K1, K2, K3 = 113,150, 180 kg K2O/ha
Zhengzhou, China: exch. soil K: 87.7 mg/kg

Muriate of Potash 60 (MOP) ‘granular B ’

Muriate of potash (MOP):

• is an all-purpose potash fertiliser that is used in all chloride tolerant crops and on all soil types as a main source of the plant nutrient potassium.
• is usually applied on medium and heavy soils during autumn on stubbles or pre-drilling and is afterwards incorporated into the topsoil. Mainly on light soils a spring top dressing is recommended. On medium and heavy soils, it is also possible to carry out a rotational fertilisation to those crops with the largest K demand.

Use of Muriate of potash (MOP)

• MOP is a highly concentrated potash fertiliser. It is world wide the most important potash source suitable for all chloride tolerant crops.
• MOP ‘fine’ is also used for the processing of compound fertilisers.

Effect of MOP application on maize grain yield, gross income and VCR

MOP for larger yields, improved quality and higher income:

• Due to the multiple role that potash plays in the plant metabolism, e.g. photosynthesis, transport of assimilates, protein formation, enzyme activity and water balance, it promotes yield and quality of crops and prevents crops from biotic and abiotic stress.
• Hence adequate K application improves yield and quality as well as storability and shelf-life of crops.
• Due to its high K concentration, MOP is therefore in many situations the most cost effective K source.
• MOP is recommended as ideal potassium fertiliser to crops with high K requirement, such as most cereals, oil, sugar and fibre crops, which are tolerant to chloride or where, because of adequate rainfall, accumulation of chloride in the rooting zone does not occur.
• MOP is ideally suited to replenish depleted soils where long-term K omission has led to a decline in soil K availability.
• MOP is also suited for annual maintenance dressings to keep the soil K status in the adequate supply range.
• The yield promoting effect of MOP is often connected to an adequate supply of the other two macronutrients Mg and S, and hence MOP application is ideally combined with Kieserite dressings.
• Worldwide field observations have shown the positive effect of  balancing K supply through MOP with magnesium and sulphur by combining the MOP application with Kieserite.

Fertiliser recommendation

The application rate of MOP is adjusted based on:

• the K demand of the crop or crop rotation
• the soil K supply status and the K dynamics in the soil
• additional K sources (organic manure, irrigation water)
• soil texture and water dynamics of the soil

In annual crops, frequent soil analysis and in perennial crops, regular leaf analysis is important tools for adjusting the fertiliser application to crops requirement.

Timing and frequency of MOP application depends on:

• soil texture, and water dynamics; the lighter the soil and the more humid the climate, closer should be the application to the peak demand, the more often the application should be split.
• Autumn application in temperate climates is suitable for medium to heavy textured soils, improving K distribution in the whole rooting zone, reducing labour peaks in spring and avoiding damage through Cl during Cl sensitive stages of plant development.

Recommendations in the table below may serve as guidelines for soils with a medium K supply.