Fertilizer International 516 Sept-Oct 2023
30 September 2023
Low-chloride options and market drivers
LOW-CHLORIDE CROP NUTRITION
Low-chloride options and market drivers
Applications of chloride-containing fertilizers need to be carefully managed for crops such as berries, broad beans, citrus fruits, nuts, potatoes and stone fruits. Selecting chloride-free nutrient sources instead can offer distinct advantages.
Potassium chloride – a valued commodity
Potassium chloride (KCl, muriate of potash, MOP) has a number of well-known natural advantages as a fertilizer. It is widely available, relatively low-cost and readily soluble in water. Equally importantly, it has the highest potassium content (60-62% K2 O) of any of the mineral forms of potash.
Potassium chloride delivers K to plant roots both quickly and effectively, and also mixes well with other nitrogen and phosphate fertilizers. Indeed, the evidence suggests that the use efficiency of N and P fertilizers improves when applications are combined with K.
Potassium plays a key role in photosynthesis and the formation of sugars. It also has a direct role in protein synthesis and is therefore an essential element for cell growth and development. Potassium is also an important nutrient when it comes to mitigating the effects of salinity, cold, frost, waterlogging, drought and other stresses on crop production. It also offers protection against insects, pests and various diseases1 .
In contrast, the chloride component of KCl benefits some crops but can have an adverse effect on others.
Crops exhibit a range of responses to chloride. Typically, MOP and other chloride-containing fertilizers can be applied at rates of up to 140 kg of Cl per hectare with no negative effects on crop growth or yield2 . However, careful or restricted applications sometimes become necessary for a limited number of chloride-sensitive crops – especially when exacerbated by factors such soil salinity and salt stress.
Soil salinity – a growing problem
Salinity is a major problem for world crop production, according to the FAO, affecting about 20 percent of cultivated land and 33 percent of irrigated land globally. In total, more than 833 million hectares of soils worldwide are salt-affected currently.
The area of salt-spoiled irrigated land has increased from 45 million hectares to more than 62 million hectares in two decades – with damaging agricultural, environmental and economic consequences. The annual cost in lost crop production from saline land degradation caused by irrigation has been estimated at $27.3 billion globally, equivalent to an economic loss of $441/ha.
Chloride levels and salinity in soils can become elevated due to one or more of the following:
- Use of saline irrigation water
- Influx of seawater into groundwater in coastal areas
- Poor soil drainage due to either a lack of rainfall or lack of leaching
- Overuse of chloride-containing fertilizers (KCl, NH4 Cl, NPK 15-15-15 etc.).
In recent years, interest has grown in the management of fertilizer use under saline conditions due to increasing agricultural use of saline water and recycled sewage water. Irrigation water containing less than 150 mg/litre of Cl can be used on most crops. Salinity does become problematic, however, if it starts to disrupt plant nutrient uptake and translocation by:
- Raising the total ionic strength of the soil solution
- Increasing competition between nutrients and Na+ and Cl- ions.
This can lead to sodium-induced calcium and/or potassium deficiencies and chloride-induced inhibition of nitrate uptake. Phosphorus uptake by plants is similarly suppressed under saline conditions2 .
Chloride – the good and the bad
Chloride is required by plants for photosynthesis, fluid pressure control (osmoregulation) and for specialist parts of the leaf (stomatal guard cells) (Fertilizer International 471, p39).
Although chloride application is rarely needed at rates over 10 kg/ha, relatively large amounts of Cl are essential for some crops such as kiwifruit and sugar beet. Oil palms and coconut plants also need Cl to help the outer layer of their leaves to function (charge balance in guard cells)2 .
Yield response to chloride varies widely (Figure 1) with some crops exhibiting a high degree of tolerance. Sugar beet is one crop that requires large amounts of chloride to flourish, and shows higher yields with increasing chloride applications up to soil concentrations of 1,600 mg/kg1 .
Wheat and other cereals can be sensitive to chloride deficiency. This makes potassium chloride applications beneficial in areas such as the US Great Plains and the Canadian Prairies where soil chloride is often below critical levels. In contrast, the excessive application of chloride-containing potash can hurt US soybean yields, according to recent research by the University of Minnesota.
Critical soil Cl toxicity concentrations for different crops are shown in Figure 2. While chloride deficiency can occur in crops with high Cl requirements (e.g., kiwi fruit, palms and sugar beet), chlorine toxicity is much more common as a limiting factor in crop growth worldwide, particularly in arid and semi-arid environments. A critical chloride toxicity threshold of 15-50 mg/g and 4-7 mg/g have been reported for chloride-tolerant and chloride-sensitive crops, respectfully2 .
