Sulphate of Potash for Quality... scan

Potassium fertilizer is commonly added to improve the yield and quality of plants growing in soils that are lacking an adequate supply of this essential nutrient. Most fertilizer K comes from ancient salt deposits located throughout the world.

The word “potash” is a general term that most frequently refers to potassium chloride (KCl), but it also applies to all other K-containing fertilizers, such as potassium sulfate (K2SO4), commonly referred to as sulfate of potash (or SOP).

I came across a nice pamphlet describing some of the advantages of using potassium sulfate as a source of potassium fertilizer.  It was written several years ago by the Potash Export Company in Vienna (Kali Export Gesellschaft).

Here is a link to the pdf of the booklet:

Sulfur, an overlooked nutrient…Are you keeping track?

Sulfur deficiency symptoms in corn

Since S deficiencies are increasing in many areas, the use of this nutrient is becoming more common. The most common forms of S used in fertilizer are elemental S and SO₄. Thiosulfate forms of S are also commonly available in many regions. A review of how S behaves in the soil is useful to get top crop performance.

Sulfur plays two important roles in agriculture…as an essential nutrient required for proteins and enzymes…and as a soil amendment for improving alkaline soils.

Many crops require between 10 to 25 lb/A of S each year. While this is not as much as some other nutrients, the frequency of crop S deficiency has been steadily increasing since many fertilizers do not routinely contain S and deposition of air-borne S has decreased. 

Although S exists in many different chemical forms in nature, plants primarily absorb it in the SO₄ form. The SO₄ molecule carries a negative charge, so it moves freely with soil moisture. As a result, SO₄ concentrations are sometimes greater with increasing depth in the soil below the rootzone. There are several excellent sources of plant-available SO₄ that will provide immediate crop nutrition. These include materials such as potassium-magnesium sulfate, ammonium sulfate, or potassium sulfate.

Elemental S is totally unavailable for plant uptake since it can not be directly taken up by roots. How­ever, when elemental S is added to soil, it gradually becomes converted (oxidized) to the plant-available SO₄ form. 

Large particles of sulfur will be slow to convert to sulfate

The transformation of elemental S to SO₄ is controlled by many factors. Since this conversion is done by soil microbes, several environmental and physical conditions govern how quickly this change takes place. In general, S oxidation takes place most rapidly in warm and moist soils. But field application should take place some time before the plants have a need for SO₄.

The physical properties of elemental S are also important. Small-sized particles have the most surface area and the most rapid reaction. However, fine particles of S can be difficult to apply. Fertilizer manufacturers have developed useful techniques where very fine S particles are clumped together with expandable clay to form a pellet which disintegrates in the soil.

Dr. Tim Hartz examines sulfur pastilles

Elemental S is highly acidifying after it is oxidized in the soil. It is commonly used to treat high-pH soils or to amend calcareous soils loaded with harmful concentrations of sodium. The specific S application rates should be calculated with the aid of a crop adviser.

Thiosulfate has also become a popular source of S nutrition for crops. Thiosulfate generally converts to SO₄ within a few weeks in typical summer growing conditions. Thiosulfate has also been shown to have beneficial effects on N transformations and may offer some unique benefits for plant metabolism.

Thiosulfate fertilizer

There is no reason to risk yield loss from S deficiencies. When the need for S is suspected, there are many excellent materials that are available to meet crop needs.

Sulfur burners are sometimes used to treat irrigation water with high concentrations of bicarbonate

Monoammonium phosphate (MAP): A great phosphate fertilizer

MAP : Monoammonium phosphate fertilizer

Monoammonium phosphate (MAP) is a widely used source of P and N. It is made of two constituents common in the fertilizer industry and has the highest P content of any common solid fertilizer.

Production

The process for manufacturing MAP is relatively simple. In a common method, a one to one ratio of ammonia (NH3) and phosphoric acid (H3PO4) is reacted and the resulting slurry of MAP is solidified in a granulator. The second method is to intro­duce the two starting materials in a pipe-cross reactor where the reaction generates heat to evaporate water and solidify MAP. Variations of these methods are also in use for MAP production. An advantage of producing MAP is that lower quality H3PO4 can be used compared with other P fertilizers that often require a more pure grade of acid. The P2O5 equivalent content of MAP varies from 48 to 61%, depending on the amount of impurity in the acid. The most common fertilizer composition is 11-52-0.

