Understanding PHOSPHORUS and POTASSIUM in your Fertility Program
By Dylan Rogers, AgroLiquid Sales Account Manager
This article was taken directly from the Winter 2019 AgroLiquid Newsletter.
In agriculture, there are always a few factors that are out of our control - specifically Mother Nature. This proved to be true in 2019 with widespread flooding and extreme temperatures - both highs and lows. Focusing on the factors we can control will ensure we make the best possible crop, regardless of what Mother Nature throws our way. Understanding how phosphorus and potassium fertilizers interact with other inputs and elements in the soil will help growers decide which inputs and application timings best suit their particular operation.
Phosphorus (P)
Phosphorus (P) is an essential plant nutrient and very important for numerous plant processes and crop production. It is a vital component of DNA and RNA, the building blocks of proteins and protein synthesis. The adenosine triphosphate molecule (ATP) is responsible for storing and transferring all of the energy produced and needed by the plant. At the cor of this ATP molecule are phosphates, responsible for all the activity of ATP. Phosphorus also plays a major role in the stimulation of new root growth.
"Tie up" within the soil is the primary concern with phosphorus fertilizers. In acidic soil conditions, calcium will be the major component of phosphorus tie up. Phosphorus is most available to the plant in a soil pH range of 6.3-6.8. Common liquid fertlizers, such as ammonium polyphosphate (10-34-0) and orthophosphate (9-18-9), applied in the early spring will also have a likely chance of being tied up if a gypsum application was made in the fall.
Choosing a phosphorus fertilizer that is protected from tie up will ensure that you get the most out of your fertilizer investment and that your crop will receive the required amount of P needed.
Potassium (K)
Potassium (K) is also an essential plant nutrient responsible for many vital processes within the plant. It plays a major role in plant water relations and photosynthesis. K regulates the opening and closing of the stomata, in turn regulating the uptake of Carbon dioxide (CO2) from the atmosphere, an important aspect of photosynthesis. Potassium is also responsible for the translocation of sugars within the phloem, and other nutrients and water within the xylem. Potassium must be in adequate supply for the plant to function properly and produce the best crop possible.
Potassium and sodium have a unique relationship that is many times overlooked. The use of poor-quality, well water in many areas has caused sodium levels to build up in the soil. In these situations, the soil solution will contain more sodium ions than potassium ions. These two ions are "look alike" ions and the plant will not discriminate against which one it takes up. An excess of sodium in the soil solution will tend to induce a potassium deficiency in the plant. This is an important aspect to address in your growing operation.
It is also important to understand the solubility of potassium fertilizers. For example, Sulfate of potash (SOP) is a great tool, often used in California for building soil potassium levels. However, it is important to recognize how much is actually going to be available to the crop. For example, dry SOP has a solubility of around 6%. A 500-pound application of 0-0-50 will deliver 250 pounds of K20, so at 6% solubility, only about 15 pounds of K20 will be immediately available to the crop. Over time, with precipitation or irrigation, more of the K20 will become available. Supplementing this with an in-season, highly soluble, liquid potassium fertilizer is a great way to ensure your crop will get the large amount of potassium it requires. Of course, not all liquid potassium sources are created equal. Some potassium fertilizers are high in chlorides and other salts that can be toxic to plant health. Growers will want to choose a potassium source that is free of chlorides.
Having a better understanding of how phosphorus and potassium fertilizers interact in the soil and with other inputs will help growers get more out of their fertilizer investment this coming season. Choosing a phosphorus fertilizer that is protected from tie up and a potassium fertilizer that is highly soluble and free of chlorides will ensure healthier plants to achieve 2020 yield goals.
Sure-K and Kalibrate
Sure K® and Kalibrate® are clean, chloride- and hydroxide-free potassium solutions. Each can be applied in combination with other crop production or protection products and present a very low risk of crop injury. The unique formulations of these products provide increased crop utilization, allowing lower total product application volume to produce the same results as other conventional potassium fertility products when applied at typical rates. Contact your AgroLiquid representatives to find out which is right for your situation. [See more about Sure-K and Kalibrate.]
Pro-Germinator/PrG
Pro-Germinator® is used primarily for the application of phosphorus, but is partnered with nitrogen, potassium, and micronutrients for maximum performance. Pro-Germinator, through Flavonal Polymer Technology, contains both orthophosphate and carbon-protected polymer phosphate to provide readily available and controlled-release phosphorus with minimal danger of tie up in the soil. [See more about Pro-Germinator.]
This article was taken directly from the Winter 2019 AgroLiquid Newsletter.
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