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About potash


Potassium for high rainfall pastures in Western Australia

Potassium deficiency can lead to loss of clover content and severely limit production of high rainfall. Large amounts of potassium can be lost each year through leaching and removal of potassium in hay or silage. This page is specific to high rainfall pastures (more than 600mm average annual rainfall) in the south-west of Western Australia.

Soil tests provide a guide to potassium requirements and follow-up tissue testing can confirm plant potassium levels. The Department of Primary Industries and Regional Development recommends using nutrient testing to support fertiliser management decisions.

Tractor spreading fertiliser

Monitoring potassium in high rainfall pastures is important

Large amounts of potassium can move out of the root zone through leaching or plant uptake, especially in high rainfall (more than 600mm average annual rainfall) sandy areas. Potassium is removed in hay and silage and is redistributed around the farm by livestock, mosly in urine patches.

Pasture legumes – clovers in most Western Australian pastures – are very susceptible to potassium deficiency, which greatly reduces seed production. Legumes will gradually disappear from potassium-deficient pasture. Re-seeding legumes after adding potassium fertiliser may be required.

In beef-grazed sandy areas where potassium deficiency is common, potash is applied annually, often in addition to phosphorus fertiliser.

Potassium deficiency is rare in ryegrass, even in intensively grazed dairy pasture. Ryegrass has deeper roots and can explore more soil and access potassium at greater depths, especially if there is clay in the subsoil.


Soil test and tissue test

If the tissue test shows less than 2% potassium (K), it is likely the pasture will respond to potassium application.


Soil test Colwell K values and clover growth

Potassium soil analysis can be very strongly influenced by potassium in urine patches. We recommend you follow our soil sampling guidelines and check the soil test with a tissue test. Maintaining records of annual soil tests and comparing them to tissue tests will improve the ability to accurately assess potassium requirements. See Table 1 for a guide on using Colwell K values to estimate the need for potassium fertiliser.

Table 1 Clover pasture requirements for potassium fertiliser and response at different Colwell K values


When to apply potassium fertiliser

Apply split applications of muriate of potash (potassium chloride) in autumn and spring to provide a more even supply of potassium to leaching soils. This fertiliser is in addition to phosphorus and sulfur fertilisers or other fertiliser that is required.

Potassium deficiency on fertile clay or loam soils is less likely than on sands, and we recommend a single application of muriate of potash 4 to 8 weeks after the break of season, applied to emerging pasture. Potassium applied at this time is more likely to be absorbed by developed roots and less likely to be leached.

Use tissue testing to monitor the effectiveness of applied potassium.

 Application rates of potassium

These rates are guidelines only and will vary depending on pasture production targets and economics:

  • For a PBI* <300, 1kg of potassium is required for each unit increase in Colwell K required.
  • For a PBI* >300, 2kg of potassium is required for each unit increase in Colwell K required.
  • Deficient pastures with a PBI* <300 and a Colwell K of 40 would require 60kgK/ha.

* PBI is the phosphorus buffering index; see phosphorus for high rainfall clover pastures for more information.

A maintenance application of 30 to 50kgK/ha annually is likely to be required for high rainfall grazed pastures and 50 to 100kgK/ha for hay paddocks. We recommended that you soil test for an accurate assessment. The effectiveness of applications can be checked by tissue testing.

 Dairy pastures and potassium

Potassium concentration in some pastures can be high enough to induce magnesium deficiency in lactating dairy cows and this reduces productivity and health. Refer to Bulletin 4812 Managing potassium in dairy pastures.

 Making better nutrient management decisions

We encourage dairy, beef, sheep managers in the lower south-west of Western Australia to base nutrient management decisions on good evidence, and recommend regular soil testing and consultation with FertCare-accredited advisers to plan profitable and responsible fertiliser use.

Potassium for high rainfall pastures in Western Australia


Application of potassium to grass used as cover crop guarantees higher-quality cotton

In an article, Brazilian researchers show that besides simplifying operational logistics and improving production, fertilization of the grass used as a cover crop can reduce fertilizer use in the long run.