Chemical Properties

Chemical formula:        NH4H2PO4

P2O5 range:                   48 to 61%

N range:                       10 to 12%

Water solubility (20º)     370 g/L

Solution pH                   4 to 4.5

Monoammonium  fertilizer: one mole of ammonium and one more of phosphate

 Agricultural Use

MAP has been an important granular fertilizer for many years. It is water soluble and dissolves rapidly in soil if adequate moisture is present. Upon dissolution, the two basic components of the fertilizer separate again to release NH4+ and H2PO4-. Both of these nutrients are important to sustain healthy plant growth. The pH of the solution surrounding the granule is moder­ately acidic, making MAP an especially desirable fertilizer in neutral and high pH soils. Agronomic studies show that there is no significant difference in P nutrition from various commercial P fertilizers under most conditions.

Granular MAP is applied in concentrated bands beneath the soil surface in proximity of growing roots or in surface bands. It is also commonly applied by spreading across the field and mixing into the surface soil with tillage. In powdered form, it is an impor­tant component of suspension fertilizers. When MAP is made with especially pure H3PO4, it readily dissolves into a clear solution that can be used as a foliar spray or added to irrigation water. The P2O5 equivalent content of high-purity MAP is usually 61%. 

Management Practices

There are no special precautions associated with the use of MAP. The slight acidity associated with this fertilizer reduces the potential for NH3 loss to the air. MAP can be placed in close proximity to germinating seeds without concern for NH3 damage.

When MAP is used as a foliar spray or added to irrigation water, it should not be mixed with calcium or magnesium fertilizers. MAP has good storage and handling properties. Some of the chemical impurities (such as iron and aluminum) naturally serve as a conditioner to prevent caking. Highly pure MAP may have a conditioner added or may require special handling to prevent clumping and caking. As with all P fertilizers, appropriate management practices should be used to minimize any nutrient loss to surface or drainage water.

A high purity source of MAP is used as a feed ingredient for animals. The NH4+ is synthesized into protein and the H2PO4- is used in a variety of metabolic functions in animals.

Non Agricultural Uses

MAP is used in dry chemical fire extinguishers commonly found in offices, schools, and homes. The extinguisher spray dis­perses finely powdered MAP, which coats the fuel and rapidly smothers the flame. 

A pdf version of this post is available from the IPNI website here:

Abbreviations and notes: N = nitrogen; P = phosphorus; NH4⁺ = ammonium; H2PO4^- = phosphate. MAP is also known as ammonium phosphate monobasic, ammonium dihydrogen phosphate

Proper nutrition gives children a good start to a healthy life

IPNI recently released a book titled:

Fertilizing Crops to Improve Human Health: A Scientific Review

The authors explain how adequate plant nutrition can improve human health and promote a more prosperous and productive life.  More on this topic later, but the book can be downloaded for free from the IPNI website HERE

 This picture is part of a promotional series developed by the
Nutrients for Life Foundation a few years ago (nutrientsfor life.org)

Fertilizer helping all kinds of little sprouts to grow

Plant nutrients are in everything we eat

The link between plant nutrients and an abundant and healthy food supply is clear.  Of course appropriate management and careful stewardship is required, but the vital role of fertilizer remains unchanged.

This picture is part of a promotional series developed by the 

Nutrients for Life Foundation a few years ago (nutrientsfor life.org)

Thank mom for the pancakes and N P K for the ingredients

Plant nutrients are needed everywhere

This picture reminds me that plant nutrients are an essential part of almost every activity of our daily lives.   We can't grow food without the basic building blocks!  They are also an essential component of wood, fuel, clothes,...   

ipe starts with the same essential ingredien

This picture is part of a promotional series developed by the Nutrients for 

Life Foundation a few years ago (nutrientsfor life.org)