Tuesday, July 1, 2014

Kieserite... naturally occurring magnesium sulfate

Kieserite is a naturally occurring mineral that is chemically known as magnesium sulfate monohydrate (MgSO4·H2O). It is mined from geologic marine deposits and provides a soluble source of both Mg and S for plant nutrition.
Magnesium deficient grapes


Kieserite is primarily obtained from deep underground deposits of minerals in Germany. It is present in the remnants of ancient oceans that were evaporated and are now buried beneath the earth’s surface.
Mining in Germany
These mineral resources contain a variety of valuable plant nutrients. The ore is brought to the surface where the magnesium salts are separated from potassium and sodium salts using a unique, dry electrostatic (ESTA) process.

The fine crystalline kieserite is sold for direct application to soil, or it is granulated to a larger particle size that is better suited for mechanical fertilizer spreading or for bulk blending with other fertilizers.

Chemical Properties

Chemical formula:   MgSO4·H2O
Mg content:             16% (kieserite fine); 15% (kieserite granular)
S content:                22% (kieserite fine); 20% (kieserite granular)
Solubility:                 417 g/L (20°C)
Solution pH:             9
Granular kieserite

Agricultural Use

Kieserite provides a highly concentrated form of two essential plant nutrients—Mg and S. Since kieserite applications have no major effect on soil pH, it can be supplied to all kinds of soil, irrespective of soil pH. It is commonly used prior to or during the growing season to meet the nutrient require­ment of crops. Due to its high solubility it can be used to supply both Mg and S during peak periods of crop demand. Since kieserite is an earth mineral mined from naturally occurring deposits, it is permitted as an organic nutrient source by some organic certi­fying agencies.

Kieserite itself is not used as foliar fertilizer or in fertigation systems, but it serves as raw material for the production of Epsom salt (MgSO4·7 H2O), which is totally soluble and suitable for both fertigation and foliar application.
Fine kieserite particles

 Management Practices

Many soils are low in Mg and require supplemental nutrients to support crop yield and quality. Sandy-textured soils and soils with a low pH (such as highly weathered tropical soils) are frequently characterized by a low Mg supply for plants. Under these conditions, it is a prerequisite to raise the Mg content in the soil by adequate fertilization.

Splitting Mg applications into two or more doses is recommended in areas with high precipitation in order to avoid leaching loss­es. Soils in temperate climates with higher clay content may have higher Mg contents and are often less prone to leaching losses.

Fertilizer Mg application rates vary depending on factors such as the specific crop requirement, the quantity removed during harvest, and the ability of soil minerals to release adequate Mg in a timely manner to support crop yield and quality. Kieserite application rates are typically in the range of 200 to 300 kg/ha for many crops. Additional Mg and S demands during peak growth periods demand can be met by foliar application of materials such as Epsom salt or a variety of soluble nutrient sources.
Magnesium deficient soybeans

This post originally appeared as one in a series on specific nutrient sources on the IPNI website.

Thursday, June 12, 2014

Nutrient Deficiency Symptoms... Don't wait until you see them

 Plant nutrient deficiency symptoms begin to appear when one of the essential nutrients is lacking.
Iron-deficient cowpeas
Some­times deficiencies appear early in the growing season when soils are cold or wet, and when root activity is low. Deficien­cies are also commonly observed later in the season when the soil cannot satisfy the high nutrient demand of a rapidly growing crop. Whether the deficiency is caused by poor root uptake or low nutrient-supplying power of the soil, proper management practices can help alleviate these problems.

Deficient plants do not initially show any obvious symptoms of nutrient shortage other than slower growth, which can also be due to many factors. In the case of a mild deficiency, plants may never show a visual symptom ex­cept slow growth and reduced yield.

Nutrient deficiency causes a disruption in any number of essential metabolic processes within the plant. Crops mature unevenly because deficiencies rarely occur uniformly across entire fields. This leads to lower yield, harvest­ing difficulties and poorer crop quality. And as previously stated, this can all occur without diagnostic symptoms appearing.
Potassium-deficient cucumber

When deficiency symptoms become noticeable, severe stress is already occurring and steps should be considered to overcome the problem, if it is practical and economical to do. The effects of other stresses such as drought and pests can complicate diagnoses. Another problem is that not all deficiencies produce clear-cut symptoms. Then there is the possibility of multiple deficiencies. The most severe deficiency may be manifested first. Knowing which nutrients are mobile or immobile within the plant is helpful in pinpointing the cause of the deficiency symptom. Diagnosing symptoms also requires understanding of specific crop colors and markers. It is worth noting that some crops are more susceptible to visible symptoms than others.