By Maria Fernanda Ziegler | Agência FAPESP – The use of cover crops between cotton harvests protects the soil, conserves water, and reduces the risk of erosion. Researchers at the University of Western São Paulo (UNOESTE) and São Paulo State University (UNESP) in Brazil found that application of potassium (K) to a grass cover crop grown before cotton in sandy soil lowered production cost and resulted in cotton with a higher market value.

“The dynamics of early application of potassium to grass planted as a cover crop before cotton results in more resistant fibers and a smaller proportion of short fibers than when the conventional method of applying the nutrient to the cotton crop is used. In addition to the improvement in quality, the technique reduces production cost for the farmer because of its impact on operational dynamics. The farmer can apply potassium once instead of twice. The technique saves labor and diesel oil, as well as optimizing operational logistics. In the long run, it’s also expected to reduce fertilizer use,” said Fábio Echer, a professor at UNOESTE and lead author of an article on the study published in Scientific Reports.

The two-year study, which was conducted on UNOESTE’s experimental farm, compared the conventional method of fertilizing cotton directly with two other methods, both involving early application of potassium. It also evaluated cotton growing without fertilizer and without a cover crop.

The research was funded by a master’s scholarship awarded by FAPESP to Vinicius José Souza Peres. The São Paulo State Cotton Growers Association (APPA) and Fundação Agrisus also collaborated on the project.

Quantitative and qualitative analysis of fiber

In one of the treatments, the researchers applied potassium to the grass cover crop in two doses (70 kg per hectare each). They compared this with application to the cover crop of a single dose of 140 kg per hectare and split application, with half going to the cover crop and the other half to the cotton. The results in terms of fiber yield were identical to those of the conventional method. Yield and quality were both lower with no fertilizer than when the conventional method or early application was used.

“The study included a calculation of fertilizer use efficiency,” Echer told Agência FAPESP. “We found that early application enabled the forage grass used as a cover crop to recover nutrients from the soil, in addition to the function of protecting it. This plant has a deep rhizosphere and its roots are able to find soil nutrients lost via leaching from previous crops, recycling them, and pushing them back to the surface. When the plant dries out, it releases potassium in the first rain to the crops that come next.”

The main advantage of early application, however, is that it increases the commercial value of the cotton produced. The analysis of fiber quality and cotton value found that fertilizing the cover crop with potassium led to a smaller proportion of short fibers, which depreciate the finished product, and also enhanced fiber fineness (micronaire), maturity and strength. “These characteristics are important. They represent higher commercial value for the production of finer cotton fabric, which is better quality and fetches a higher price on the market,” Echer said.

The improvement in quality relates to the availability of potassium in the soil and plant water status. “Cotton fiber is a cell, and like all cells it needs water to expand. By conserving more water in the soil and in the plant, we can also improve fiber size,” he explained.

Potassium plays a key role in the control of plant water loss. It regulates stomata functioning, carbon dioxide fixation, enzyme activation, and nutrient transport, as well as aiding stress tolerance. Soil potassium reaches plant roots mainly by diffusion, which accounts for 72%-96% of each plant’s requirement.

“Extreme weather events, high temperatures, and droughts have become more frequent because of global warming, and conservationist soil management techniques such as those suggested by the study can mitigate the adverse effects of all this on production,” Echer said. “Inconsistent rainfall may limit crop viability, and because only about 8% of Brazil’s cotton plantations are irrigated, the use of a cover crop is especially important. Straw mulch helps reduce soil temperature, which in turn helps conserve water.”

In western São Paulo, where the experimental farm used in the study is located, the temperature can reach 70°C on cotton plantations without a cover crop (and hence with exposed soil). The use of a cover crop keeps the soil at about 28°C-30°C, conserving soil moisture.

Early application of potassium is widely used in plantations with clayey soil, Echer added, but the technique had not yet been tested on sandy soil with little organic matter, making nutrient retention harder. “Farmers were reluctant to apply fertilizer early in the case of crops planted in sandy soil,” he said. “The study proves that applying potassium to the cover crop maintains yield and improves fiber quality even in sandy soil, which is more fragile, stores less water and makes potassium more susceptible to leaching.”

