Phosphorous is important to plant growth in many different ways. It plays a major role in the early root formation and growth of the plant. Later, you will see greater flowering and seed production and better quality. Phosphorous also helps growth in cold temperatures and water-use efficiency. Plants need adequate supplies of P for their structural components of proteins, enzymes, nucleic acids and DNA. Proper photosynthesis and respiration depend on P availability to the plant.
Potassium is needed by plants for various functions that take place. Most importantly, K plays a major role in photosynthesis and plant food formation. It also helps a plant respond better to drought conditions by helping to control a plant’s cell turgor. Studies show that proper levels of K available to the plant improve that plant’s ability to combat disease and insect damage. Lastly, Potassium plays a role in the production, transport and storage of sugar and carbohydrates and also in proper cell wall production.
Soil pH should be the first consideration when evaluating a soil test because it is the basis for most soil chemistry and nutrient reaction. A pH test measures the soil acidity (values below pH 7.0) or alkalinity (values above pH 7.0). Nutrient availability and plant growth can be affected by very small changes in a soil’s pH level.
Buffer pH (BpH)-
Buffer pH levels are values generated in the laboratory in order to generate lime recommendations. The difference between the pH level and the Buffer pH level indicates how easily the soil will be changed when applying lime. If the difference between the two levels is large, very little lime will be needed because the reaction of the soil shows that a little will go a long way. If the difference between the pH level and BpH level is small, more lime will be needed to reach the desired pH level.
Cation Exchange Capacity (CEC)-
After running soil through our laboratory, a CEC value is calculated that represents the soils ability to attract, retain and exchange cationic elements. Cationic elements, such as: potassium, ammonium, magnesium, calcium, zinc, manganese, iron and copper, have a positive charge and are therefore attracted to the negatively charged soil. When the soil tests indicate a higher CEC level, the soil has the ability to hold a greater capacity of cations. High CEC levels with good test results mean a large nutrient reserve for each plant. High CEC levels with poor test results may take a large amount of fertilizer or lime to correct the soil and make the cations available for the plant’s usage.
Base Saturation is the total percentage of the soil exchange sites (CEC) occupied by basic Cations; Potassium (K), Magnesium (Mg), Calcium (Ca) and Sodium (Na). Optimum levels of each are as follows:
As Base Saturation increases, so does the availability of the soil Cation nutrients. The Base Saturation number should be used as a guide to maintain optimum fertility levels.
Magnesium is a component of several minerals that are unavailable to the plant except in its ionic form. As pH levels rise, Mg becomes more available to the plant. Magnesium is essential for many plant functions: photosynthesis, sugar synthesis, nutrient uptake control, and the transport of phosphorus and starch. Mg is a major Cation and its availability plays a part in your soil’s CEC levels.
Calcium is usually present in the soil in adequate amounts, but most are unavailable to the plant. Only in its ionic state is it available for plants to use. Thus, CEC levels are important in Calcium’s availability to plants. Its main functions include: aiding in the uptake of nitrates, proper division and elongation of the plant’s cells, and it also aids in the development of the cell wall.
Sulfur is located in the topsoil. In order to be of use to a plant, it must be converted to Sulfate (SO4). In order to do this, soil conditions must be warm, moist, and well drained. As Sulfur is converted to Sulfate it leaches through the soil. As the plant’s roots reach this area, it is then available to the plant for many functions. Sulfur is necessary for the formation of chlorophyll, it aids in a plant’s growth and seed formation and in the processes of producing proteins, amino acids, enzymes and vitamins. It also aids in a plant’s ability to resist disease.
Boron ranges in the soil can be anywhere from 20 lb./acre to 200 lb./acre, but very little is actually available to be used by the plant. It is only of use when it is in the form of an inorganic borate complex of Ca, Mg or Na. Boron has been shown to improve yields dramatically, but the difference between applying a correct rate and a toxic rate is very close indeed. Applicators must be diligent in uniform mixing and applying the correct rate to crops, as some are much more sensitive to Boron than others. With that being said, Boron is critical for high yields and quality crops. Cell wall strength and development, cell division, fruit and seed development, sugar transport, and hormone development are all dependent on available Boron being present. It is needed for protein synthesis and is associated with increased cellular activity that promotes maturity. Boron also affects nitrogen and carbohydrate metabolism and water flow in the plant.
Copper is classified as a micronutrient because only a small amount is needed. An over-application can have a damaging effect for many years, so records should be kept of amounts applied to each field. Copper is the most immobile of all micronutrients. When root growth is inhibited, the uptake of Cu will also be inhibited. Copper is key to a plant’s elasticity and strength. It also plays a major role as a catalyst in photosynthesis and respiration. It is important in the building and converting of amino acids to proteins.
Manganese, to be used by a plant, must be in tandem with Iron. Rule of thumb: 2 parts Mn to 1 part Fe. As Sulfur content of a plant diminishes, so does the Manganese content. Mn is more readily available in Low soil pH than in High soil pH. It is thought to be the electric charge that every plant needs. It plays a large role in the assimilation of carbon dioxide in photosynthesis, activates fat forming enzymes, plays a part in the electron transport during photosynthesis and it aids in the synthesis of chlorophyll and in nitrate assimilation.
Zinc is a micronutrient and very little is needed by a plant in order for it to be effective. Zinc’s specific role in plant development is not known. But we do know that for certain enzymes to do their jobs, Zinc is very much needed. Zinc must be present to activate enzymes in protein synthesis, starch formation and proper root development. It is also necessary for the formation of chlorophyll and carbohydrates. An essential growth hormone, Auxin, needs Zinc in order to be produced. Toxicity levels of Zn are very rare under normal field conditions.
Organic Matter is a vast array of carbon compounds available in soil made from decomposed plants, microbes and other organisms. It plays a major role in your CEC levels by increasing the nutrient holding capacity of the soil. OM also acts as a binder for nutrients so that many become more readily available to plants. OM can be categorized into two groups; Active and Stabilized. Active OM is slowly decomposing in the last few decades. Stabilized OM is the complex compounds that have transformed over decades, which are highly decomposed and are very stable.