💄 Potassium

• K containing minerals are primary minerals like feldspar/ or-thoclase, Muscovite and Biotite.
• Highest use of potassic fertilizer in the state of Maharashtra.
• Heavy application of potassium fertilizers often lead to reduced absorption of Zn & Cu.

a. KCL

• It is most common and cheap fertilizer among potassic fertilizers.
• It contains highest (60 % K₂O) among all potassic fertilizer.
• Also known as Muriate of Potash (MOP) /potassium chloride.
• This fertilizer is suitable for acidic and heavy soils but not for alkaline soils
• It shouldn’t be used in sugarcane, sugar beet, tobacco, tomato and potato because in sugar crops, accumulation of sugar is affected due to chloride ion present in the fertilizer.
• Higher content of chloride ion reduces burning quality of tobacco and interfere with starch content in Solanaceae crops.
• In these crops should be used K₂SO₄ and KNO₃ instead KCL.

b. K₂SO₄ (Potassium sulphate)

• Also known as Sulphate of Potash (SOP).
• Contains 48 % K₂O, 17.5 % S.
• Potassium sulphate is used where quality of crop is required because KCL reduce the quality of crops.
• Suitable for light soil and for those crops for which MOP is unsuitable.

c. KNO₃

• Potassium nitrate or salt petre or nitre
• It contains 46 % K₂O & 13% N
• It is an excellent source of potassium and nitrogen and mainly used for fruit trees, tobacco and vegetables.

Conversion

• % K₂O = K x 1.20
• % K = % K₂O x 0.83

Application

• The K fertilizers are usually applied before the crop is planted or sown, that is the basal dressing.
• Since the applied K is not lost from the soil either by leaching or by fixation, K fertilizers can be applied well in advance but it is preferable to apply only just before planting.
• Top dressing with K fertilizers can also be done for vegetables and other crop.