According to the researchers, the method analyzed in western São Paulo can be replicated in cotton plantations with sandy soil in Mato Grosso (the leading cotton producer in Brazil) and Bahia, as well as in other countries. “The cover crop can be different from the one we used in this study, because the climate may be different, but a precedent has been set for testing new cover species in other parts of the world,” Echer said.

The article “Potassium application to the cover crop prior to cotton planting as a fertilization strategy in sandy soils” (doi: 10.1038/s41598-020-77354-x) by Fábio Rafael Echer, Vinicius José Souza Peres and Ciro Antonio Rosolem can be read at:


Application of potassium to grass used as cover crop guarantees higher-quality cotton


Potassium As A Key Fertilizer In Combating Climate Change And Malnutrition

By Muhammad Yasir Khurshid

According to the Global Climate Risk Index, 2020, Pakistan is the 5th most vulnerable country to climate change and has paid a cost of nearly 10 thousand lives and 3.7 billion dollars to the national economy because of the ravages of climate change since the year 2000. Further worsening the situation, the future cost of the climate impact may increase to $14 billion per year over the next four decades (Eckstein et al., 2020). In recent years, Pakistan has witnessed the heatwave that resulted in the impairment of grain filling, especially in the Autumn Maize crop. Crop quality and nutrient status of the produce has also been deteriorating under such harsh conditions.

Climate change increases in local and global temperatures pose a significant threat to plant growth and crop production (Pareek, Dhankher and Foyer, 2020). If current rates of global warming continue, global temperatures will continue to increase by a further 1.5 °C between 2030 and 2052 (Intergovernmental Panel on Climate Change, 2018). Heat stress can impair all stages of plant growth from germination to reproduction, limiting the productivity of major staple food crops (Hussain et al., 2019). For example, heat stress has a negative impact on wheat yields. A 4–6% reduction in average global yields of wheat is predicted for each 1 °C increase in global mean temperature (Asseng et al., 2015). 

Another grave reality of the world is malnutrition as 1 in 9 people suffer from nutrient deficiency, resulting in stunted heights and poor human growth.  A healthy adult may require 3,400 mg of potassium on daily basis (National Institute of Health, 2019), and potassium fertilization at assures the concentration of K in wheat grains up to 5400 mg K/Kg (Hussain, 2020). According to FAO estimates, the world population will exceed 9 billion people by 2050. and world food production will have to be increased by 50% to meetup the requirements. Eradicating hunger on the planet and guaranteeing sufficient food production to feed an ever-growing world population are challenges that our society faces. For this, it is essential to increase agricultural production and the role that potassium fertilization plays in this regard is irrefutable.

Many of the environmental problems related to agriculture will continue to exist in the coming years. It is also important to not only mitigate the adverse impacts of climate change but also to feed the coming generations on a sustainable basis. Soils must be fertilized to maintain the adequate content of mineral elements that crops need for their correct development through their absorption at the precise moment and in the necessary quantities. Fertilized soils guarantee greater food production, cut the price of agricultural products, and improve the lives of the farmer and his environment. Scientists emphasized the importance of judicious use of potassium as a key fertilizer in combating the detrimental effects of global warming and changing climate in a conference organized by Engro Fertilizers and MNS University of Agriculture, Multan. Potassium plays many important roles that enable the crop plants to not only withstand the harsh climate and extremes but also play decisive roles in yield and production. Potassium strengthens the vascular bundle to transport water within the plant body, so it increases its resistance towards disease, especially under high temperatures.  

