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When discussing foliar absorbed nutrients several concepts need to be clarified. The first concept one needs to understand is that the "non-root" parts of plants can and will take up nutrients from nutrient sprays and other applications. This concept has been shown over a long period of time by many researchers.
Foliar absorption of mineral nutrients by above ground plant parts including leaves stems and flowers have been reported for over 200 years. Interest however has been mainly since the 1950's. this interest has grown over the years because of the increased costs of fertilizers, environmental concerns about leaching and runoff, a better understanding of how to facilitate the absorption process and a better understanding of plant growth. Minor element deficiencies in fruit have been corrected by foliar applications for 80 to 90 years. More recently over the last 40 years or so, foliar absorption of the macronutrients has also been studied extensively. It is now known that not only nutrients can be absorbed but also pesticides, growth regulators, organic acids and many carbohydrates.
Among the advantages to foliar absorbed nutrients include the fact that they can be rapid and effective, with quick plant response. Because they are so effective they require less fertilizer input by avoiding soil fixation, leaching and runoff. They are applied to the leaf blade and allowed to remain there until fully absorbed. You do not water in. Today we have the knowledge of how plants grow in order to make the most effective use of this technique. Other advantages revolve around the fact that they are effective when the turf has a restricted root system from such things as being closely mowed, periods of environmental stress, seasonal root loss, periods of low photosynthetic output and correspondingly low carbohydrate reserve.
Some nutrients become fixed in the soil and results in low efficiency as a root absorbed nutrients. Foliar applications of nutrients as a supplementary fertilizer are highly effective.
Factors affecting foliar absorption.
Several factors will affect foliar absorption include relative humidity, temperature, pH of the nutrient solution, variety of the turf, age of the leaf, concentration of the nutrient solution, difference in the nutrient compounds(formulations) us of surfactants and the addition of non-nutrient facilitating or carrier-mediated agents.
Humidity and temperature have a direct relationship with absorption of nutrients and as they increase, penetration also increases. The total amount of time the nutrient is in contact with the leaf is critical. Optimum pH is a factor that varies from nutrient to nutrient and most good formulators recognize the need to have optimum pH for the nutrient used.
Many chemical compounds are ineffective as foliar nutrients. For example Shafer and Reed studied a total of 31 organic and inorganic potassium compounds for their efficacay as a foliar fertilizer. Their results showed a broad spectrum in foliar absorption of potassium from both organic and inorganic carriers. Studies from other researchers on many other nutrient compounds show similar results.
Modern Foliars
The effectiveness of modern foliar fertilizers varies significantly and is directly proportional to the quality of the product. Using both organic and inorganic facilitating agents to transport the cations into and throughout the plants has become a very exact science and is the main difference in the claims between companies in the foliar business. Golf course superintendents need to separate facts from claims and get a high degree of confidence in the company they choose to work and to purchase from. The process of building excellent foliar fertilizers is an exacting and complex one.
Many humic and organic materials have the capacity to bind substantial amounts of metals and other cations, and they can therefore exert considerable control over the supply and availability of nutrient elements to plants and in water.
When the metal ion combines with an electron donor, the resulting substance is said to be a complex or coordination compound. If the donor atoms are attached not only to the metal ion but also to each other as well forming a ring, it creates a chelate.
There are good complexes and bad complexes and there are good and bad chelates. Some of the organic agents used in these products are: humic acids from many sources, fulvic acids, ligno sulfates, amino acids, sugars and carbohydrates, hydrolyzed protein mixes and derivatives from the wood pulp industry. Many of these have low stability constants and when mixed with anions such as phosphates may result in precipitation. Once again select your products wisely. Organics are biodegradeable and available to the plant and the soil micro community as an energy source.
Since the 1950's synthetic chelating agents have been used as aids in plant nutrition. Among the more popular ones are EDTA, HEDTA and EGTA, and others. They are cost effective and can be effective if used properly but they are generally not biodegradable. Synthetic chelating agents are intended to be used in the soil to prevent the attached nutrients from forming a bond with the soil colloids and remain more available for root uptake. In general however they do not work well as foliar fertilizer agent.
Synthetic chelates are used extensively in many agriculture and turf products. Some researchers have reported that they may remain as a residue in the plant tissue or in the soil tying up other nutrients and they provide no additional energy source.