Plant analysis (tissue testing) is useful for diagnosing specific nutrient deficiencies as they arise. It is best when nutrient concentrations in deficient plants growing in problem areas are compared with healthy plants to identify the differences. It is also helpful to collect soil samples for analysis from the two areas at the time the plant samples are col­lected.
Zinc-deficient potato
Tissue testing also is valuable for monitoring plant health during the season to verify that nutrient concentrations do not drop below nor exceed established critical values. Guidelines have been developed for many crops for what the ap­propriate nutrient concentrations should be during various growth stages. Supplemental fertilization should be considered if the concentrations fall below these established thresholds.

Pre-season soil testing should also be part of a strategy for preventing nutrient shortages. In addition to helping avoid plant stress, soil analysis will allow decisions to be made that will avoid over or under application of fertilizer and resulting economic inefficiency.

The International Plant Nutrition Institute (IPNI) has a large database of nutrient deficiency images that is continually growing. Visit the website at: http://media.ipni.net. Additionally, a collection of over 500 of our best plant nutrient deficiency photos is available for purchase at http://ipni.info/nutrientimagecollection. A condensed version of this collection is available as an app for iPhones and iPads at http://www.ipni.net/article/IPNI-3273. When nutrient deficiency symptoms appear, first act quickly to diagnose the problem and then make plans to correct it and to avoid having them reoccur in the future.  
Potassium-deficient cotton
This blog posting originally appeared as part of the Plant Nutrition Institute quarterly newsletters "Plant Nutrition Today".  The entire series can be viewed here.

Tuesday, June 3, 2014

Using potash fertilizer to kill zebra mussels in Lake Winnipeg

An interesting project is currently underway in Lake Winnipeg. 
Lake Winnipeg in Manitoba, Canada
The Manitoba government is trying to stop the growth of the aggressive zebra mussel.  Zebra mussels, native to Eastern Europe and Western Asia, are extremely invasive and latch onto boats, buoys, rocks, and other structures.  

Zebra mussels are very difficult to control and previous attempts to halt their spread in the U.S. and Canada have largely been ineffective.  However mussels are sensitive to high potassium concentrations and it is hoped that this may be the key to slowing down their invasion.
Zebra mussels (Wikipedia)
A concentrated potassium chloride solution was recently added to the Winnipeg Beach Harbor and all of the zebra mussels were killed within ten days.  Potassium chloride does not have a negative impact on fish, other mussels, humans, or water quality as it gradually dissipates into the lake.
Zebra mussels (Wikipedia)
You will recall that Canada has the largest geologic reserves of potassium chloride in the world.  These mines harvest naturally occurring potassium minerals from the ground, wash away any impurities, and then sell valuable potassium fertilizer (potash) to agricultural regions around the world where soil reserves of potassium are too low to support healthy plant growth.  
Potash mine in Saskatchewan, Canada

You can read more about this in these news outlets:


Wednesday, May 14, 2014

So Many Choices - Selecting the Right Nutrient Source

The 4R principles of nutrient stewardship involve selecting the “Right Source” of nutrients to meet plant demands. This fundamental decision of nutrient source influences the process of choosing the Right Place, Right Time, and Right Rate for each field.

4R: Right Source, Right Rate, Right Time & Right Place

 A misconception persists that using manufactured fertilizers means opposing the use of organic nutrient sources. Most agronomists agree that selecting the right source of nutrients begins with first considering the supply of on-farm nutrients and then supplementing them with commercial fertilizers.

Integrated Plant Nutrient Management is the term used by agronomists to describe the appropriate use of both fertilizer and organic sources of nutrients. Every farming operation will differ in its access to various nutrient sources and there is a range in specific crop requirements, but all farmers have the goal of maximum crop output and harvest quality from the right nutrient application.

