helpful!
All crops have specific light requirements. By knowing minimum and optimum levels of light for our crop we can manage our environment to improve crop performance. When the ambient light exposure is below the minimum requirements we need to apply supplemental lighting in order to maintain our crop production at a healthy and consistent pace.
On the other hand when our ambient light levels are optimal we can regulate light to influence other aspects of our environment such as air temperature and humidity by applying specific products to reduce heat exposure in our greenhouse.
Light management will always be a key factor in our crop performance. As our series continues we will discuss specific products to manage light and heat within your greenhouse. Let’s take a look at some crop specific light requirements and how they affect our crop performance. DLI or Daily Light Integral refers to the number photons received by a plant that provide photosynthetic activation.
Lettuce and Herbs – Minimum 12 DLI, Optimum 17 DLILettuce and herbs are crops that can be grown in both greenhouse and indoor vertical farming. Maintaining DLI below 17 for an indoor vertical farming system is recommended in order to mitigate environmental conditions which can affect calcium uptake and cause tip burn in your crop.
Lettuce and some herbs are extremely sensitive to high temperatures. Therefore, proper DLI management inside a greenhouse reduces the chances of accumulating excess heat that could promote bolting of your crop and the proliferation of both mildew and pest. Thus, because of its influence on temperature, light management is very important to maintain optimum environmental conditions to achieve the product quality required for the market.
Tomatoes (Minimum 20 DLI), Cucumbers (Minimum 15 DLI) and Peppers (Minimum 20 DLI) – Optimum 30 DLITomatoes, cucumbers and peppers are crops with higher DLI requirements than their leafy green cousins. They also enjoy a higher temperature. One major challenge when growing tomatoes, peppers, cucumbers vertically inside a greenhouse is how to achieve a uniform distribution of DLI for stable consistent fruit generation. Tall crops tend to shade each other, creating an environment where optimal DLI levels are only achieved in the upper canopy. To counteract this effect when relying heavily on ambient light diffusion creating products, such as shade paints, must be employed to scatter the light in different directions to reach every level of the canopy.
Properly designed supplemental lighting can also be employed to reach all levels of the plant canopy and maintain balanced DLI levels when ambient light is insufficient. Too much direct light can cause stress in young leaves and also can cause sunburn issues in fruit. Remember to always use the right products to maintain proper DLI levels and control how light is entering your greenhouse.
Hemp – Minimum 20 DLI, Optimum 30 DLIHemp is a crop that loves light, and can be grown under conditions similar to tomatoes, cucumbers and peppers. However, when cultivating hemp, maintaining the proper photoperiod is just as important to production as optimizing DLI. Previous research demonstrated short days promote flowering in this crop, and has also concluded that environmental factors such as temperature and photoperiod, can greatly influence the reproductive cycles of Hemp.
There are three distinct phases in Hemp cultivation: propagation, vegetative and flowering. Recent research regarding light application for high yield production purposes recommend the use of long photoperiods (18 hours) for the propagation and vegetative phases and short photoperiods (12 hours) for the flowering phase when using artificial lighting.
Strawberry – Minimum 17 DLI, Optimum 20 DLIStrawberries enjoy a much lower light requirement than vine crops. Due to plant anatomy diffuse lighting is also recommended to enhance photosynthetic activity in strawberries and avoid leaf shading within the plant. Strawberry cultivars have a strong response to both photoperiod and temperature. We can find short-day, long-day and day-neutral cultivars in strawberries.
Previous research demonstrated that the most common type of cultivar on the market, day-neutral, can also exhibit an accelerated flowering response under long-day conditions. Therefore, by the use of supplemental lighting, it is possible to promote more abundant flowering earlier in strawberries and have your crop ready for the market in less time. Lower temperatures during non-photosynthetic activation periods have been shown to improve flavor.
Microgreens – Minimum 10 DLI, Optimum 12 DLIMicrogreens are young plants with low light requirements grown in vertical farming systems using artificial lighting and harvested before ever reaching maturity. Because these crops have such a fast rate of growth it is important to monitor and maintain proper DLI levels to avoid over-stretching due to low light or burning due to excess light. Usually light-burn can be triggered when plants are too close to lamps.
An important aspect to get perfect size, texture and color microgreens is to work with good light quality. Most often the correct balance of red and blue lighting can achieve great quality in microgreens.
Click the button below to learn more about our L1000 Grow Light System.