Mobility
Absorption is only one aspect of a foliar fertilizer. In addition, the absorbed nutrient generally must be translocated throughout the plant. While absorption is a key process in selecting a foliar applied nutrient, the extent of redistribution or mobility of each nutrient in the plant is an important consideration also.
Buyer Beware
There is little regulation over the complexing and chelate foliar industry:
In his thesis for his PH. D. degree from Michigan State University in 1956 H.B. Tukey Jr. researched Nutritional Foliar Sprays. He made this observation:
"Foliar fertilizers produce quick, visible results and can increase the effectiveness of fertilizer applications to the soil, reducing total amounts of fertilizer applied."
He showed that it works like this:
In photosynthesis; sunlight, carbon dioxide from the atmosphere, water and nutrients, along with chlorophyll in the leaf, combine to produce carbohydrates for plant growth and health. The nutrients in the soil are soluble in the ground water and enter the plant with the water through the membrane of the roots and are carried up the xylem tissue and distributed throughout the leaf where the carbohydrates are produced. The carbohydrates are then distributed throughout the plant and carried by the phloem to the root for storage.
When we apply foliar fertilizer containig the proper nutrients for photosynthesis directly to the leaf, the plant begins to produce more carbohydrates and in the process requires more water. The stomata on the leaf open allowing water vapor to escape, which reduces the water pressure in the xylem tissue allowing more water to flow up the vascular bundle. In turn more water is absorbed into the roots to replace the water moving up. If good nutrition is available in the soil surrounding the root, extra nutrients enter the plan with the water.
If you visualize the plant as a water pump, the foliar fertilizer acts as a primer, priming the pump and bringing more nutrition into the plant.
It is important to remember that the foliar fertilizer actually increases the total uptake of nutrients by several folds over the small amount of foliar fertilizer applied.
The application Foliar Fertilizers do not replace the soil applied fertilizer, but increases their uptake.
Foliar absorption of mineral nutrients by above ground plant parts including leaves stems and flowers have been reported for over 200 years. Interest however has been mainly since the 1950's. this interest has grown over the years because of the increased costs of fertilizers, environmental concerns about leaching and runoff, a better understanding of how to facilitate the absorption process and a better understanding of plant growth. Minor element deficiencies in fruit have been corrected by foliar applications for 80 to 90 years. More recently over the last 40 years or so, foliar absorption of the macronutrients has also been studied extensively. It is now known that not only nutrients can be absorbed but also pesticides, growth regulators, organic acids and many carbohydrates.
Among the advantages to foliar absorbed nutrients include the fact that they can be rapid and effective, with quick plant response. Because they are so effective they require less fertilizer input by avoiding soil fixation, leaching and runoff. They are applied to the leaf blade and allowed to remain there until fully absorbed. You do not water in. Today we have the knowledge of how plants grow in order to make the most effective use of this technique. Other advantages revolve around the fact that they are effective when the turf has a restricted root system from such things as being closely mowed, periods of environmental stress, seasonal root loss, periods of low photosynthetic output and correspondingly low carbohydrate reserve.
Some nutrients become fixed in the soil and results in low efficiency as a root absorbed nutrients. Foliar applications of nutrients as a supplementary fertilizer are highly effective.
Factors affecting foliar absorption.
Several factors will affect foliar absorption include relative humidity, temperature, pH of the nutrient solution, variety of the turf, age of the leaf, concentration of the nutrient solution, difference in the nutrient compounds(formulations) us of surfactants and the addition of non-nutrient facilitating or carrier-mediated agents.
Humidity and temperature have a direct relationship with absorption of nutrients and as they increase, penetration also increases. The total amount of time the nutrient is in contact with the leaf is critical. Optimum pH is a factor that varies from nutrient to nutrient and most good formulators recognize the need to have optimum pH for the nutrient used.
Many chemical compounds are ineffective as foliar nutrients. For example Shafer and Reed studied a total of 31 organic and inorganic potassium compounds for their efficacay as a foliar fertilizer. Their results showed a broad spectrum in foliar absorption of potassium from both organic and inorganic carriers. Studies from other researchers on many other nutrient compounds show similar results.
