Muriate of potash (KCl), Sulphate of potash (K2SO4) or NPK?
KCl and K2SO4 are sources of K used in agriculture. However, the fear of contributing to soil acidity after long period of use is a concern to the soil health and general well being.
Is there any current source of K fertilisers that one can use that does not acidify the soil,,other than the three listed above?
Dear Peter, you may use biosynthesized nano-K as K fertilizers which does not promote any soil acidity.
Agree with J. C. Tarafdar that K fertilizers are not acid generating. Soil acidity and too much alkalinity are big issues. Ammoniated sources of nitrogen is the chief cause of soil acidity. You may want to have your soil tested for adjusting for most crop plants the liming acid soil to 5.7 to 6.7 using limestone is a wonderful for improving the soil quality and crop productivity. If a maize crop was using significant amount of ammoniated nitrogen this should be counteracted by lime addition. In many areas the soils are alkaline and liming would be counter productive in those areas. In areas of over 7.7 pH the use of sulfur and ammoniated fertilizer can aid in developing more optimized soil crop environment. In terms of improving soils for reactions the use of organic amendments can help a broad spectrum of soil conditions. Crop wastes and manures are ideal for composing and addition to cropping areas.
While the reaction of K in the soil leads to an increase of the pH, Cl and SO4 have an acidifying effect.
From a product point of view MOP (KCl) is slightly acidifying, i.e., 100 kg of MOP 60 should be balanced by approximately 9 kg of aglime (CaCO3); however, in practice the Cl usually is leached out with rainwater and thus doesn't play a role, so over time MOP has a neutral-alkaline soil reaction.
(Note: Cl is worsening specific issues of saline/sodic soils and might have to be avoided).
Also SOP (KSO4) is a very balanced fertiliser: 100 kg of SOP should be balanced with approximately 10 kg aglime.
Provided both fertilisers are used within a balanced fertiliser program and applied to meet the crop requirement (for K and S) both may be addressed as "neutral" not promoting soil acidity.
As such mop or sop doesn't add to soil acidity, if at all it is being buffered.
Secondly, many mineral fertilizer components are coming to the market like Polyhalite Poly4, carrying ca,mg,k and s can be used for k with other secondary nutrition for soil and crop benefits.
The insufficiencies of Magnesium and Sulfur would motivate the use of Potassium Magnesium Sulfate. Brassicas are heavy uses of sulfur and soil mustards will often respond to sulfur in increasing both yield and quality. Where much coal is combusted for electrical generation sulfur can be provided for acid rainfall containing sulfates. The deficiencies in Magnesium can be widespread since potassium is often applied in lieu of magnesium. Where magnesium is deficient and soils are acid liming with dolomitic limestone is called for. The application of potassium without magnesium can promote deficiency in magnesium. Deficiency in magnesium plants give chlorosis and in animals it results in muscular tremors and heart issues. The application of potassium is motivated by the increase in yield and sugar contents of vegetables and fruits. In crops such as maize the soil reading of 100 ppm magnesium will be sufficient but if the reading is lower efforts will be needed to supply magnesium as well as potassium. When magnesium chlorosis is noted the use of foliar fertilization with magnesium salts can be effective.
Thanks a lot Paul for the informative piece. Indeed, the deficiencies and their influences on the availability of other nutrients is one area that needs more attention going forward.
Potassium is normally retained by plants tissues. Therefore good fertilizer sources for K are/could be: straw/crop stubble and wood ashes.
Also sheep wool contains potassium thus after harvesting the wool, the water where this was washed was used to replenish K in cultivated soils.
K deficiency draws attention for either of the K fertilizer. Monotonous application results those secondary effects including soil pH.
We must think now Polyhalite types for multiple nutrients and plant nutrition in balanced from.
This will avert soil conditions including pH.
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