Organic nutrient sources can include soil organic matter, a small portion of which decomposes and releases nutrients each year. Crop residues vary greatly in nutrient content, but can be a contributing nutrient source in many situations. Animal manures are commonly used as a valuable source of plant nutrients. Manures and composts can have a wide range in nutrient
Compost can be a useful nutrient source
composition, so it is useful to have them chemically analyzed to assess their fertilizer-replacement value. Cover crops can also be a useful nutrient source. Legume cover crops have the benefit of providing extra nutrients by hosting N-fixing bacteria. Grass cover crops can capture and retain nutrients that might have otherwise leached past the root zone, then release their nutrients again as they decompose.

Many excellent commercial fertilizers can be used to deliver nutrients that are lacking for successful crop production. Commercial fertilizers are most commonly used as bulk blends of popular granular fertilizers; compound fertilizers, which are a mixture of multiple nutrients within a single fertilizer particle;  fluid fertilizers, homogeneous clear liquids which can be blended with materials such as micronutrients, herbicides, and pesticides, or diluted for foliar application; and suspension fertilizers which use a suspending clay or gelling agent to keep small fertilizer particles from settling out of the liquid.
Bulk blends

Fluid fertilizers

Additional considerations in selecting the Right Nutrient Source might include:

   The soil chemical and physical properties (such as avoiding nitrate application in flooded soil, or surface application of urea on high pH soils).

Preparing soil for rice
   Availability of fertilizer application equipment to get the nutrients delivered properly.

   Blends of multiple fertilizer materials must account for their chemical properties and compatibilities.

   Recognize sensitivities and secondary benefits of specific fertilizer materials (such as chloride additions that may be beneficial for small grains, but possibly detrimental for the yield and quality of other crops in excessive concentrations).

Selecting the Right Source of nutrients is too often overlooked due to tradition and the ease of doing the same thing every year. Remember that crop production is very complex and that successful farmers need to be both
artists and scientists with an understanding of all the 4R’s to meet their goals.

This post originally appeared as part of a series of quarterly newsletters (Plant Nutrition Today) published by the International Plant Nutrition Institute.

Wednesday, May 7, 2014

Potassium Sulfate - A potash fertilizer with many benefits

Soluble potassium sulfate
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).
Chemical formula; K2SO4

Potassium sulfate, Great Salt Lake, Utah

Potassium is a relatively abundant element in the Earth’s crust and production of potash fertilizer occurs in every inhabited continent. However, K2SO4 is rarely found in a pure form in nature. Instead it is naturally mixed with salts containing Mg, Na, and Cl. These minerals require additional processing to separate their components. Historically, K2SO4 was made by react­ing KCl with sulfuric acid. However, it was later discovered that a number of earth minerals could be manipulated to produce K2SO4 and this is now the most common method of production. For example, natural K-containing minerals (such as kainite and schoenite) are mined and carefully rinsed with water and salt solutions to remove byproducts and produce  K2SO4.  A simi­lar process is used to harvest  K2SO4 from the Great Salt Lake in Utah, and from underground mineral deposits.

In New Mexico (USA), K2SO4 is separated from langbeinite minerals by reacting it with a solution of KCl, which removes the byproducts (such as Mg) and leaves   K2SO4.   Similar processing techniques are used in many parts of the world, depending on the raw materials accessible.
Potassium sulfate

Chemical Properties
Chemical Formula:  K2SO4
K content: 40 to 44% (48 to 53% K2O)
S content: 17 to 18%
Solubility (25 ºC) 120 g/L
Solution pH approx. 7

 Agricultural Use
Concentrations of K in soil are often too low to support healthy plant growth. Potassium is needed to complete many es­sential functions in plants, such as activating enzyme reactions, synthesizing proteins, forming starch and sugars, and regulating water flow in cells and leaves.
Potassium-deficient cotton

Potassium sulfate is an excellent source of nutrition for plants. The K portion of the  K2SO4 is no different than other com­mon potash fertilizers. However, it also supplies a valuable source of S, which is sometimes deficient for plant growth. Sulfur is required for protein synthesis and enzyme function. There are certain soils and crops where the addition of Cl- should be avoided. In these cases, K2SO4 makes a very suitable K source. Potassium sulfate is only one-third as soluble as KCl, so it is not as commonly dissolved for addition through irrigation water unless there is a need for additional S.
Potassium-deficient almonds

Several particle sizes are commonly available. Fine particles (<0.015 mm) are used for making solutions for irrigation or foliar sprays since it is more rapid to dissolve. Foliar sprays of  K2SO4 are a convenient way to apply additional K and S to plants, supplementing the nutrients taken up from the soil. Leaf damage can occur if the concentration is too high.

