Want Higher Yield and Sugar Content? Why Orange Growers Choose Protassium+ SOP Fertilizer

Unwanted Side Effects

Citrus growers know that a profitable yield can only be achieved when enough potassium is supplied. But is your potassium fertilizer also delivering other elements that could harm your citrus trees and fruit quality?

Citrus trees are chloride-sensitive. According to SOPIB (Sulphate of Potash Information Board), chlorides absorbed in large amounts accumulate in the tree’s tissue, which negatively affects tree growth and fruit quality. With high salinity water found in many core citrus-growing areas, irrigation water often contributes to increased chloride levels in the soil. Unfortunately, your K source could be too.

Muriate of potash (MOP or KCl) is a common citrus tree fertilizer. While MOP’s high potassium content is beneficial, its high chloride content is not.

To avoid the harmful effects of chloride, choose Protassium+ premium sulfate of potash. It is a naturally produced fertilizer with less than 1% chloride content. (MOP’s chloride content is 47%.) Protassium+ SOP also contains:

  • 50% potassium
  • 17% sulfate sulfur

Sulfate sulfur is beneficial to citrus crops. Widely known as the fourth macronutrient, sulfur helps with overall tree health during crop growth, fruit initiation and development.

Higher Yield and Quality

By replacing MOP with sulfate of potash (SOP) in your citrus tree fertilizer, you may improve the yield and quality of your grove’s output. Published research comparing MOP with SOP in citrus crops have shown that SOP treatment results in:

  • Heavier fruit [1]
  • Higher juice content [1,2,3,4]
  • Lower citric acid content (sweeter fruit, higher juice quality) [2]
  • Higher sugar content (higher juice Total Soluble Solids/TSS) [1,4]

All of these attributes contribute to higher yield, better quality and increased profitability.

Protassium+ SOP For Your Grove

Avoid the chloride accumulation that can happen with MOP applications. To promote tree health and fruit quality, choose the right K for your groves. Choose Protassium+ premium sulfate of potash for your citrus tree fertilizer.

Protassium+ SOP is available in a wide variety of grades – granular, soluble powders, organic – to provide application options and flexibility in delivery timing. To find your local Protassium+ fertilizer retailer, contact your Compass Minerals rep.


[1] Ashraf, M.Y.; Hussain, F.; Ashraf, M.; Akhter, J.; Ebert, G. (2013) Modulation in yield and juice quality characteristics of citrus fruit from trees supplied with zinc and potassium foliarly. Journal of Plant Nutrition 36, 1996-2012.

[2] Ashraf, M.Y.; Gul, A.; Ashraf, M.; Hussain, F.; Ebert, G. (2010) Improvement in yield and quality of kinnow (Citrus deliciosa x Citrus nobilis) by potassium fertilization. Journal of Plant Nutrition 33, 1625-1637.

[3] Quaggio, J.A; Junior, D.M; Boaretto, R.M. (2011) Sources and rates of potassium for sweet orange production. Science Agriculture 68, 369-375.

[4] Shirgure, P. S., and Srivastava, A. (2013). Plant growth, leaf nutrient status, fruit yield and quality of Nagpur mandarin (Citrus reticulata Blanco) as influenced by potassium (K) fertigation with four potash fertilizer sources. Scientific Journal of Crop Science 2(3), 36-42.