Friday, February 18, 2011

Adding fertilizer to streams! What's next?

We usually think about keeping nutrients out of streams and lakes,because it stimulates too much biological activity.
This article appeared this week in the Vancouver Sun (British Columbia) newspaper.  Biologists are adding nitrogen and phosphorus fertilizer to streams to enhance aquatic productivity. This practice is not uncommon in the Pacific Northwest, but not recommended for most conditions.

Fertilizer in streams holds promise in rebuilding salmon stocks

VANCOUVER — Young steelhead and salmon showed a dramatic growth in streams seeded with sacks of slow-release fertilizer, a method that shows real promise to help rebuild collapsed salmon and steelhead spawning populations, according to B.C. biologists.

The method has proven effective at improving steelhead growth and survival in Vancouver Island streams in programs dating back to 1989.

Steelhead fry in treated areas are typically about 95 per cent larger than those in untreated streams, while coho fry are about 40 per cent bigger. Fish counts in the Keogh River found a 50 per cent increase in the number of coho that survived the freshwater stage of life.

Fisheries biologists are using fertilizers to replace the nutrients that would be added to the stream naturally by the rotting carcasses of fish that die after spawning, said Kevin Pellett of the B.C. Conservation Foundation. Enhancement programs are operating in 15 watersheds and 28 rivers on Vancouver Island and southwestern B.C.

The fertilizers are designed to stimulate growth of certain algaes that in turn cause the populations of insects such as mayfly and stonefly to thrive. Juvenile salmon and steelhead fry feed on those insects.

Steelhead fry growing downstream from the fertilizer caches are bigger and typically 75 to 250 per cent heavier than those upstream, which would not be expected to benefit from the improved food supply, according to the most recent data. Larger more robust fish are more likely to survive and return as spawning adults.

"We've switched to a new product called Crystal Green," he said.

Crystal Green is a slow-release agricultural fertilizer comprised of nitrogen and phosphate recovered from municipal waste water using a technology invented by civil engineers at the University of British Columbia. The Vancouver-based manufacturer, Ostara, is harvesting a waste material called struvite for the fertilizer from the sewage stream in suburban Portland, Oregon.

More about about struvite and Ostara in a later post.

Wednesday, February 16, 2011

Polyphosphate fertilizer... fluid phosphate basics

Polyphosphate fluid fertilizer

Phosphorus deficiency limits the growth and productivity of plants in many parts of the world. Since many soils are low in P, this nutrient is commonly added to improve crop yield and quality. Phosphorus is derived from geologic deposits distributed across the globe. 

Polyphosphate is an excellent liquid fertilizer that is widely used in agriculture.

Phosphoric acid is the starting material for most commercial phosphate fertilizers. However, the acidity and some of the chemi­cal properties make this material difficult to use directly. When phosphoric acid and ammonia are reacted, water is driven off and individual phosphate molecules begin to link together to form a “polyphosphate” fluid fertilizer.

A single phosphate molecule is called orthophosphate. “Poly” refers to multiple phosphate molecules linked in a chain. Each linkage of phosphate molecules has a name depending on its length, although polyphosphate is the general term that includes all of these linked molecules.

The most common ammonium polyphosphate fertilizers have N-P2O5-K2O composition of 10-34-0 or 11-37-0. Polyphosphate fertilizers offer the advantage of a high nutrient content in a clear, crystal-free fluid that is stable under a wide temperature range and has a long storage life. A variety of other nutrients mix well with polyphosphate fertilizers, making them an excellent carrier for micronutrients that may be needed by plants.
"Poly" in polyphosphate refers to chains of phosphate... short or long

Chemical Properties


Agricultural Use
In polyphosphate fertilizer, between half and three-quarters of the P is present in chained polymers. The remaining P (orthophosphate) is immediately available for plant uptake. The polymer phosphate chains are primarily broken down to the simple phosphate molecules by enzymes produced by soil microorganisms and plant roots. Some of the polyphosphate will decompose without the enzymes. The enzyme activity is faster in moist, warm soils. Typically, half of the polyphosphate compounds are converted to orthophosphate within a week or two. Under cool and dry conditions, the conversion may take longer.

