When it comes to nitrogen fertilizers, they are classified based on the rate at which the nitrogen is released, specifically its accessibility to plants. Buy smart pots The two broad types are slow-release nitrogen and water-soluble nitrogen.

Right after watering it in, water-soluble nitrogen is readily available and promotes the growth and dark green color of the lawn. For soluble fertilizers, the effect of nitrogen does not last very long, which is why it is necessary to apply the fertilizer frequently in small amounts to regulate the required supply of nitrogen to the lawn. Ammonium nitrate, ammonium phosphate, urea, and ammonium sulfate are some examples nitrogen fertilizer components that are water-soluble.

The salt-like characteristics of water-soluble fertilizers are the ones that cause burning or desiccation injury as it draws out the water from leaf tissues. When the turf is moist and urea or ammonium sulfate is applied, the problem occurs when people do not immediately water the lawn. To avoid foliar burn, the turf should be thoroughly irrigated after any water-soluble fertilizer is applied. One will know whether the lawn is watered long enough when the granules are washed off the foliage, or have become completely dissolved.

The characteristics of slow-release nitrogen fertilizers on the other hand are low water solubility therefore the nitrogen is slowly released over an extended period of time than that of soluble fertilizers. This means that the growth response and change in color intensity is slower and fertilizer burn is less likely to occur. Also, this type of fertilizer is much more expensive while water soluble nitrogen fertilizers are much more affordable.

Nitroform and Nutralene or methylene ureas are the common forms of slow release nitrogen fertilizers together with SCU or sulfur coated urea, PCSU or polymer coated SCU, PCU or polymer coated urea, IBDU or isobutylidenediurea, and other protein based, natural, and organic sources like mixtures of feather meal, dried blood, activated sewage sludge, and dried poultry waste.

When the soil microorganisms break down the synthetic methylene ureas, the nitrogen is released. In warm or hot weather, the microbes are more active, thus making it more effective in the summer and less effective in spring and winter.

The release of the SCU nitrogen is almost entirely dependent on the water that allows the sulfur shell to dissolve the urea. The nitrogen is released at higher temperatures faster by these products, and compared to slow release sources, the nitrogen is released faster by the common SCU materials. This kind of source is common in many kinds of fertilizers.

In dissolving the urea, the water that passes through the polymer shell is where the PCU and PCSCU rely on to be diffused in the soil. Next, the nitrogen will be absorbed by the roots of the plants. In warm weather, the nitrogen is released faster and slows down significantly when the temperature of the soil drops to around 40 degrees Fahrenheit.

As for IBDU, it depends on the process of water hydrolysis in order for the nitrogen to be released. Compared to polymer coated or natural fertilizers, the soil temperature has no effect on the nitrogen that needs to be released. No matter what time of the year, IBDU is highly effective to be used. In applying it for the first time, the response may be weak, but is very effective after repeated application over a long period of time.

When the soil microorganisms break down the protein based natural products, the nitrogen is released. This means that these products are highly dependent of the temperature, releasing nitrogen faster in the summer and fall months wherein the temperature of the soil is high. The effects are similar to the useof PCU, PCSCU, methylene ureas, and IBDU. In Oregon, these organic and natural materials are widely used.

Both slow release and soluble sources of nitrogen are combined in commercial products to achieve a fair initial response and lasting effects. Intermediate cost and lower risk for burns are among the other benefits of using commercial fertilizers.

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Phosphorus does not have any effect on the growth or color on a healthy turf. In contrast to what has been stated in garden books, magazines, and newspaper articles, the growth of the root in grasses is not enhanced by phosphorus, unless this component is added to a turf that is already deficient in Phosphorus. There is an adequate amount of Phosphorus in a wide range of lawns, making supplemental applications a waste.

When the soil tests indicate a low amount or deficiency, then it is the best time to apply phosphorus. For all Oregon regions, a soil test that indicates a phosphorus level that is above 20 ppm means that there is an adequate amount and there is no need to make supplementary applications.

In case the need to apply supplementary phosphorus arises, it should be used sparingly. A functional turf hardly benefits from an excess of 1 pound of P2O5 in every 1000 square feet each year.

When fertilizers are said to be “complete” it means that they contain potassium, phosphorus, and nitrogen. For frequent applications on lawns, use fertilizers that have little or no phosphorus. On commercial products, phosphorus is labeled as P2O5, also known as phosphoric acid. Commercial products that have the same or similar ratios to 15-15-15 should be avoided because they contain excessive amounts of phosphorus that average lawns need. These products also increase the possibility of phosphorus pollution in surface waters.

In choosing composts and natural or organic fertilizer products, one must be extra careful as these products contain excessive high levels of phosphorus.

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For a healthy turf, potassium is another important component that is applied in huge or abundant amounts. Although it does not have any effect on the growth or color intensity of the lawn, potassium is known to enhance the resistance of plants to extreme weather conditions such as heat or cold. It also reduces the risk of wilting from drought and increases the wear tolerance of the turf.

