Improving the Nutritional Quality of Crops with Potassium

Globally, potash is one of the most highly respected and utilized fertilizers and is an extremely versatile source of potassium, one of the three primary macronutrients plants require. Along with nitrogen and phosphorus, potassium is essential for agricultural production with a unique role in improving the quality of crops worldwide, earning it the moniker of “The Quality Element”.

What is fascinating about potassium is the number of different quality characteristics it is linked to. Of course, the term ‘quality’ will mean different things for different crops. For some crops, the nutritional quality will be the most important, while for other crops it may be their taste, color, odor, or texture. Or it may be the quality and quantity of natural compounds that are beneficial to health, such as medicinal properties. However, when exploring how to improve the quality of crops, we find that sufficient potassium nutrition is a consistent factor in achieving the highest crop quality.

ICL Potash fertilizer contains 62% K₂O, the highest on the market

Key Quality Parameters

Extensive evidence widely supports the crucial role potassium has in improving many important crop quality parameters:

• In grain and oilseeds, potassium improves the nutritional value by increasing the content of protein and oil in cereals and oilseeds, respectively.
• In tubers, potassium increases starch content and tuber size.
• In cereals, potassium produces plumper grains and stronger straw.
• In fruits and vegetables, potassium increases the size, vitamin C, and sugar content while also improving flavor and color.
• In crops such as cotton and flax, potassium improves fiber quality.
• In addition to improving quality, potassium helps maintain quality during storage and transportation, thus extending shelf life.

Nutritional Value of Crops

The fiber and energy content of produce are two parameters widely used in assessing the value of foodstuffs in the human diet. In addition, protein and oil content are often used as a basis for procurement systems and thus can affect the financial value of the produce. This is where potassium is proven to be beneficial, improving these important quality characteristics.

But what is potassium’s role in the plant, and how does it alter the nutritional value of produce? Potassium is involved in cycling nutrients within the plant, i.e., the movement of nitrogen from the roots to the shoots and carbon from the shoots to the roots, fruits, and other storage organs. Potassium travels with nitrate in the xylem to the shoot. Experiments with nitrogen isotopes show how a low potassium supply restricts nitrogen transport, inhibiting protein formation. Plants take up more nitrogen and, importantly, convert the nitrogen more rapidly into protein when they have a good supply of potassium. ICL’s high-quality Potash is excellent for this, as it contains 62% K₂O which is the highest on the market, making it an ideal source of potassium for all chloride-tolerant crops and soils.

Experiments by the International Potash Institute (IPI) in India show how potassium application increases the oil content of sunflower, almost doubling the overall oil yield.

In papaya, in addition to the significant yield increase, potassium also improves a number of the fruit’s major quality parameters, including:

• an increase in pulp thickness, i.e., the edible part of papaya fruit
• an increase in the sweetness of the papaya (the Total Soluble Solids, TSS), one of the prime fruit quality parameters
• a decrease in the acidity of the fruit.

Potassium can also improve vitamin C content in produce. Vitamin C is perhaps one of the most popular and widely known vitamins among consumers. In many crops, including cucurbits, cauliflower, onion, banana, guava, and papaya, soil and foliar application of potassium increases the level of vitamin C in the produce. The results from a sweet pepper experiment at the Zhejiang Agricultural University in China clearly illustrate how increasing potassium application increases both the yield and vitamin C content.

There are plenty of other examples where potassium improves the nutritional quality of produce, such as

• In citrus, potassium increases the citric and ascorbic acid content of the juice and improves other juice characteristics, including the acid/sugar ratio and soluble solids content.
• The fruit of tomato plants with proper potassium nutrition contain more total solids, sugars, acids, carotene, and lycopene.
• In maize, potassium application increases the protein content, as shown in the results from another IPI experiment in India (below). In this case, the proportion of protein nitrogen to non-protein nitrogen also increased, producing more digestible dry matter and protein in the maize silage, improving the feed value of forage for livestock.

Processing Quality

For grains destined for processing, potassium improves the synthesis of gluten and prolamine and the formation of proteins responsible for improving baking quality. Research has also demonstrated that potassium increases the starch content of rice, wheat, maize, soybean, sesame, and some forage crops. Meanwhile, with sesame, soybean, oilseed rape, groundnut, and cotton seeds, it is the oil content that improves with adequate potassium fertilization. For those growing cotton for fiber, potassium increases boll size, improves micronaire value, fiber strength, and fiber length, and increases the percentage of mature fibers.

Potassium improves the processing quality of potatoes; insufficient potassium reduces photosynthesis, decreasing tuber dry matter and lowering starch production. Potassium deficiency also causes the accumulation of reducing sugars, producing undesirable, dark-colored chips. In addition, internal blackening of potato tubers may be related to potassium deficiency, while evidence suggests that adequate potassium application can reduce bruising and hollow heart.

In sugar beet grown with high nitrogen and inadequate potassium, the sugar content is lower, and there is a higher amino nitrogen content that reduces the extractability of sugar from the beet. But with adequate potassium, the sugar beet root yield is higher, with increased sugar content and, consequently, a much greater sugar yield.

The natural evaporation production process at ICL’s Dead Sea production site means our high-quality potash fertilizers have a significantly lower carbon footprint than alternative products.

Potassium in Plants

So, how does potassium achieve these impressive benefits? Potassium has two vital roles in plants. First, it is essential for the activation of enzymes fundamental to metabolic processes, especially the production of proteins and sugars. Second, potassium maintains the water content and thus rigidity, or turgor, of the plant cells, creating the perfect environment for photosynthesis and, ultimately, the production of sugars that end up in the fruits, grains, roots, and tubers.

Choosing Potassium for Quality Produce

While the amount of potassium required for optimum yield is also often sufficient to produce good quality produce, sometimes the need to enhance quality may be more important than other aspects of yield production. This is especially true when higher produce quality secures the best economic return. Bananas, cotton, potatoes, tobacco, turf grasses, and ornamentals are all great examples where potassium application needs to be optimized for quality as well as yield.

When you consider the number of crops where potassium improves the nutritional quality of produce, be it the protein, oil, sugars, or other nutritional characteristic, it is easy to understand why potassium is known as the quality element.

ICL’s professional agronomic and technical teams are on hand to provide our customers with advice and support to ensure optimum potassium nutrition.

Sources of Potassium

Explore the extensive collection of high-quality potassium fertilizers in ICL’s portfolio of plant nutrition products to find the perfect product to suit every crop and growing condition. As one of the world’s leading manufacturers of potash fertilizers, ICL creates high-quality potash fertilizers that are superb sources of potassium to increase yield and improve crop quality.