"Asclepius" C#6

*Nitrogen (N) (MOBILE)* Macronutrient Nitrogen is an essential nutrient because it is a part of the makeup of all plant and animal proteins. The nutritive value of the food we eat is largely dependent on having an adequate supply of N. Nitrogen is required in greater quantities by crops than any of the other essential nutrients, except potassium (K). Some crops take up more K than N. Table 1 shows how much N is required by a number of common crops. Inorganic nitrate and ammonium are the major forms of N taken up by plant roots. Although the amount of N stored in soil organic matter is large (often more than 1,000 lbs/A), the amount released and available for plant uptake is relatively small. Often, that release is not synchronized with plant demand. Very little N is found in rocks and minerals. Organic matter releases N slowly, the rate being controlled by soil microbial activity (influenced by temperature, moisture, pH, and texture). In general, about 20 to 30 lb N/A are released annually for each 1 percent organic matter contained in the upper 6 to 7 inches of soil. One of the products of organic decomposition (mineralization) is ammonium, which can be held by the soil, taken up by crop plants or converted to nitrate. The nitrate is used by plants, leached out of the root zone, or converted to gaseous N and lost back into the atmosphere. The conceptual relationship between plant-unavailable N (organic matter) and plant-available N (ammonium and nitrate) and soil temperature effects are illustrated in Figures 1 and 2. *Phosphorus (P) (MOBILE)* Macronutrient Phosphorus is present in every living cell, both plant, and animal. No other nutrient can be substituted for it when it is lacking. Phosphorus is one of the 17 essential nutrients that plants need for growth and reproduction. Phosphorus is considered one of the three major nutrients along with nitrogen (N) and potassium (K). They are termed major nutrients because of the relatively large amounts utilized by plants (table 1) and the frequency with which their deficiencies limit plant growth. Phosphorus is a vital component in the process of plants converting the sun’s energy into food, fiber, and oil. Phosphorus plays a key role in photosynthesis, the metabolism of sugars, energy storage and transfer, cell division, cell enlargement, and the transfer of genetic information. Phosphorus promotes healthy root growth, promotes early shoot growth, speeds ground cover for erosion protection, enhances the quality of fruit, vegetable, and grain crops, and is vital to seed formation. Adequate P increases plant water use efficiency, improves the efficiency of other nutrients such as N, contributes to disease resistance in some plants, helps plants cope with cold temperatures and moisture stress, hastens plant maturity, and protects the environment through better plant growth. Plant roots can only acquire P from the soil when it is dissolved in soil water. Since only very low concentrations of P are present in the soil water, P must be continually replenished from soil minerals and organic matter to replace the P taken up by plants. Plant roots generally absorb P as inorganic orthophosphate ions. *Potassium (K) (MOBILE)* Macronutrient Potassium is an essential plant macronutrient taken up in large quantities, like nitrogen. In plants, K does not become part of complex organic molecules. It moves as a free ion and performs many functions. Potassium in Plants In plants, K is involved in many essential functions. It serves to: • regulate water pressure in plant cells, affecting cell extension, gas exchange, and movement of leaves in response to light; • activate enzymes that help chemical reactions take place; • synthesize proteins; • adjust pH within plant cells; • increase carbon dioxide fixation during photosynthesis; • transport chemical compounds; and • balance electrical charges in various parts of cells. Harvesting crops remove K from the soil. The quantity removed varies with the quantity of biomass and K content of the plant organs harvested (table 1). table 1. Potassium uptake and removal rates for selected crops. Plants that are supplied with adequate K are better able to withstand stress, insect damage, and many plant diseases compared with plants low in K. As plants age, rainfall leaches K from plant leaves, depositing K at the soil surface. Plants, therefore, redistribute K from lower depths to the soil surface, a process termed “uplift.” Uplift contributes to nutrient stratification in no-till and reduced tillage systems and affects how soil tests change in response to K additions and crop removal. Plants can only access K when it is dissolved in the soil solution. Contributors to potentially plant-available K are: • K redistributed from other areas, including irrigation