What is fertilizer?
Every bag of fertilizer has a set of numbers called N – P – K; Nitrogen – Phosphorus – Potassium (Potash). The numbers represents the percent of that macro-nutrient in that particular bag. These nutrients are essential to plant health. Some bags of fertilizer may also contain micro-nutrients and/or pesticides. The type of fertilizer, weather, and the actual property all play a role in timing of an application in order to keep grass attractive and resilient.
Too much fertilizer or too little, both can be detrimental for a lawn. You want to decide on the right fertilizer, at the right time of year in order to be efficient and most beneficial. Temperatures effect which nutrients to use (N – P – K) and how slow the fertilizer releases. The way fertilizer is coated effects the release of nutrients, dictating how long fertilizer can stay in the soil. Depending on the time of the year, you may want a slower/faster release fertilizer. Fertilizer can stay in the soil anywhere from 4-6 weeks, but rain/water will cause nutrients to leach faster. This is one reason why over-watering can be bad. The minimum, by law, is a 20% slow release fertilizer.
Other laws in New Jersey are limitations on phosphorus, only being allowed to apply it with seed or if you have a soil test and results show a deficiency. Only 1 pound of nitrogen can be applied at once per 1,000 square feet. New Jersey law even states that fertilizer can only be applied between March 1st and November 30th. These laws were put in place to prevent algae from forming in waterways, which was hurting our ecosystem.
How do these macro-nutrients help my lawn?
Nitrogen promotes plant growth. Nitrogen is part of every protein in the plant, which is part of every process, from growing new leaves to defending against pests. Nitrogen is also part of the chlorophyll molecule that is involved in creating food through photosynthesis, giving plants their green color. Older grass tends to have less mobility of resources within the plant. This could lead to more yellowing at the end of the season, before dormancy, when grass reaches a certain age.
Phosphorus promotes new growth and root growth,. Root development leads to winter hardiness and improves the defense against other environmental stresses, including disease. Phosphorus is required for establishing roots, seed development, cell division, and the synthesis process used by plants. Phosphorus is not very mobile in soils, so it doesn’t have to be applied regularly.
Potassium is what keeps our grass strong. This nutrient is involved in cellular metabolism, environmental stress resistance, disease resilience, internal water management, and wear tolerance. It reduces transpiration, so grass needs less water. Potassium also stimulates plant enzymes used in protein, sugar, and starch synthesis. Being deficient in potassium could lead to permanent injury from drought, winter, traffic and/or disease.
Why is soil pH so important?
The pH is most important factor in growing grass since it affects the availability of nutrients in the soil that are essential for plant growth. Optimum range soil pH should be for grass is 6 – 6.6 on the pH scale. Depending on how acidic soil is, grass may not even be receiving nutrients from the fertilizer. Other than the pesticides that are sometimes included with fertilizer, some may just be wasting their money fertilizing if they have acidic soil! This is why having the soil tested is extremely important. Once at optimum level; the next time you seed you will have better results, grass will thrive and be more durable. Even weed controls will work better!
If your soil is too acidic, lime is recommended. Sometimes multiple applications are recommended when soil is very acidic. Please keep in mind, each lime application may take 6 months to fully correct the soil pH and 50 pounds per 1,000 square feet is the most that can go down at one time without wasting. If indeed multiple applications of lime are needed, they would have to be spaced out 6 months apart to efficiently correct the soil pH. Lime can be done anytime of the year and will not burn grass if incorrectly applied. Can you apply too much lime? Yes, if the soil was already neutral or alkaline and lime was applied on a regular basis. Over applying one application would just waste money. So don’t assume a heavy dose of lime is needed annually and have soil tested!
Micro-nutrients included in lime:
This usually goes hand in hand with soil pH, but not always. Calcium plays a major role in the physiology of grass, strengthening its physical structure, increasing nutrient uptake and protecting grass from disease.
If this nutrient is needed, dolomitic limestone would be applied instead of your usual calcitic lime. Dolomitic lime contains calcium, but higher levels of Magnesium. Magnesium is a carrier of phosphorus in plants, regulates the absorption of calcium and plays a major role in photosynthesis.
Would my neighbor have a similar soil analysis?
They could, but most likely not. Just about every property is different. Here are some factors that could make one property different then their neighbors:
- It depends on what kind of plants and trees are on the property. Oak trees and evergreen trees/shrubs will make the soil acidic.
- What a homeowner or the previous owner applied on the property throughout the years will pay a huge role. For example, topsoil being applied.
- Fertilizer could even make the soil acidic and will be a factor as to how much nutrients are in the soil.
- The way a property is sloped, leading to runoff of nutrients.
- Irrigation (over watering) could lead to leaching of nutrients.
- Construction may make the soil acidic as well. Soil a foot or more down that is disturbed and is exposed to oxygen can lead to a chemical reaction, causing soil to become acidic. A new house being built, a pool being installed, and any kind of excavating are examples of how the soil can be introduced to oxygen for the 1st time.
Find out more about soil testing, please visit Rutgers Soil Testing Laboratory.