Since polyphosphate fertilizers contain a combination of both orthophosphate and polyphosphate, plants are able to use this fertilizer source very effectively. Most P-containing fluid fertilizers have ammonium polyphosphate in them. Fluid fertilizers are commonly used in production agriculture, but not widely used by homeowners. Fluids are convenient for farmers since they can be easily blended with many other nutrients and chemicals and each drop of fluid is exactly the same. For most situations, the decision to use dry or fluid fertilizers is based on the price of nutrients, fertilizer-handling preferences, and field practices rather than significant agronomic differences.

Management Practices
Ammonium polyphosphate is primarily used as a source of P nutrition for plants. Since P has limited mobility in most soils, efforts should be made to place the material as close to developing roots as practical. Practices should be adopted to minimize the movement of P from the soil into adjacent water. Excess P in surface water can stimulate the growth of undesirable algae.

Non-agricultural Use
Phosphate is an essential component in human nutrition. Polyphosphate is an approved additive for food and requires no special precautions in handling. Polyphosphate compounds are widely used as a flame retardant on many products, including wood, paper, fabric, and plastic. It is also used as a commercial retardant for forest fires. The mode of action involves the ammonium polyphosphate forming a charred layer after burning, thereby preventing further flames.

Read the fact sheet on some of the important properties of polyphosphate and how it is used.

Where does phosphate fertilizer come from?

 Massive machines are used to recover phosphate rock from Florida
Maintenance of an adequate phosphate supply in the soil is essential for sustaining global food supplies. Many soils need an additional source of phosphate to supplement the native supply in order to meet this minimum requirement. Crops remove relatively large amounts of phosphate from the soil in the harvested portion. At some point, it is necessary to replenish the supply of this nutrient.

Early sources of P were limited to animal manure, which did not supply any new nutrients, but merely allowed them to be transported from one area to another. The first commercial fertilizer became available when it was discovered that adding acid to animal bones would chemically unlock the phosphate and make it available for plant uptake.
Early advertisement for superphosphate

Phosphate rock is the raw material now used in commercial fertilizer production. Phosphate rock is extracted from the earth in many countries. Most of the phosphate rock is used for fertilizer production, with smaller amounts going to various industrial uses. Although phosphate rock is a limited natural resource, at current rates of use the world phosphate rock reserves and resources should be adequate for the foreseeable future.
 Phosphate rock is generally extracted with surface mining techniques and then the pit is later filled, re-vegetated, and reclaimed. The quality of the rock will vary depending in the level of naturally occurring impurities. The rock is screened and crushed to prepare it for processing with a source of acid. After the phosphate rock has reacted with acid, the soluble phosphate is transformed into many common fertilizers and transported across the world. The largest users of phosphate fertilizers are China and India.

Phosphate has many important functions in plants. Perhaps the most noted roles are in photosynthesis, respiration, energy storage and transfer, cell division, and cell enlargement. Adequate phosphate also promotes early root formation and growth.

Plants absorb most of their P as the primary orthophosphate ion (H2PO4-). Smaller amounts of secondary orthophosphate ion (HPO42-) are taken up. Other forms of P can be utilized, but in much smaller quantities than orthophosphate.

There are many excellent sources of phosphate fertilizer. The selection of a particular product depends on price, physical characteristics, and nutrients accompanying the phosphate. Agronomic studies have shown that there is no significant difference in plant response to common phosphate fertilizers if they are used properly. The most common fertilizers include:

Diammonium phosphate (DAP) DAP is the world’s most widely used P fertilizer. It is made from two common constituents in the fertilizer industry and it is popular because of its relatively high nutrient content and its excellent physical properties.

Molecular structure of diammonium phosphate


Diammonium phosphate fertilizer

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

Molecular structure of monoammonium  phosphate

Monoammonium phosphate fertilizer


 • Ammonium polyphosphate (APP) When phosphoric acid and ammonia are reacted, water is driven off and individual phosphate molecules begin to link together to form a polyphosphate fluid fertilizer.

Polyphosphate fluid fertilizer
    Triple superphosphate (TSP) TSP was one of the first high analysis P fertilizers that became widely used in the 20th century. It is an excellent P source, but its use has declined as other P fertilizers have become more popular.
Triple superphosphate
  The use of regular soil testing and consultation with a local certified crop adviser will provide guidance on how to best manage the phosphate supply for your crops. The next time you apply phosphate fertilizer, consider the complex journey that it took to get those nutrients to your plants.