water, precipitation, commercial fertilizer, manure, biosolids, and sediment deposition; • weathering of K-containing primary minerals like micas and some feldspars; • K released from the interlayers of the layer silicate minerals illite, vermiculite, and smectite; and • K desorption from surfaces and edges of layer silicate minerals, termed “exchangeable K.” Exchangeable K is measured by soil tests and is considered readily available for plants. Layer silicate minerals that release Selenium K can also “fix” K, or bond K in interlayer positions, thereby removing it from the soil solution. Fixation and release of K by these minerals is dynamic throughout the year. *Boron (B) (IMMOBILE)* Micronutrient Over the past 80 years, hundreds of reports have documented the role of boron (B) in agricultural crops around the world. Responses to fertilization have been documented in almost every state and province in the U.S. and Canada. Alfalfa frequently responds, and so do a large number of fruit, vegetable, and field crops. *Calcium (C) (IMMOBILE)* Macronutrient Calcium is classified as a “secondary nutrient” that is needed in relatively large amounts by plants in the form of Ca 2+. In some species, the requirement for Ca is greater than for the macronutrient phosphorus (P). The critical Ca concentration in plants varies widely, ranging from about 0.2% in grasses, 1.0 to 1.25% in fruit crop foliage, to 2.0% in cotton leaves 1. The amount of Ca taken up by various crops is listed in table 1. Calcium plays a key role in the cell wall structure and membrane integrity. In addition to plant stability, strong cell walls help prevent invasion by numerous fungi and bacteria. Calcium also promotes proper plant cell elongation, participates in enzymatic and hormonal processes, and plays a role in the uptake processes of other nutrients. calcium in Soils The total amount of Ca in soils normally ranges from 0.7 to 1.5% in noncalcareous, temperate soils. Highly weathered tropical soils typically have a lower Ca content, ranging from 0.1 to 0.3%, while calcareous soils may contain as much as 25% Ca. Although there may be tens of thousands of pounds of total Ca/A in the root zone, it is common to have less than 100 lb of Ca actually soluble at any one time. The solubility of Ca depends on several soil factors, including: • Soil pH – soils with higher pH typically contain more available Ca on cation exchange sites • Cation exchange capacity (CEC) – available Ca is affected by both the soil cation exchange capacity and the Ca saturation on the soil cation exchange sites • Presence of other soil cations – Ca is preferentially adsorbed on cation exchange sites. Its solubility and plant availability is influenced by other cations in the soil. Calcium has an important influence on soil properties, especially as it prevents the dispersion of clay. An abundant supply of Ca can help reduce soil crusting and compaction, leading to improved water percolation, and reduced runoff. Calcium is not typically formulated into fertilizer sources specifically to meet plant Ca requirements, but rather as a component of other materials. The most common Ca sources are liming materials, mainly CaCO3. Most acidic soils that have been limed to the proper pH will not have Ca nutritional problems. Calcium is often supplied as gypsum as an amendment to improve soil chemical or physical properties. Clays can disperse in soils with high sodium (Na) content, resulting in poor soil structure and reduced water permeability. Added Ca replaces the Na + on the cation exchange sites and corrects clay dispersion problems. Calcium is a component of several common Nitrogen (N) and P fertilizer materials. *Chloride (Cl) (IMMOBILE)* Micronutrient Chloride is commonly found in nature—from seas, to soils, to the air—it’s everywhere. It is a monovalent anion, having a single negative charge (Cl-). Plants take up the element chlorine in this anionic form. Under standard conditions chlorine (Cl) is an unstable, yellow-green gas. Unlike Cl- , free Cl rarely occurs in nature. Chloride was first generally recognized as a plant nutrient in the mid-1950s. However, its value as a fertilizer supplement was not appreciated until the 1970s when work in the northwestern U.S. and elsewhere showed that some crops may indeed respond to Cl- fertilizer application. Since that time there has been a great deal of work investigating crop response to the addition of Cl-, and determining optimal management practices for Cl- fertilization. Chloride fulfills many important functions in plants. Some of the roles of Cl- in plants are: • Photosynthesis and enzyme activation. Some of the enzymes activated are involved in starch utilization which affects germination and energy transfer. • Transport of other nutrients. Chloride aids in the transport of