Management Practices
K2SO4 is frequently used for crops where additional Cl- from more common KCl fertilizer is undesirable. The partial salt index of  K2SO4 is lower than some other common K fertilizers, so less total salinity is added per unit of K. The salt measurement (EC) from a  K2SO solution is less than a third of a similar concentration of a KCl solution (10 mmol/L). Where high rates of K2SO4 are needed, it is generally recommended to divide the application into multiple doses. This helps avoid surplus K accumulation by the plant and also minimizes any potential salt damage.

Potassium-deficient soybeans

A pdf version of this information is available
at the IPNI website here

Wednesday, December 18, 2013

Potassium chloride - the most common potash fertilizer (muriate of potash)

Potassium fertilizers are commonly used to overcome plant deficiencies.
Potassium deficient lettuce
 Where soils cannot supply the amount of K required by crops, it is necessary to supplement this essential plant nutrient. Potash is a general term used to describe a variety of K-containing fertilizers used in agriculture. Potassium chloride (KCl), the most commonly used source, is also frequently referred to as muriate of potash or MOP (muriate is the old name for any chloride-containing salt). Potassium is always present in minerals as a single-charged cation (K

Deeply buried potash deposits are found throughout the world. The dominant mineral is sylvite (KCl) mixed with halite (sodium chloride), which forms a mixed mineral called sylvinite. Most K minerals are harvested from ancient marine deposits deep beneath the Earth’s surface.
Mining potassium salts in Belarus
They are then transported to a processing facility where the ore is crushed and the K salts are separated from the sodium salts. The color of KCl can vary from red to white, depending on the source of the sylvinite ore. The reddish tint comes from trace amounts of iron oxide. There are no agronomic differences between the red and white forms of KCI.
Potassium fertilizer comes in several colors, depending on their geological source
Some KCl is produced by injecting hot water deep into the ground to dissolve the soluble sylvinite min­eral and then pumping the brine back to the surface where the water is evaporated. Solar evaporation is used to recover valuable potash salts from brine wa­ter in the Dead Sea and the Great Salt Lake (Utah).
Salt beds at the Dead Sea


                        Chemical Properties
                       Property:                            KCl
                     Fertilizer analysis             0-0-60
                     K content approx              50%
                     Water solubility (20o C)   344 g/L
                     Solution pH                      approx. 7

Agricultural Use
Potassium chloride is the most widely used K fertilizer due to its relatively low cost and because it includes more K than most other sources...50 to 52% K (60 to 63% K2O) and 45 to 47% Cl-.

Over 90% of global potash production is used for plant nutrition. Potassium chloride is often spread onto the soil surface prior to tillage and planting. It may also be applied in a concentrated band near the seed. Since dissolving fertilizer will increase the soluble salt concentration, banded KCl is placed to the side of the seed to avoid damaging the germinating plant.
Potassium fertilizer (KMg-SO4)

Potassium chloride rapidly dissolves in soil water. The K+ will be retained on the negatively charged cation exchange sites of clay and organic matter. The Cl- portion will readily move with the water. An especially pure grade of KCl can be dissolved for fluid fertilizers or applied through irrigation systems.
Management Practices
Potassium chloride is primarily used as a source of K nutrition. However, there are regions where plants respond favorably to application of Cl-. Potassium chlo­ride is usually the preferred material to meet this need. There are no significant impacts on water or air associated with normal application rates of KCl. Elevated salt concentrations surrounding the dissolving fertilizer may be the most impor­tant factor to consider.
Red potassium chloride

Non-agricultural Use
Potassium is essential for human and animal health. It must be regularly ingested because the body does not store it. Potassium chloride can be used as a salt substitute for individuals on a restricted salt (sodium chloride) diet. It is used as a deicing agent and has a fertilizing value after the ice melts. It is also used in water softeners to replace calcium in water.