In Oregon, a general rule is that the potassium level in soils that are below 250 ppm is in an indication for fertilization with potassium. Using this standard as the basis, many of the lawns in the eastern part of Oregon do not require potassium fertilizer. On the other hand, the soil potassium in western Oregon is low, indicating a regular application for the fertilizer.

The application rates for potassium should be equivalent to two thirds of the nitrogen rate. For example: for every 3 pounds of nitrogen, there should be 2 pounds of potassium. A commercial fertilizer with a label that has a 12-3-8 will have an appropriate ratio of nitrogen to potassium. Remember that in commercial products, potassium is labeled as K20, also known as soluble potash.

Iron (Fe)

Iron is used in very little amounts as required, that is why it is called a micronutrient. Turfgrasses with deficientcy in iron is not very common, but is possible to occur on soils with pH level greater than 7.0 like in eastern Oregon. A high pH level in soil indicates that there is limited availability of iron to the plants.

For commercial fertilizers, iron is a common component because the greening response is quickly noticeable. In most fertilizers, soluble iron is present and is noticeable because of the brown stains on driveways and concrete sidewalks when applied with water. The removal of these stains is difficult to remove, and can be expensive when purchasing stain removal solutions or hiring the services of experts. One of the best ways to prevent stains is to buy fertilizers that do not contain iron. If you are already using a fertilizer that contains iron, you can prevent stains by blowing the fertilizer back to the soil before irrigation.

How can I decipher a fertilizer label?

According to state law, fertilizer bags should have appropriate labels printed with the necessary information. One of its main purposes is to give the consumers a guarantee that what they are paying for is contained in the product, based on the printed labels. If the contents are analyzed and do not match what the label indicates, the state will charge fines to these fertilizer companies. All commercial fertilizers have key information printed on the labels. Before choosing, you may want to compare several products first to find out how each one is different from another.

For a well-balanced and fertile turf, a ratio of 6-1-4 in complete fertilizers must contain nitrogen, phosphorus, and potassium. For other popular brands, the potassium content may be lower, but consumers can be confident in using complete fertilizers with ratios like 6-1-4 and 8-1-2.

For winter, spring, summer, and fall, fertilizers are marketed according to these seasons. Slow release nitrogen is a major component in summer fertilizers. Winter fertilizers have more potassium content than fertilizers for other seasons. The truth is, this adjustment in fertilizer content has no effect on the soil, but rather a marketing strategy by companies to encourage consumers to buy several different products for every season of the year. Staying with an efficient fertilizer ratio is enough to be used all year round, still getting the results of a functional and a beautiful turf.

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Both calcium and magnesium hardly have any effect on the color intensity and growth of grass. These components mainly impact the pH level on the soil. When applied as limestone, the pH acid level of the soil is indirectly raised and the turf fertility is improved.

For turfgrasses that grow in varying ranges of soil pH, the optimum range is the most significant mainly because the soil retention of the needed nutrients and the availability for growth of the turfgrass is increased.

An acidic soil means that there is a low pH level. These are common in the western and coastal parts of Oregon, and are quite rare in the eastern and central parts.

If the pH value from the soil test indicates that it is below the average range for lawn grass, the pH level will rise with the help of a lime application. With the use of lime, it will usually take at least 2 years for the pH level of the turfgrass to change. The reason for this is that lime cannot be mixed into lawn soil because it is not very soluble.

Dolomitic limestone and agricultural limestone are the two common types of lime. Calcium and magnesium are both present in dolomitic limestone while agricultural limestone contains only calcium.

In order to determine which type of limestone to use, getting a soil test for magnesium and calcium is recommended. Agricultural limestone is used for soil with magnesium levels exceeding 1.5 meq per 100 grams of soil. Dolomite is used if the magnesium level is lower than 1.5 meq per 100 grams of soil. In Oregon, areas where there is magnesium deficiency are on the coastal counties, and these are the places where dolomitic limestone will be beneficial.

For another general rule, the maximum lime application is at 50 pounds lime for every 1000 square feet. For an established turf, the total application in one year will be 100 pounds lime in every 1000 square feet. Split applications are required between the spring months and fall months in order to prevent the accumulation of lime at the surface of the soil.

After liming, urea or ammonium sulfate found in nitrogen fertilizers should not be applied as the lime is still present in the soil, it may cause the ammonium to vaporize, and evaporate in to the atmosphere.

Optimum soil pH ranges for commonly grown turfgrasses:
(Type of grass – optimum pH range)
Bentgrasses: 5.0 – 65.
Perennial ryegrass: 5.5 – 6.5
Fine fescues: 5.5 – 6.5
Tall fescue: 5.5 – 6.5
Annual bluegrass: 6.0 – 7.0
Kentucky bluegrass: 6.0 – 7.0

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