# Potassium (K) *Potassium Fertility and Soils in SE New England (1st in a series of quick follow up articles after our SNEACTS 2025 Conference Workshop)* By [Brix & Mortar](https://paragraph.com/@brixbounty) ยท 2025-02-13 --- Potassium (K) is positively charged cation, possessing a single positive charge per ion. Potassium is not held well on soil colloids; which will be populated by calcium and magnesium in well limed soils; although our parent rock material in our soils in SE New England often contains high amounts of potassium, the annual "recharge" rate is often not enough to maintain optimum potassium levels in our soils for maximizing yields. Therefore it is a common practice to add potassium fertilizers for top yields and crop health. The amount of potassium fertilizers added will depend on soil test results and how "hungry" your crops are for potassium. Potassium loving crops include "fruits and roots" - beets, carrots, cucumbers, potatoes, tomatoes as well as high biomass crops like celery. **Potassium Fertilizers - Potassium Fertilizer reported in K20** * Potassium Sulfate (0-0-50 with 17% S) * Sul Po Mag (0-0-22 with 11% Mg and 22% S) * Green Potash (15% K) a blend of seaweed and zeolite from Fertrell (via Progressive Grower) A note about compost often contains an abundance of potassium, and if you are adding significant amounts of compost to your soils, then you may be meeting your crops potassium needs through compost. In fact, sustained use of compost as a primary fertility source may lead to potassium excess. **If you are saturating the soil with high levels of potassium, make sure you are maintaining optimum calcium and magnesium levels as well for the best quality crops.** **I can't put enough emphasis on this point; when fertilizing for optimum K levels its critically important to maintain adequate Ca and Mg levels if you are attempting to grow high quality crops.** At Brix Bounty we typically add a baseline of 100# Potassium to our soils each year, and double this rate for the highest K demand crops; if we are doubling the rate, we'll be sure to include sulpomag to balance mg availability with the heavy application of potassium. * Example - Applications of 1 ton Kreher's 5-4-3 and 100# Potassium Sulfate will supply ~110# K20 In dry soils potassium may get "locked up", so we will also ensure abundant K levels for dry summers > see this article for an excellent discussion > [https://nutrien-ekonomics.com/news/crop-potassium-deficiency-under-challenging-conditions/](https://nutrien-ekonomics.com/news/crop-potassium-deficiency-under-challenging-conditions/) Potassium's also plays a critical role in a plant's Water Use Efficiency; further enhancing its importance in a dry growing season. Finally, because potassium is mobile in soils and isn't held well in limed soils; we'll keep potassium sulfate on hand for the occasional wet season, and will side dress potassium sulfate for long season or high K demand crops if we receive excessive rain events which may lead to potassium leaching. **Actions** * Take annual soil tests to measure potassium levels in your soils to determine the baseline potassium needs for all crops. * Understand the Potassium fertility requirement of different crops you are growing. * Trial different potassium rates for one or two crops this season and observe crop health and measure yields. Example split a bed in two and add 100# Potassium vs 200# Potassium and see if you notice a difference in crop health and/or yield. Tip: it's easiest to measure yield differences with single harvest crops like carrots or potatoes vs the record keeping for tomatoes or zucchini. * If you are growing high yielding cucumbers and tomatoes in tunnels; play extra attention to potassium fertility as these crops require abundant K for optimum yields; there are heaps of resources online re potassium fertility for tunnels. **Potassium Resources** [ library:articles:potassium\_basics - Spectrum Analytic ------------------------------------------------------ Potassium is represented by the letter K, which is the first letter of Kalium, the Latin word for potassium. The term "potash" is often used to refer to potassium chloride (KCl), a common potassium fertilizer. The word potash is derived from "pot ashes" which refers to the practice of using the leachate of wood ashes as a source of potassium. https://spectrumanalytic.com ![](https://storage.googleapis.com/papyrus_images/2c9b21015028f431fa2b3a7271397bea.jpg) ](https://spectrumanalytic.com/doc/library/articles/potassium_basics) [ Phosphorus, Potassium, Calcium, and Magnesium --------------------------------------------- Calcium (Ca) is usually supplied in sufficient quantities by liming if appropriate liming materials are chosen (see Soil Acidity, pH, and Liming in the next section). If soil pH is high and Ca is needed, it can be supplied without affecting pH by applying calcium sulfate (gypsum) which contains 19-23% Ca. https://nevegetable.org ](https://nevegetable.org/cultural-practices/Phosphorus-Potassium-Calcium-Magnesium) "**Improving agricultural water use efficiency by nutrient management in crop plants"** [https://www.tandfonline.com/doi/full/10.1080/09064710.2010.491954#d1e1073](https://www.tandfonline.com/doi/full/10.1080/09064710.2010.491954#d1e1073) **"Field, plant, to leaf: A meta-analysis on crop water use efficiency response to potassium fertilization"** [https://www.sciencedirect.com/science/article/abs/pii/S0022169423005206](https://www.sciencedirect.com/science/article/abs/pii/S0022169423005206) --- *Originally published on [Brix & Mortar](https://paragraph.com/@brixbounty/potassium-k)*