As a general rule, non-woody plants are less susceptible to Cl toxicity than woody plants, such as citrus trees, and bean crops2 . Relatively insensitive crops such as rice, wheat, sorghum, cotton, tomatoes, aubergines, bananas and peaches, meanwhile, can tolerate Cl in fertilizers at rates of 1,350-1,800 kg/ha each season1 .
Application rates of chloride-containing fertilizers such as MOP do need careful management for other crop types. Chloride applications for crops with a moderate chloride tolerance, such as soybean, pea, strawberry, peanut, apple and sugarcane, should typically fall within the range of 675-1,350 kg/ha. Other crops, especially pepper, cabbage, lettuce, rape, tobacco, potato and sweet potato, are more chloride sensitive and Cl applications should not exceed 675 kg/ha each season1 .
The presence of chloride in sprinkler irrigation water can also result in foliar injury in some crops (Table 1.).
Selection of a fertilizer with a lower salt index (Table 2) is one option for chloride-sensitive crops, particularly under saline growing conditions. This lowers the risk of salt burn and damage to seedlings and young plants.
Chloride-free potassium fertilizers
Popular chloride-free alternatives to potassium chloride (Fertilizer International 488, p48) include:
- Potassium sulphate (K2 SO4 , SOP)
- Potassium nitrate (KNO3 , NOP)
- Potassium magnesium sulphate (K2 Mg2 (SO4 )3 , SOPM)
- Polyhalite (K2 Ca2 Mg(SO4 )4 .2H2 O)
- Monopotassium phosphate (MKP, KH2 PO4 )
Of these potash alternatives, potassium sulphate (SOP) and potassium nitrate (NOP) are the most widely produced and applied by growers currently. Although sold at a premium, both can offer crop yield and quality advantages over MOP for specific crops under certain growing and soil conditions.
While MOP may be the preferred potash fertilizer for cereals and oilseeds, SOP is favoured for more chloride-sensitive, higher-value cash crops, notably fruits, vegetables, tobacco and tree crops. The other obvious advantage of SOP, as a sulphur source, is that it can be applied to address sulphur deficiency.
Total global SOP production capacity is around 11.2 million tonnes, according to some estimates, although actual production is around 6.6-7.3 million tonnes annually. SOP demand divides regionally between:
- China – 62 percent
- Europe – 17 percent
- The Americas – nine percent
- Middle East and Africa – seven percent
- South Asia, Southeast Asia and Oceania – three percent.
Outside China, Tessenderlo Kerley International (GranuPotasse, SoluPotasse, K-Leaf), K+S Group (KALISOP), and Compass Minerals (Protassium+) are the leading SOP producers. Major Chinese producers include Xinjiang-based Luobupo and Migao Corporation (Fertilizer International 488, p48).
SOP remains the cheapest low-chloride source of potassium, according to Tessenderlo Kerley International. The ability to supply plant-available sulphur is becoming increasingly valued too. Sulphur fertilization is particularly important in crops with a high sulphur demand such as brassica, canola and onions.
Potassium nitrate (NOP) offers a chloride-free source of both potassium and nitrogen. It can be soil applied as prills and is also widely used as a water-soluble fertilizer in irrigation systems (fertigation) and foliar sprays. Global production capacity stands at around 5.5 million tonnes currently. Major NOP producers include SQM (Qrop KS, Ultrasol K Plus), Haifa Group, Yara, KEMAPCO and Migao Corporation (Fertilizer International 488, p48).
NOP offers crop benefits during critical growth stages, such as during the booting of rice or tuber-bulking in potatoes, for example. Its nitrate content is also associated with improved water use efficiency and greater nutrient uptake (K, Ca, Mg) during fertigation (Fertilizer International 503, p56).
How big is the low-chloride crop nutrition market?
The global SOP market is forecast to grow by around four percent over the next decade or so, from 7.1 million tonnes currently to 7.4 million tonnes by 2035, according to Argus. Demand growth will be led by Europe (+4.0%) followed by Africa and the Middle East (+3.1%), the Americas (+1.1) and China (+0.5%).
However, there is a widely-held view that the SOP market is supply-constrained with market growth partly limited by supply and availability. Unmet demand for SOP does exist in the market, according to Tessenderlo Kerley International: “We believe that SOP market growth is probably constrained by supply. The supply/ demand balance remains very tight – it is difficult to supply all demand – [and] if there was more product on the market it would almost certainly be consumed. So, potentially, growth could be higher if more production was available.”
