Posted By: Marlowe DeVille /
Increasing Nitrogen Efficiency with Foliar-Applied Amino Acid Fertilizer
Nitrogen is critical for plant growth, development, and reproduction – plants literally can’t live without it. For example, many of the small structures inside plant cells, like DNA and the amino acids that make up enzymes and other proteins, are made of molecules containing nitrogen. Altogether, about three to four percent of a plant’s above ground biomass is nitrogen – it is a fundamental building block of both structure and function in plants.
Fertilizers are needed, in general, because natural soils cannot always provide the amount of nutrients that would be required for optimal plant growth. Even though 78 percent of our atmosphere is nitrogen gas, this nitrogen is not directly accessible to plants through the air: plants can only absorb nitrogen in certain forms. Under natural conditions, soils contain limited amounts of these forms of useable nitrogen, and so plants cannot reach their full potential without the application of supplemental nitrogen fertilizer.
The Traditional Approach: Urea Soil Application
In general, we think of plants absorbing nutrients through their roots – and in many cases, that’s exactly what happens with nitrogen. But only certain forms of nitrogen can be absorbed through plant roots, and many common nitrogen fertilizers (including urea) must undergo transformations in the soil nitrogen cycle before plants can use them. This cycle, which includes soil bacteria processes known as ammonification and nitrification, happens over days or weeks, with the key product for plants being nitrate and other ions that are easily absorbed through tiny channels in the roots.
As a result of the time needed for multiple process steps before the urea fertilizer can be absorbed by plants as nitrate, much of the originally-applied nitrogen can be lost to the atmosphere (volatilization) or carried away by water (leaching). In addition, the initial step of ammonification creates ammonia gas, which is toxic to many seeds and seedlings, before the nitrification process changes it, eventually, into nitrate.
When the nitrate finally makes its way into the roots of the plant, it must be carried from there to an area of active growth (usually up towards the leaves), where the plant combines it with other ions or small molecules to create larger amino acid chains and peptids which are building blocks needed to generate plant growth.
The Green Future: Amino Acid Foliar Application
In contrast to urea nitrogen, which can be applied either foliar or to the soil, and needs to be converted before it's transported up the plant, and then incorporated into larger molecules, amino acid nitrogen is already in the ‘larger molecule’ form, and so plants can put it to work directly and much more efficiently. Amino acids are available to the plant immediately on application, so there’s no need for the bacterial processes prior to absorption, far fewer losses through leaching and volatilization, and no production of toxic ammonia. When fertilized with amino acids, plants no longer need to build large molecules from small ones and can save significant amounts of energy that would have been used for nutrient uptake and amino acid synthesis. By expending less energy transporting nutrients and combining them into useful molecules, the plant in turn has more energy for larger yields, pest and disease resistance, and higher quality production, thus reducing plant stress.
“These and other developments in the field of agriculture contain the makings of a new revolution. It is not a violent Red Revolution like that of the Soviets, nor is it a White Revolution like that of the Shah of Iran. I call it the Green Revolution."
William Gaud. 1968. Former Director of the US Agency for International Development
Amino acids are the most efficient form of nitrogen fertilizer to use on plants. High-quality, organic, amino acid fertilizers are relatively new to the market and generally 12-15 percent nitrogen (compared to 45 percent for urea). They are water soluble and able to act as chelators for ions, have a pleasant odor and practically no salt, and will never cause burns when applied at labeled use rates.
The optimal use of amino acid nitrogen is a foliar application that delivers the amino acids directly to the leaves and stems, where they can be absorbed through pores called stomata. This does not preclude soil applications of amino acid based fertilizers mycorrhizal and non-mycorrhizal plants can acquire organic nitrogen as amino acids and peptides via, root uptake. While nitrate ions are small enough to be absorbed through tiny channels in the roots of a plant, amino acid chains are too large for this pathway and are more quickly and easily absorbed into the leaves through stomata.
Since they are already located in the growing portion of the plant (i.e. leaves), the amino acid chains can be immediately used as building blocks for growth without the need for further transport or breakdown.
Studies have shown that foliar feeding can provide 95 percent efficiency of use, compared to only ten percent efficiency of use from soil fertility applications: small amounts of foliar-applied nutrients can replace larger quantities of soil-applied fertilizer, reducing total input costs. In addition, the speed of absorption from foliar applications has been shown to be much faster than adsorption from soil applications.
Why amino acids? More efficient!
Plants with access to amino acid chains and peptides don’t need to expend the energy to build the amino acid chains themselves, allowing more energy to be allocated for larger yields, pest and disease resistance, and higher quality production.
Foliar feeding can be up to 20 times more efficient then soil applications; foliar nutrient use efficiency can reach 95 percent.
The Amino Acid Advantage
Amino acids are a form of nitrogen that is readily available to the plant. Other organic fertilizers that require mineralization are less effective as foliar sprays since microorganism populations are lower on the foliage than they are in the soil.