nutrients such as potassium (K +), calcium (Ca2+), and magnesium (Mg2+) since it acts as a counterion to maintain electrical balance. • Water movement in cells. Cellular Cl- helps water move into cells and also aids in water retention in cells, thereby impacting cell hydration and turgor. • Stomatal activity. Both K and Cl- are involved in the movement of guard cells that control the opening and closing of leaf pores or stomata. • Accelerated plant development. Adequate Cl- in small grain production results in earlier head formation and emergence than where Cl- is deficient. In winter wheat production maturity advances of 5 to 7 days have been observed. • Reduced lodging. Chloride strengthens stems, helping to reduce lodging later in the season. Among the most notable impacts of Cl- is its role in reducing the effects of numerous plant diseases. This effect may be related to its function in osmotic regulation. In wheat, Cl- has been shown to suppress take-all root rot, tan spot, stripe rust, leaf rust, and Septoria, while in corn and grain sorghum it has been shown to suppress stalk rot. Nearly all Cl - in soils exists in soil solution. Chloride, like nitrate (NO3-), is mobile in soils and moves freely with soil water. Thus, under certain conditions it can be readily leached from the root zone. There are several potential sources of Cl- in crop production systems, including rainfall, marine aerosols, volcanic emissions, irrigation water, and fertilizer. Some irrigation water contains substantial amounts of Cl - often enough to meet or exceed crop needs. Atmospheric deposition can be particularly high in coastal areas. But regions further inland, such as the Great Plains of the U.S., have much lower atmospheric deposition of Cl - making the likelihood of response to Cl- fertilizer higher. Where there is a history of Cl containing fertilizer application (such as muriate of potash; also known as MOP, potassium chloride or KCl) it is not likely that Cl- will be limiting for crops. *Cobalt (IMMOBILE)* Micronutrient Cobalt (Co) fertilization is occasionally reported to benefit crop growth, but the need for supplemental Co is rather rare. Cobalt has only recently been recognized as a potentially essential nutrient for plants. Cobalt is necessary for nitrogen (N) fixation occurring within the nodules of legume plants. *Copper (Cu) (IMMOBILE)* Micronutrient Copper is one of eight essential plant micronutrients. When Cu is deficient, common crop responses to its application include reduced disease, increased crop growth and improved quality. Commonly applied Cu sources include fertilizer, animal manures, biosolids, and pesticides. *Iron (Fe) (IMMOBILE)* Micronutrient Iron is a component of many vital plant enzymes and is required for a wide range of biological functions. Most soils contain abundant Fe, but in forms that are low in solubility and sometimes not readily available for plant uptake. *Magnesium (Mg) (MOBILE)* Macronutrient Magnesium is one of nine macronutrients and is taken up by plants in quantities similar to that of phosphorus (P). In plants, Mg is essential for many functions. It: • sets in motion (catalyzes) the production of chlorophyll and serves as the central atom in the chlorophyll molecule; • serves as a building block of ribosomes, the “factories” that synthesize proteins in cells; • stabilizes certain structures of nucleic acids, the molecules that transfer genetic information when new cells are formed; • activates or promotes the activity of enzymes, which are molecules that have specific shapes needed to set in motion certain chemical reactions necessary for proper growth and development of plants; • serves as an essential element to create adenosine triphosphate (ATP), the “battery” that stores energy in the plant; • ensures carbohydrates created in leaves are exported to other plant organs. Carbohydrates are used in plants for energy and for structure. Plants can only access Mg in the soil solution. Contributors to this Mg are: • redistribution from other areas, including: irrigation water, commercial fertilizer, manure, biosolids, and sediment deposition; • weathering of Mg-containing primary and secondary minerals like certain types of amphiboles, biotite, chlorites, dolomite, garnets, olivine, magnesite, phlogopite, some pyroxenes,serpentines, talc, and tourmaline; • release from the interlayers of the layer silicate minerals chlorite, smectites, and vermiculite; and • release (desorption) from surfaces and edges of layer silicate minerals, termed “exchangeable Mg.” Exchangeable Mg and Mg in the soil solution are the Mg forms measured by soil tests and are considered readily available to plants. Minerals containing Mg are more soluble in acid soils (below pH 7). In sandy soils with low numbers of exchange sites (location exchange