Potassium nitrate: A dual solution - SQM Specialty Plant Nutrition


Potassium nitrate: A dual solution

Potassium (K) is an essential nutrient for potato crops, as it affects various aspects of yield and quality throughout the growth period. There are three main potassium fertiliser sources namely potassium nitrate (KNO3), potassium sulphate (K2SO4) and potassium chloride (KCl). The major difference between these potassium sources is the counter-ion that comes with the potassium nutrient. KNO3 contains 38% potassium and 13% nitrate nitrogen (N-NO3-). Both potassium and nitrogen (N) are used in large quantities for potato production.

Potassium sulphate contains 40% potassium and 18% sulphur (S). Potassium is needed in large amounts. Sulphur, although important in plant nutrition, is needed in much lower quantities and excess application can create unwanted salinity in the root zone. Potassium chloride contains 50% potassium and chloride (Cl-). It is a common fertiliser and provides only potassium as a nutrient and no additional N or S.

Work smart

Potatoes are among several high-value crops that are particularly sensitive to Cl and salt. Continued application of potassium sources with a high Cl content or salt index can have a toxic effect, building up in the soil and contributing to lower yields, lower quality and lost income.

When producers replace KNO3 with K2SO4 and KCl in their fertiliser recommendation programme, an extra 13% N must be applied to compensate for the N they lose when not applying KNO3 (Table 1).

Bester and Maree (1990) conducted a two-year trial to compare the number and weight of tubers between KNO3, K2SO4, and KCl potassium treatments. They found that the application of KNO3 significantly increased the number and weight of tubers compared to K2SO4 and KCl.

Higher yield with KNO3

SQM is a global market leader in producing KNO3 of natural origin. Their product is chlorine-free, 100% water-soluble, and has the lowest carbon footprint, providing the producer with high-quality KNO3 products such as Ultrasol® K Plus**, Ultrasol®ine K Plus*** and Qrop® K****.

Ultrasol® K Plus is a crystalline water-soluble KNO3 source for producing outstanding crops. The additional N-NO3- ensures rapid absorption by the plant. It has very low levels of Cl, sodium, and heavy metals. It is a free-flowing, fine crystalline powder that dissolves quickly in water. It can be mixed with all water-soluble fertilisers, and it is also compatible with most pesticides in foliar application. N-NO3- is non-volatile and enhances the uptake of other cations (K+, Ca2+, Mg2+). Due

to its low N/K ratio, Ultrasol® K Plus is suitable for all crops and growth stages, including flowering and ripening stages. Ultrasol®ine K Plus is SQM’s brand of crystalline water-soluble KNO3 that contains the plant nutrient, iodine. Ultrasol®ine makes it easy for producers to ensure the right amount of iodine in the nutrient solution and prevents excess uptake in leaves or fruits. Iodine is a structural component of plant proteins.

A versatile product

Qrop® K**** is a prilled KNO3 source that is rapidly absorbed by the plant and provides N-NO3-, the plants’ preferred N source.

This product can be mixed with virtually any straight fertiliser applied in agriculture. Due to the elements  it provides and its low salinity, 

Qrop® K can be applied to a wide range of crops and during each growth stage. More than 80% of the N consumed by plants is nitrate, the preferred nitrogen source of plants. Using KNO3, producers can maximise the application of potassium and nitrate that cannot be obtained by using either KCL or K2SO4. Therefore, with Ultrasol K Plus, the potato is being supplied with two of its main nutritional elements in one product.

Table 1: Potassium fertilisers with their nutrient content


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** Reg No K5020 (Act 36 of 1947). Registration holder: Sociedad Quimica y Minera (Africa) (Pty) Ltd.

***  Reg No K11316 (Act 36 of 1947). Registration holder: Sociedad Quimica y Minera (Africa) (Pty) Ltd.

**** Reg No K5021 (Act 36 of 1947). Registration holder: Sociedad Quimica y Minera (Africa) (Pty) Ltd.


The information herein contained is given to the best of SQM’s knowledge and is believed to be accurate. The conditions of your use and application of the suggested recommendations are beyond our control. No warranty

is made as to the accuracy of any data or statements contained herein. SQM specifically disclaims any responsibility or liability relating to the use of the recommendations and shall under no circumstances whatsoever, be liable for any special, incidental or consequential damages arising from such use.

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