A visual tour of the phosphate production process can be seen at this URL:


Declining soil fertility threatens Uganda’s food security

Rice with phosphorus fertilizer (L) and in the native soil (R)

Declining soil fertility threatens Uganda’s food security

An interesting article appeared in the "Daily Monitor" about the necessity of providing an adequate supply of nutrients to crops.
The scientific issues are pretty straightforward, but the political, social, and economic hurdles are a real challenge.

There is a declining trend in food production in Uganda today mainly attributed to reduced soil fertility.  Given  that 70 per cent of Uganda is engaged in subsistence farming for food production, the declining soil fertility has serious socio-economic consequences on livelihood. 
“As you may be aware, low and declining soil fertility is one of the most limiting factors to agriculture production and productivity apart from overgrazing, over cropping and soil erosion across Uganda,” Mr Komayombi Bulegeya, the commissioner of Crop Protection at the Ministry of Agriculture, said. He was speaking during a one-day workshop on the development of national fertiliser policy, regulation and strategy for Uganda in Kampala last week.

He said food production is growing less than 3 per cent annually yet the population is increasing at the rate of 3.2 per cent annually and this is bound to cause mass food shortage.
To avert the problem, Mr Komayombi recommended the use of both organic and inorganic fertilizer.
“We must use fertilisers in order to reverse the declining nature of our soil so as to enhance food security, farmers’ incomes and widening agriculture export base,” he said.
Low use of fertilisers
Uganda uses only one kilogramme per hectare annually compared to Tanzania which uses 6 kg/ha annually and Kenya 32kg/ha contrary to the recommended volumes of 200kg/ha/year.

The poor use of fertilisers in Uganda, according to experts, has mainly been caused by farmers misconception that Uganda’s soil is still fertile.  Financial challenges also hinder the use of fertilisers because the ordinary farmer can not afford a bag of fertilisers.  Farmers, however, say the level of counterfeit farm inputs on the market have discouraged them  from using fertilisers.

“Often most of the fertilisers being supplied add no value to the soil yet they are very expensive,” one of the farmers who attended the workshop told Business Power.
The fact that Uganda is landlocked, the rising cost of road transport and the fact that fertilisers are on demand seasonally have discouraged traders into venturing in that line of business. 
Soil sampling
Dr Peter Ebanyah, a lecturer in the department of agricultural productivity at Makerere University advised farmers to find out the nature of their soil composition before they buy fertilisers.
“It’s not just about using any fertiliser you come along since they all contain different mineral and nutrients and the wrong administration of these inorganic fertilisers will not improve your soil fertility,” he said.
“Conducting soil testing is very important in order to make the right purchase. Also, there are times when the soil has degraded a lot and in such a case it advisable to use both organic and inorganic fertilizers to boost the soil fertility.”
Dr Sarah Ssewanyana, the executive director Economic Policy Research Centre, recommended that there is need of having a national policy and regulation to guide and promote increased use of fertilisers use in Uganda.
Annually, the country imports about 25,000 metric tonnes of fertilisers. 80 per cent goes to the tea, sugarcane and coffee estates while the small farmers who are the main food producers only get 20 per cent and thus the need for the government and other stake holders to formulate good policies that will facilitate the ordinary farmer to access good and affordable fertilisers.

Tuesday, February 15, 2011

Urea fertilizer... the basics

Urea is the most widely used solid N fertilizer in the world. Urea is also commonly found in nature since it is expelled in the urine of animals. The high N content of urea makes it efficient to transport to farms and apply to fields.
The production of urea fertilizer involves controlled reaction of ammonia gas (NH3) and carbon dioxide (CO2) with elevated temperature and pressure. The molten urea is formed into spheres with specialized granulation equipment or hardened into a solid prill while falling from a tower.

During the production of urea, two urea molecules may inadvertently combine to form a compound termed biuret, which can be damaging when sprayed onto plant foliage. Most commercial urea fertilizer contains only low amounts of biuret due to carefully controlled conditions during manufacturing. However, special low-biuret urea is available for unique applications.

Urea manufacturing plants are located throughout the world, but most commonly located near NH3 production facilities since NH3 is the major input for urea. Urea is transported throughout the world by ocean vessel, barge, rail, and truck.
                 Chemical Properties
                    Chemical Formula:           CO(NH2)2
                    N content:                         46% N
                    H2O Solubility (20ºC):       1,080 g/L

Agricultural Use
Urea is used in many ways to provide N nutrition for plant growth. It is most commonly mixed with soil or applied to the soil surface. Due to the high solubility, it may be dissolved in water and applied to soil as a fluid, added with irrigation water, or sprayed onto plant foliage. Urea in foliar sprays can be quickly absorbed by plant leaves.