Historically, the ability of SOP – and other MOP alternatives – to provide a chloride-free form of potassium to crops has undoubtedly been a key market driver, as CRU have commented previously (Fertilizer International 475, p49):
“Although the potassium requirement of crops is the most fundamental determinant, it’s really the cultivation of chloride intolerant and chloride-sensitive crops which is the core driver of SOP demand. MOP, the cheapest form of potash, contains high levels of chloride which can be harmful to the yield and quality of many crops.”
Two concepts in particular – demand elasticity and unmet demand – can help predict the potential market size for low-chloride crop nutrition products.
While chloride-free potassium fertilizers are the only viable option for highly chloride-intolerant crops, they are optional choices for less chloride-sensitive crops – and therefore will only be selected by growers if the yield and quality improvements justify the extra costs involved. Because of this, the agricultural market requirement for chloride-free potassium can be split between ‘inelastic’ demand from chloride-intolerant crops and ‘elastic’ demand from other less chloride-sensitive crop types (Fertilizer International 475, p49).
Previously, CRU has estimated the demand potential for chloride-free potassium sources in more than 180 countries globally. This was based on a model that combined crop acreages and yields with crop-specific potash removal rates and a chloride-sensitivity value for each crop type (Fertilizer International 475, p49).
Results suggest that low-chloride crop demand is mainly linked to around 10 crop types in five key countries (Figure 3):
- China: potatoes, tomatoes and beans l India: potatoes, mangoes and peas
- United States: almonds, potatoes and citrus
- Russia: potatoes, sunflower seeds and apples
- Brazil: citrus, tobacco and beans.
China emerges as the country with the greatest potential for low-chloride crop nutrition, accounting for about a third of the world’s total potential for chloride-sensitive potassium demand. Russia, Brazil and Nigeria also show high demand potential for low-chloride sources of potassium, based on the chloride-sensitive crops grown in these countries (Fertilizer International 475, p49).
“Cultivation of chloride-sensitive and intolerant crops has grown very rapidly in areas of significant population growth, such as Africa, South Asia and Southeast Asia – we think there’s a lot of future potential in these regions. In addition to India, countries which appear to be significantly under-consuming SOP appear to be Russia, Brazil and Nigeria to name just a few.” commented CRU.
Similarly, an analysis in 2019 by Sirius Minerals, the former owner of the Woodsmith polyhalite project in the UK, identified significant unmet global demand for chloride-free potassium. They calculated that chloride-sensitive crops were responsible for 32 percent of total potash consumption, yet the actual supply of chloride-free potassium fertilizers to these crop types was much lower at only nine percent.
Their analysis suggested that, globally, 23 percent of potential low chloride potassium demand in the market was therefore unmet. If completely fulfilled, this potential shortfall could translate to around 70 million t/a of polyhalite demand, for example. This calculation was, however, clearly a scoping estimate and not a prediction or demand forecast by the company.
Attractive to new entrants
Potassium chloride (MOP) accounts for around 95 percent of the global potash market. The SOP market, while much smaller at seven million tonnes annually, is far more lucrative with products traditionally selling at large premiums (>$200/t) over MOP. In mid-July, for example, SOP was trading at $630/t Northwest Europe versus $330/t for MOP Vancouver.
The combination of a supply constrained SOP market and attractive price premiums has attracted new entrants. In Western Australia, two well-advanced SOP projects, Lake Way and Beyondie, were competing to enter production in the second half of 2021 – pursuing long-held ambitions to make Australia an SOP production centre and export hub for the Asia-Pacific region.
As Andy Hemphill, potash analyst at ICIS, commented in May 2021: “The chequered flag is being unfurled as the race to be first to market with potassium-rich sulphate of potash (SOP) fertilizer drawn from the barren wastes of Western Australia nears its conclusion. Producers are keen to take advantage of an expected wave of demand for SOP and high-potassium blended fertilizers over the coming years – with a particular focus on China, and the growing Asian markets.”
These ambitions, however, have yet to be realised. One front running project, Lake Way, went into receivership on the brink of production in October 2021, although it was subsequently rescued by Czech-owned Sev.en Global Investments last year. The other project, Beyondie, which did finally start to produce and sell SOP commercially in 2022, also entered administration in August.
