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By Wes Chun, Ph.D., Chief Science Officer Emeritus
Introduction
Nitrogen is a key component in bio molecules such as DNA, RNA, enzymes, proteins, and important compounds such as chlorophyll. Since amino acids are the building blocks for these molecules, it is a wise fertilizer choice to supply nitrogen to plants. Since nitrogen contributes three to four percent of a plant’s biomass, a good supply of nitrogen is needed for proper plant growth. However not all nitrogen fertilizers are the same and selection of the right form of nitrogen can go a long way towards efficiently producing a crop.
Nitrogen for plants comes in various forms. Atmospheric nitrogen can be converted to plant-available amino acids by symbiotic rhizobial bacteria or free-living bacteria such as Azotobacter and Cyanobacterium. Conventional agriculture uses synthetic quick release nitrogen fertilizers such as ammonium nitrate and urea. Organic agriculture has a number of options for delivering nitrogen that range from slow to quick release. For example, poultry litter is a slow release fertilizer that requires microbial activity to release plant available amino acids. On the other hand, water-soluble amino acids are immediately available for plant use and are thus considered quick release.
Roots and shoots have passive and active uptake systems for small molecules such as ammonia, nitrates, and amino acids. Small synthetic molecules and amino acids move from higher concentrations outside the plant to lower concentrations inside the plant through natural plant openings. Active transport systems also import these nutrients into the plant and play an important role when concentration gradients from the soil to the plant are low. Active transport mechanisms require energy while passive systems do not. Thus, root and shoot applications of plant available nitrogen can quickly deliver nitrogen into plants. Deficiency symptoms can be ameliorated after foliar applications in as little as three days depending on the plant and the severity of the deficiency. However, many synthetic fertilizers are mineral salt based and care must be taken to avoid injury. Amino acids contain very low amounts of salts so injury will not be an issue.
There are numerous synthetic and organic options to provide nitrogen to plants. Synthetic nitrogen fertilizers used properly are useful tools. However, overapplication or climatic events can cause crop and environmental problems. Fertilizers like amino acid fertilizers offer a low risk, environmentally friendly option for nitrogen fertilization. Complex organic fertilizers such as chicken litter are great for providing nitrogen throughout the growing season. Amino acid fertilizers can be used to ameliorate nitrogen deficiencies or to provide additional nitrogen for nitrogen hungry plants such as lettuce.
Summary
Thus, amino acids have two major attributes that make them a valuable tool for nitrogen fertilization of crops. First, they are readily absorbed by plants through the foliage and roots and are low salt. Thus, they can be used as a foliar spray with no risk of burning. Additionally, amino acids are used directly by the plant to make enzymes and proteins thus saving quite a bit of plant energy. The plant has to expend energy to convert nitrates into ammonia to manufacture amino acids. The energy saved can thus be used for other plant metabolic processes such as growth, reproduction, and responding to biological and environmental stresses.
