“What kind of fertilizer should I use and how much”?
A good question and pretty basic information for every hydroseeding contractor to know. So why does this subject seem confusing to many hydroseeders?
The first thing to understand is hydroseeding is just one of many methods to plant grass and other vegetation. This method of planting grass was introduced over 60 years and became most popular in the early 1990s. Those of us in the hydroseeding industry believe it is the most efficient and cost effective way to plant grass.
1. It is easier to access hard to reach areas
2. The application process is faster
3. The fertilizer is applied with all of the other ingredients more evenly in a one step process
4. Reduced labor cost
5. It is easier to apply tackifier products that will hold the applied products and soil in place while awaiting germination
Fertilizer is usually expressed in terms of N (nitrogen) P (phosphorus) and K (potassium) and the percentage of these nutrients are printed on the bag in easy to read bold print. Other essential nutrients are usually listed in small print somewhere on the bag.
Before choosing your fertilizer it is very important to take random soil samples from the job site and send the samples to a professional soil-testing lab for analysis and nutrient recommendations. The samples should be randomly taken over the entire job site to a depth of 2 to 3 inches. The soil test will determine soil pH, fixed nutrient levels in the soil and will identify soil contamination that might be present.
If soil testing is not done a starter fertilizer should be used to help the new seedlings establish rapidly. A standard starter fertilizer normally has an N-P-K analysis expressed in a 1-2-1 or 1-3-1 ratio, such as 15-30-15. The reason to use these N-P-K ratios is these are the same ratios of N-P-K that are found in establishing grass plants.
The rate of fertilizer that is used is usually expressed in terms of pounds per one thousand square feet. The soil test recommendation will tell you how much of each nutrient is required per thousand square feet. If a soil test is not done, a fertilizer should be used with starter N-P-K ratio. Nitrogen is generally the nutrient that gets the most attention when fertilizer is applied to established turfgrass. However, when seed establishment is the goal, phosphorus is the most important nutrient to consider. Two pounds of actual phosphorus per 1000 square feet is recommended for the rapid establishment of new seedlings. If your fertilizer has a 1-2-1 or 1-3-1 ratio then N & K nutrients will naturally go down at the appropriate rates. A soil test may not recommend two pounds of phosphorus, but without a soil test it is important to provide the quantity of phosphorus that the grass seedlings will use during the establishment process.
Use this formula to determine how much total fertilizer is required if the key ingredient, in this case phosphorus, is applied at the rate of 2 pounds per thousand square feet. The application rate – times the area in terms of 1000 sq. ft. segments – divided by the percent of phosphorus in the bag = the amount of total fertilizer needed. If you have a fertilizer with an analysis of 15-30-15 and need to know how much total fertilizer to use in a hydroseeder that covers 10,000 square feet (800/900 gallons), just enter the known numbers into the formula and do the math.
(2 x 10 = 20) divided by .30 = 66 pounds of total fertilizer
This formula is more commonly used when applying fertilizer to existing turf where nitrogen is the key nutrient, but will work for any nutrient.
When applying fertilizer through a hydroseeding machine an agriculture grade fertilizer will work very well. It is not necessary to use the more expensive turf fertilizers with uniformly shaped granules. These fertilizers are meant to be applied in the dry form because they allow for better dry application coverage than fertilizers with granules of varying sizes. Particle size does not matter when hydroseeding because water is the carrier for the various nutrients.
The less expensive, quick release, agricultural grade fertilizers work very well as compared to the more expensive slow release nitrogen fertilizers. Remember the nutrient that we are concerned about when planting grass is not nitrogen, but phosphorus, which is not available in a slow release form. Agricultural grade, quick release fertilizer will do the job that is required providing food for the seedlings for eight to ten weeks during the establishment period. The added benefit to agricultural grade fertilizer is it contains all of the essential nutrients that are required by the grass plant. Slow release nitrogen fertilizers do not last any longer in the soil, but they do provide a more even release of the nitrogen, which is desirable for established turfgrass, but not necessary on a newly planted site. Remember that your goal is rapid plant establishment and quick release fertilizers are a better choice for this purpose.
As discussed, phosphorus is the key nutrient to consider when planting grass. Contractors should be aware that there are some communities that have laws limiting or prohibiting its use. These laws are more common in areas where phosphorus run off into rivers, streams and lakes is a concern. We recommend that you check with your local authorities before using phosphorus on a hydroseeding project.