Potassium is an essential component in living beings and plays a fundamental role in the growth of plants. Potassium is indispensable for plant growth and yield building, and not just in low water or dry conditions, even under optimal growing conditions, potassium fertilization pays off. But, in a year of drought, it is even more effective: the plant is under stress and benefits even more from the positive effects of nutrients. Trials advocate the application of potassic fertilizer (Pettigrew, 2008) and highlight the prospects of potassium solubilizing microbes for yield enhancement (Ali et al., 2020). Value addition of potassium fertilizers to minimize the potash losses is a great challenge of the fertilizer industry. The specialty fertilizer industry transforms the mineral nutrients for value addition in many ways including polymer and microbial coatings which significantly reduces the nutrient losses and usability by the crop plants.   These nutrients are in forms that can be assimilated by plants.  It results in the form of increased production with high grain mineral contents but also improves the flavor, taste, and shelf life of the produce.  Sardans and Peñuelas (2015) has reviewed the functions of potassium in crop plants and connoted that potassium regulates the function of opening and closing of the leaf stomata and consequently transpiration of the plant. Thus, a good potassium supply makes it possible to reduce unproductive water losses. The potassium is important for photosynthesis and to promote transport of assimilates from photosynthesis to the roots and storage organs. Thus, it actively participates in good root growth, a key factor in building yield. With a more developed root system, which can absorb water from deeper layers of the soil, the plant will be able to withstand long periods of drought. Potassium increases the water holding capacity of the soil so that more water available to plants, their growth, formation, and performance. It directly influences photosynthesis through action on chloroplasts and indirectly through its influence on the stomata closure mechanism. It participates in the activation of more than 50 enzymes in the metabolism of the plant, thus it Improves the formation of carbohydrates such as sugar and starch, and facilitates the transport and storage of carbohydrates from the leaves to the storage organs.  Incorporation of potassium also enhances the uptake of Zn with up to 75 % increment in Zn contents in grains (Hussain et al., 2020). Thus, the use of potash not only increases the chances of survival under changing climate conditions but also imparts high resilience in terms of crop productivity for the coming generations.  The use of value-added potassium fertilizer will assure the cost-cutting due to curbing losses and increase productivity, and it is a frontline weapon in combating with devouring threat of climate change.



Ali, A. M., Awad, M. Y., Hegab, S. A., Gawad, A. M. A. E., & Eissa, M. A. (2020). Effect of potassium solubilizing bacteria (Bacillus cereus) on growth and yield of potato. Journal of Plant Nutrition, 1-10.

Eckstein, D., Künzel, V., Schäfer, L., & Winges, M. (2020). Global Climate Risk Index 2020: who suffers most from extreme weather events? Weather-related loss events in 2018 and 1999–2018. Germanwatch, Bonn.

Hussain, S., Shah, M. A. A., Khan, A. M., Ahmad, F., & Hussain, M. (2020). Potassium Enhanced Grain Zinc Accumulation In Wheat Grown On A Calcareous Saline-Sodic Soil. Pak. J. Bot52(1), 69-74.

National Institutes of Health. (2019). Potassium Fact Sheet for Health Professionals.

Pareek, A., Dhankher, O. P., & Foyer, C. H. (2020). Mitigating the impact of climate change on plant productivity and ecosystem sustainability. Journal of Experimental Botany, 71(2), 451-456.

Pettigrew, W. T. (2008). Potassium influences on yield and quality production for maize, wheat, soybean and cotton. Physiologia plantarum133(4), 670-681.

Sardans, J., & Peñuelas, J. (2015). Potassium: a neglected nutrient in global change. Global Ecology and Biogeography24(3), 261-275.

Potassium As A Key Fertilizer In Combating Climate Change And Malnutrition


Potassium chloride in Pfizer-BioNTech Covid-19 vaccine is not dangerous

Copyright AFP 2017-2020. All rights reserved.

Social media posts claim the Pfizer-BioNTech Covid-19 vaccine is “poison” because it contains potassium chloride -- a chemical also used to stop the heart during a process of lethal injection. The claim is false; the coronavirus vaccine was tested for safety in clinical trials, and medical experts say the minimal amount of potassium chloride used in the shot will not harm recipients.

“Pfizer’s vaccine got the same poison, that they use with USA lethal injections at the prisons. It’s called POTASSIUM CHLORIDE,” claims a December 20, 2020 tweet.

A December 18, 2020 tweet, also calling the vaccine “poison,” includes an image of the product information for the Pfizer-BioNTech shot along with the text, “Pfizer’s Covid-19 vaccine comes with potassium chloride - the same drug used for executions of death row inmates!”

Screenshot of a tweet taken on January 6, 2021

The image can be found on Instagram, including in one post claiming, “It’s a cocktail of poison y’all!!!”

It was also shared hundreds of times on Facebook as the United States and Canada approved the Pfizer-BioNTech Covid-19 vaccine for emergency use in December amid rising numbers of coronavirus infections. 

However, potassium chloride is a natural substance, regulated by the human body.