After urea contacts soil or plants, a naturally occurring enzyme (urease) begins to quickly convert the urea back to NH3 in a process called hydrolysis. During this process, the N in urea is susceptible to undesirable gaseous losses as NH3. Various management techniques can be used to minimize the loss of this valuable nutrient.

Urea hydrolysis is a rapid process, typically occurring within several days after application.  Plants can utilize small amounts of urea directly as a source of N, but
they more commonly use the ammonium (NH4+) and nitrate (NO3-) that are produced after urea is transformed by urease and soil microorganisms.
Management Practices
Urea is an excellent nutrient source to meet the N demand of plants. Because it readily dissolves in water, surface-applied urea moves with rainfall or irrigation into the soil. Within the soil, urea moves freely with soil water until it is hydrolyzed to form NH4+. Care should be used to minimize all N losses to air, surface water, and groundwater. Avoid urea applications when the fertilizer will remain on the soil surface for prolonged periods of time. Undesired N losses may also result in loss of crop yield and quality.

Urea is a high N-containing fertilizer that has good storage properties and causes minimal corrosion of application equipment. When properly managed, urea is an excellent source of N for plants.

Non-agricultural Use
Urea is commonly used in a variety of industries. It is used in power plants and diesel exhaust systems to reduce emission of nitrous oxide (NOx) gases. Urea can be used as a protein supplement in the diet of ruminant animals, such as cattle. Many common industrial chemicals are made using urea as an impor­tant component.

Urea on the soil surface

Wednesday, February 9, 2011

Where does potash fertilizer come from?

Potassium chloride

Potassium deficiency symptoms (cotton)
Maintenance of an adequate K supply in the soil is essential for sustaining global food supplies. Many soils need an additional source of K to supplement the native minerals in order to meet this minimum requirement. Crops remove large amounts of K from the soil in the harvested portion.

At some point, it is necessary to replenish the supply of this nutrient.
Solar evaporation ponds (Utah)
Deep potash mines (Belarus)
Potassium fertilizer (commonly called potash) is mined from underground deposits in many parts of the world. Canada is the largest producer of potash fertilizer, followed by Belarus, Russia, and China. The potash ore is extracted from depths exceeding one-half mile below the earth’s surface.

The potash ore is first crushed and washed to remove any clay or minerals that may be present. Some potash ore contains iron that imparts a red tint to the final fertilizer. The sodium salts are next separated and removed from the potash. The potash particles are then compacted to achieve the desired size for convenient handling and spreading.

A few naturally occurring surface-water brines (such as the Great Salt Lake in Utah and the Dead Sea bordering Jordan and Israel) contain sufficient K to make potash extraction feasible. Solar evaporation is used to concentrate the salts, which are washed to separate the K salts from the sodium salt.
Potash storage before export

Potassium has many important functions in plants. Perhaps the most noted roles are for regulating plant water relations, activating enzymes, and promoting protein formation. Potassium also plays a significant role in improving the quality of the harvested plant products and enhancing disease and insect resistance.

The finished potash fertilizers are important global commodities that are transported across the world. China is the largest potash consumer, followed by the USA, India, and Brazil. There are many excellent potash fertilizers available; the selection depends on the agronomic need of the crop.
Two grades of potassium magnesium sulfate
The K portion of all potash fertilizer is identical, the difference being the anion present. The most common fertilizers include: Potassium Chloride (KCl); Potassium Sulfate (K2SO4); Potassium Magnesium Sulfate (K2SO4 •2MgSO4); and Potassium Nitrate (KNO3).

The results of regular soil testing and consultation with a local Certified Crop Adviser (CCA) will provide guidance on how to best manage the K supply for your crops. The next time you apply potash fertilizer, consider the complex journey that it took to get those nutrients to your plants.

A visual tour of the potash production process can be seen here.

Thursday, February 3, 2011

Managing Plant Nutrients...Welcome

Welcome to the new blog
I'll post some of the interesting information I come across related to managing plant nutrients and some of the things I develop for the International Plant Nutrition Institute.  You might want to check out the website too.