capacity), dissolved Mg can move below the root zone because there are not enough edges and surfaces of layer silicate minerals to retain it in the upper levels of the soil. Therefore, levels of exchangeable Mg in acid, sandy soils can be too low to meet plant nutritional needs. When plant roots take up water, more water from farther away moves to the roots to replace that which was taken up. Magnesium that is dissolved in the soil solution moves with this water. This process, termed mass flow, is responsible for keeping the plant supplied with dissolved Mg. *Manganese (Mn) (IMMOBILE)* Micronutrient Manganese is one of the 17 elements essential for plant growth and reproduction. It is needed in only small quantities by plants, but like other micronutrients, Mn is ultimately as critical to plant growth as the major nutrients. *Molybdenum (Mo) (IMMOBILE)* Micronutrient Molybdenum is a trace element required in very small amounts for the growth of both plants and animals. Crop deficiencies of Mo are fairly uncommon, but there are a variety of soil and foliar fertilizers that can be used to correct this condition when it occurs. *Nickel (Ni) (IMMOBILE)* Micronutrient Nickel is the most recent element to be added to the list of essential plant nutrients. *Selenium (Se) (IMMOBILE)* Micronutrient Selenium is not essential for plants but is required for many physiological functions in humans and animals. Since Se is obtained primarily from food, its accumulation by plants impacts human health. *Silicon (Si) (IMMOBILE)* Micronutrient Silicon is generally not considered an essential element for plant growth. However, due to its important role in plant nutrition, particularly under stressful conditions, it is now recognized as a “beneficial substance” or “quasi-essential.” *Sulfur (S) (IMMOBILE)* Macronutrient Sulfur is used by plants in sufficient quantities that it is considered the fourth most needed fertilizer nutrient after the three macronutrients nitrogen (N), phosphorus (P), and potassium (K). Sulfur fertilization is increasingly common because higher-yielding crops are taking up and removing more S from the soil as harvested products. Due to a decrease in S emissions from industrial and transportation sources, S deposition from the atmosphere is much lower than a few decades ago. Maintaining an adequate supply of S is essential for sustaining high-yielding crops, as well as for animal and human nutrition. Soluble sulfate (SO 42- ) is the primary source of S nutrition for plants. Within the plant, S is required for protein synthesis. It aids in seed production and produces the chlorophyll necessary for plants to carry out photosynthesis. It is a necessary component of three amino acids (cysteine, methionine, and cystine) needed for protein synthesis. It is also required for nodule formation on root hairs of legume crops. Wheat grown in soils with low levels of available S result in lower-quality of grain protein, making the flour less suitable for bread making. Since both S and N are needed for protein formation, these two nutrients are closely linked. Crops have varied requirements for S compared with N and have a wide N:S ratio in the harvested product (table 1). For example wheat has a relatively low requirement of S, with an N:S ratio in a grain of 16:1. Canola has a high S requirement, with an N:S ratio of 6:1 in the seed. Sulfur is involved in a number of secondary plant compounds. For example, the characteristic flavor and smell of onions and garlic are associated with volatile S compounds. plant roots take it up. Common soil bacteria (e.g. Thiobacillus species) are responsible for converting elemental S to sulfate, but this process can take from weeks to years. Favorable conditions of soil temperature, moisture, pH, and aeration will speed this conversion to sulfate. Similarly, a small particle size of elemental S will enhance the rate of conversion. *Zinc (Zn) (IMMOBILE)* Micronutrient Zinc is a trace element and only required in very small amounts in the plant, Zn deficiency in crops is widespread around the world. Low Zn content in food crops contributes to Zn deficiency in approximately 30% of human diets. With the world population continuing to expand, it is critical that attention be paid to Zn nutrition in food crop production. *Acidity and Alkalinity* All the carefully applied homemade fertilizer in the world won't help plants that are not in their optimal pH range. If the soil is too acid or alkaline for the plant, it shuts down the plant's ability to access sufficient nutrients. In addition to fertilizing, check the pH to be sure your efforts aren't in vain. Increase acidity with vinegar and use wood ash to increase alkalinity. If these ingredients are used to provide a nutrient, be sure they are in balance with the pH needs of the plant.