Libby Richards, associate professor at the Purdue School of Nursing, told AFP by email: “Potassium chloride is found in almost all of the food we eat -- meats, fruits, cereals, chips, baby formulas. 

“If you drink bottled water, you are drinking potassium chloride which is then absorbed into your bloodstream.” 

Asked about its use in vaccines, Richards said: “The ingredients in vaccines are carefully chosen and very closely monitored for safety. 

“The amount of potassium chloride found in vaccines is very, very small and absolutely considered a safe amount.”

According to the US Food and Drug Administration, each dose of the Pfizer-BioNTech Covid-19 vaccine contains .01 milligram of potassium chloride.

That is “equivalent to a pinch of salt,” Scott Halperin, director of the Canadian Centre for Vaccinology, explained by phone.

Halperin, who teaches at Canada’s Dalhousie University, said that potassium chloride is used in many vaccines because it is a salt, and “when making a viral vaccine, you need to have the proper amount of salts to keep cells alive. Because it’s a natural product that all cells need, it’s also put into cell cultures.”

Pfizer-BioNTech was the first to complete a large-scale, phase 3 clinical trial for a Covid-19 vaccine on patients older than 16. It was found to confer 95 percent protection against the virus with no serious safety issues. 

Both the US Centers for Disease Control and Prevention and Health Canada are carefully monitoring all adverse effects to the vaccine as it is offered to larger portions of the population.

AFP Fact Check previously reported on misleading claims about potassium chloride in vaccines here. More reporting on misinformation surrounding the Pfizer-BioNTech Covid-19 vaccine is available here.

Potassium chloride in Pfizer-BioNTech Covid-19 vaccine is not dangerous


Potassium Deficiency in Cotton a Concern for Producers

 DECEMBER 28, 2020

Potassium deficiency in cotton across the Southeast is a major problem for producers, even more so this year, says Glen Harris, University of Georgia soil fertility and Extension specialist.

Glen Harris

“It’s been a continuing problem. In my opinion, I think we do a decent job with nitrogen. We don’t seem to have a lot of phosphorus problems. Potassium is probably our No. 1 nutrient issue every year,” Harris said. “It kind of comes and goes but this seemed to be one of those years where we saw a lot of it.”

Why Does it Happen?

Theories vary on why the nutrient came up short this year in cotton plants. Some believe the rainfall in the late summer and fall contributed to its deficiency, especially since it is mobile in the soil. However, Harris said it is not as mobile as nitrogen and we have experienced decent rainfall in prior years and did not have unusual potassium.

“I really wonder if there’s other things going on. I think part of it is, we’re seeing higher calcium levels and I think that’s starting to interfere with potassium uptake,” Harris said. “People for some reason are running their pH’s higher which also usually comes with higher calcium levels. Calcium competes with magnesium to get into the plants. That’s a theory, but I’m wondering if that had something to do with it.”

Potassium’s Importance

Potassium is one of the primary nutrients plants need to grow.

“Carbon, hydrogen and oxygen are the top three, but we don’t talk a lot about those because we get them free from air and water. The next three are N (nitrogen), P (phosphorous), K (potassium) and I rank them N-first, K-second, probably for Georgia cotton as far as need,” Harris said.

Potassium deficiency itself is detrimental to the plant. But it could also lead to secondary problems like the fungal disease leaf spot.

“If you read the textbook, it’ll say the older leaves will turn yellow and eventually turn yellow around the outside like dead tissue around the edge of the leaf. My experience has been, it’ll occur almost on the leaves of the whole plant. We also get leaf spots that will come in, too,” Harris said. “We’ve seen enough of it over the years, people are pretty good at diagnosing it, which is also kind of scary because we think we know what to do to avoid the problem and we know what it looks like when it shows up, but we keep getting it. That is concerning.”

How to Avoid Potassium Deficiency

There are various ways to combat this nutrient deficiency. Do not wait too late to apply potash. Soil test and grid sample, since most of the time, these instances will occur in patches in the field. Also, do not split your fertilizer applications. Apply all at planting.

Clint Thompson

Clint Thompson

Multimedia Journalist for AgNet Media Inc.


Potassium Deficiency in Cotton a Concern for Producers


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