In the US, meanwhile, Peak Minerals is developing the Sevier Playa SOP project in Millard County, Utah. This well-advanced project has the potential to become America’s largest SOP producer, targeting eventual production of 474,000 t/a under its second phase expansion plans (Fertilizer International 511, p44). In March, the company secured a $30 million loan from a strategic investor to fund front-end engineering and design (FEED) and preconstruction activities.
ICL has made a success in growing the market for polyhalite since converting its Boulby mine in the UK to production of this low-chloride multi-nutrient fertilizer, branded Polysulphate, five years ago. Boulby officially became the world’s only polyhalite producer in August 2018. Since then, Polysulphate production at the mine has continued to rise to meet demand – reaching 953,000 tonnes in 2022, up by 21 percent year-on-year. Revenues from ICL’s polyhalite product range also increased last year due to higher selling prices (Fertilizer International 514, p19).
TESSENDERLO KERLEY CELEBRATES 30 YEARS OF SOLUPOTASSE®
SoluPotasse® , Tessenderlo Kerley’s flagship SOP (sulphate of potash) fertilizer brand, is celebrating its 30th birthday in 2023. The market-leading product has been providing growers across the globe with the high quality, water-soluble grade of SOP for more than three decades.
A proud legacy
When SoluPotasse® was introduced into the market in 1993, Tessenderlo Kerley was the first SOP manufacturer worldwide to develop a fully soluble grade of SOP. The product was launched by the company in response to an increasing demand from growers wishing to use SOP in fertigation systems.
SoluPotasse® , which is produced in Belgium, has since become the global leading water-soluble SOP brand. Over three million tonnes have been sold since its launch, with sales in more than 100 countries. This makes ‘the pink bag’ (see photo) the world’s most-popular water-soluble SOP product.
SoluPotasse® is widely regarded as being best-in-class. It provides a highly soluble form of potassium and sulphur (in sulphate form) and is suitable for a wide variety of crops via fertigation.
This high-grade product, developed and subsequently enhanced by a team of scientists and agronomists, has set new standards. Its formulation ensures efficient nutrient uptake by plants and delivers superior results compared to traditional potassium fertilizers.
It continues to be valued by professional growers throughout the world as a versatile water-soluble fertilizer capable of boosting crop yields and quality. This is especially true for chloride-sensitive crops and areas at risk from salinity.
A sustainable SOP fertilizer
“SoluPotasse® has been recognised for many years as a leading product in sustainable agriculture. It contains virtually no chloride, which ensures that soil salinity can be avoided, and its superior soluble quality makes it ideal for fertigation and precision farming. Furthermore, SoluPotasse® has a carbon footprint across the full value chain that is 15-20 percent lower than the average for SOP production. We have dedicated considerable work and investments in our production processes over the last couple of years and our ambition is to decarbonise our production even more in the years to come,” explains Geert Gyselinck, Executive Vice President Tessenderlo Kerley International.
“By upcycling sulphur by-products from refineries into safe, non-hazardous fertilizers that become a valuable resource for growers, our SOP fertilizers are actively contributing to creating sustainable agriculture throughout the world. Moreover, the by-product hydrochloric acid from our SOP production process is, in turn, converted into coagulants that are used for the treatment of municipal and industrial wastewater, as well as for the purification of drinking water.”
A bright future
As SoluPotasse® celebrates its remarkable 30-year journey, Tessenderlo Kerley is as committed as ever to innovation and sustainable agriculture – and is continuing to collaborate globally with researchers and farmers on further advances in SOP fertilizers. The company is also exploring new technologies, refining its formulations, improving its production energy mix, and decarbonising its processes.
(SoluPotasseis a registered trademark of Tessenderlo Group.) ®
Geert Gyselinck says Tessenderlo Kerley will become an even more sustainable company in the next 30 years:
“We have an undisputed strategy to remain at the forefront of the specialty SOP market. To this end, we will continue to consistently deliver high-quality products while simultaneously improving our focus on customer service.
“As we celebrate the legacy of Solu-Potasse® , we must acknowledge its significant contribution to agricultural productivity and environmental preservation. Here’s to the 30 years of excellence realised so far and the many more years to come!”
In February, Anglo American also unveiled a strategy update for its large-scale Woodsmith polyhalite mine project in the UK. The mining major has earmarked around $4 billion to complete the under-construction project. Initial production of the company’s POLY4 polyhalite fertilizer is now scheduled to begin in 2027. The mine’s ultimate annual output has also been increased to 13 million tonnes (Fertilizer International 514, p44).
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