Below is a lot of information about fertilizers, compost, lime requirements and more.
Slow-Release Nitrogen Sources
If you are confused by all the different slow-release nitrogen sources that are available, you aren't alone. Below I have provided some information on 5 common sources of slow-release nitrogen.
Probably the most frequent question I get is about the application rates. A customer will call and tell me they need to apply 1 lb. of nitrogen per 1000 sf. Because they don't do it often enough, they forget how to figure it out. Below are some examples that will hopefully help. However, you are always free to call and ask.
It also important to know conversion information or have that information handy. Click here to view a printable version of Conversion Information.
1st number of the analysis - Nitrogen
2nd number of the analysis - Phosphorous
3rd number of the analysis - Potash
Remember that a fertilizer analysis is given in percentages. Take 10-10-10 for example. If you have a 50 lb. bag of 10-10-10, you will have 5 lbs. of nitrogen, 5 lbs. of phosphorus and 5 lbs. of potash in the bag. 50 lbs. times 10% (.10) = 5 lbs.
Using 18-18-18, take 50 lbs. times 18% (.18) = 9 lbs. each, nitrogen, phosphorus and potash in the bag. Square Feet per acre: 43,560 sf or 43.56 thousands (43,560 divided by 1000)
Pounds needed: 1 pound of nitrogen per 1000 sf needed. 1 lb. times 43.56 = 43.56 lbs. of actual nitrogen needed per acre.
Fertilizer being used: Let's say you are using 18-24-12. The first number is the % nitrogen in the blend - 18% (.18). Take your nitrogen needs from above (43.56 lbs.) and divide by 18% (.18) = 242 lbs./acre 18-24-12 needed to get 1 lb. nitrogen per 1000 sf.
2nd example: Now try an example using 26-4-18 and apply 1-1/2 lbs. of nitrogen per 1000 ft. Take 43.56 times 1.5 lbs = 65.34 lbs. of actual nitrogen per acre needed. 65.34 lbs. divided by 26% (.26) = 251.30 lbs./acre 26-4-18 needed to get 1 lb. nitrogen per 1000 sf.
3rd example: What if a soil test result shows that you need to apply 2 lbs. of phosphorus per 1000 sf. The second number in a fertilizer analysis is the phosphorus level. The third number is the potash level. You are using 18-24-12 as your fertilizer source. In this example, the phosphorus level in the blend is 24% (.24).
First, take 43.56 and multiply by 2 lbs. = 87.12 lbs./acre of actual phosphorus needed. Divide 87.12 lbs. by 24% (.24) = 363 lbs./acre needed of 18-24-12.
4th example: When you apply 363 lbs. of 18-24-12, how much nitrogen and potash are you applying? We already know you are applying 2 lbs./1000 sf of phosphorus from example 3 above.
363 lbs./acre of 18-24-12
363 times 18% (.18) = 65.34 lbs. of nitrogen per acre or 1.5 lbs per 1000 sf.
363 times 24% (.24) = 87.12 lbs. of phosphorus per acre or 2.0 lbs per 1000 sf.
363 times 12% (.12) = 43.56 lbs. of potash per acre or 1.0 lb. per 1000 sf.
Click here for printable version of examples above
Fertilizer Conversion Table
|Pounds of Product|
|Fertilzer Analysis||Per 1,000 sf (1)||per acre (2)|
|29-3-5 w/ SCU||3.45||150|
(1) Amount of product needed to apply 1 pound of nitrogen per thousand square feet.
(2) Amount of product needed to apply 43.5 pounds of nitrogen per acre. To determine the amount of product needed to deliver 1 pound of nitrogen per thousand square feet, divide 100 by the first number in the fertilizer ratio. For example, for 16-4-8 fertilizer, divide 100 by 16. The result is 6.25 pounds of product per thousand square feet.
pH & Soluble Considerations
With the chart above, it is easy to see how improper pH levels can effect soil nutrient uptake by the grass plant. The old saying among farmers is if you don't have a proper pH, don't waste your money on fertilizer.
Although the chart shows optimum soil pH around 6.4, research has shown that turf does the best around 6.0.
Pounds of Limestone to Add
per 1000 sf to Raise Soil pH to 6.5
Pounds of Elemental Sulfur to Add
per 1000 sf* to Reduce Soil pH to 6.5
|Original pH||Sandy Soil||Clay Soil|
*The recommended rates for sulfur are only for bare ground application
If applying on existing turf, rates should not exceed 2-3 lbs./1000 sf.
Pounds of Gypsum to Add per 1000 sf
to Reduce Soluble Salts to Recommended Levels
Original Salt Levels
in Parts Per Million
Pounds of Gypsum
per 1000 sf
Click here for printable version of the charts above.
Soil Texture Triangle
Several times a year, I get the question asking what texture makes the best soil. The answer isn't as easy as one would think. It all depends on what the soil is being used for. In this case though, let's assume that it is going to be used to establish turf for a home lawn or commercial property, not necessarily an athletic field.
The relative proportion of various grain sizes in a soil is called texture. To describe texture, names such as loamy sand, silt loam, clay loam and silty clay are used. You can see these categories in the soil texture triangle above.
The best soils are generally those that contain 10-20% clay, with silt & sand in approximately equal amounts, and a fair amount of organic matter. Therefore, a "loam" soil is considered a very good soil.
What is a fair amount of "organic matter"? For establishing and maintaining turf, I prefer soils with 3.0-4.0% organic matter. Levels below 3.0% tend become more compacted, holding less moisture and making it more difficult to maintain a healthy turf, particularly during stress periods.
Below I talk about how to raise the organic matter in soils with low levels. It can get a little complicated, depending on the compost being used and the depth that the compost is being worked into the soil.
Incorporating Compost Into Soil
Adding compost to existing soil or to soil being applied to an existing site is very common. Many of the soils that we are working with in the Mid-Atlantic region are low in organics and need to be amended. The question is, how much do you need to add.
Let's say that you having and existing soil with an organic matter of 1.0%. The spec calls for you to bring the organic matter level to 4.0% in the top 4" of soil. How do you figure out how much compost to add per acre?
Below I have given some amounts of compost needed to bring soil up to 4.0% organic matter. At some point, I will attach an Excel file that will allow you to plug in your parameters and get your answer immediately.
% Organic Matter
in Existing Soil
% Organic Matter
Required by Spec
Depth of Soil
In many situations, it is impossible to incorporate compost into the existing soil. Most frequently you have an existing stand of turf and do not want to destroy it. However, soil test results show that the organic matter is low and needs amending. You can accomplish this by top-dressing compost over the top. Depending on how low the organic matter is, you may need to top-dress a 1-2 times per year for several years to get the desired results.
Below are compost requirements for various depths of application. Keep in mind that you should not apply more than 1/2" on existing turf.
|Depth of Compost Desired||Amount of Compost Needed per Acre|