Modern Foliars
The effectiveness of modern foliar fertilizers varies significantly and is directly proportional to the quality of the product. Using both organic and inorganic facilitating agents to transport the cations into and throughout the plants has become a very exact science and is the main difference in the claims between companies in the foliar business. Golf course superintendents need to separate facts from claims and get a high degree of confidence in the company they choose to work and to purchase from. The process of building excellent foliar fertilizers is an exacting and complex one.
Many humic and organic materials have the capacity to bind substantial amounts of metals and other cations, and they can therefore exert considerable control over the supply and availability of nutrient elements to plants and in water.
When the metal ion combines with an electron donor, the resulting substance is said to be a complex or coordination compound. If the donor atoms are attached not only to the metal ion but also to each other as well forming a ring, it creates a chelate.
There are good complexes and bad complexes and there are good and bad chelates. Some of the organic agents used in these products are: humic acids from many sources, fulvic acids, ligno sulfates, amino acids, sugars and carbohydrates, hydrolyzed protein mixes and derivatives from the wood pulp industry. Many of these have low stability constants and when mixed with anions such as phosphates may result in precipitation. Once again select your products wisely. Organics are biodegradeable and available to the plant and the soil micro community as an energy source.
Since the 1950's synthetic chelating agents have been used as aids in plant nutrition. Among the more popular ones are EDTA, HEDTA and EGTA, and others. They are cost effective and can be effective if used properly but they are generally not biodegradable. Synthetic chelating agents are intended to be used in the soil to prevent the attached nutrients from forming a bond with the soil colloids and remain more available for root uptake. In general however they do not work well as foliar fertilizer agent.
Synthetic chelates are used extensively in many agriculture and turf products. Some researchers have reported that they may remain as a residue in the plant tissue or in the soil tying up other nutrients and they provide no additional energy source.
Mobility
Absorption is only one aspect of a foliar fertilizer. In addition, the absorbed nutrient generally must be translocated throughout the plant. While absorption is a key process in selecting a foliar applied nutrient, the extent of redistribution or mobility of each nutrient in the plant is an important consideration also.
Buyer Beware
There is little regulation over the complexing and chelate foliar industry:
- The presence of an organic or synthetic chelating agent in the formulation legally makes the product a chelate regardless of how much is in the mix.
- It does not matter whether there is enough chelating agent in the mixture to chelate all the metals in the formulation or not to be considered a chelate.
- Any agent that can be shown to cause chelation is considered a chelate, without regard to whether it is stable or not.
- Unstable chelates that precipitate when mixed with anions, such as phosphorous, are poorly absorbed by the plants and do not translocate well in the plant.
- The concentration of these complexing and chelating agents in the various formulations need not be on the label.
In his thesis for his PH. D. degree from Michigan State University in 1956 H.B. Tukey Jr. researched Nutritional Foliar Sprays. He made this observation:
"Foliar fertilizers produce quick, visible results and can increase the effectiveness of fertilizer applications to the soil, reducing total amounts of fertilizer applied."
He showed that it works like this:
In photosynthesis; sunlight, carbon dioxide from the atmosphere, water and nutrients, along with chlorophyll in the leaf, combine to produce carbohydrates for plant growth and health. The nutrients in the soil are soluble in the ground water and enter the plant with the water through the membrane of the roots and are carried up the xylem tissue and distributed throughout the leaf where the carbohydrates are produced. The carbohydrates are then distributed throughout the plant and carried by the phloem to the root for storage.
When we apply foliar fertilizer containig the proper nutrients for photosynthesis directly to the leaf, the plant begins to produce more carbohydrates and in the process requires more water. The stomata on the leaf open allowing water vapor to escape, which reduces the water pressure in the xylem tissue allowing more water to flow up the vascular bundle. In turn more water is absorbed into the roots to replace the water moving up. If good nutrition is available in the soil surrounding the root, extra nutrients enter the plan with the water.
If you visualize the plant as a water pump, the foliar fertilizer acts as a primer, priming the pump and bringing more nutrition into the plant.
It is important to remember that the foliar fertilizer actually increases the total uptake of nutrients by several folds over the small amount of foliar fertilizer applied.
The application Foliar Fertilizers do not replace the soil applied fertilizer, but increases their uptake.
