Do You Need to Know How to Fertilize your Grass?

by admin on March 22, 2011 · 1 Comment

in advice, All Posts, Grass and Lawns, Problems and Solutions

Do you want a green lawn?

Excerpt from my ebook Growing Great Lawns

One of the most important factors in growing a great looking lawn is how much and how often to feed it.  The fertilizer companies have every one convinced that it takes a rocket scientist to figure this out.  I’m here to tell you that is all BS.

Fertilizing you lawn is really quite a simple process and one I always looked forward to.  Let me simplify it for you.  Your lawn will grow okay without any fertilizer at all BUT IT WILL NOT BE GREEN. Most of the elements your lawn needs will be supplied by the soil air and water, most but not all.

The amount of Nitrogen (N) that is available to your grass is the most important factor to having a nice looking lawn. If it has enough it will be happy and green if not, it will be pale and sad looking. So how do we add nitrogen? Well, commercially manufactured fertilizers are the best option. The problem is that the fertilizer manufacturers have no standardization.

The range of blends and types of nutrients varies widely, luckily, there is one thing you can use as a guide. All fertilizer bags have three numbers listed on them. It is usually on the front or perhaps on the ingredient list on the back of the bag but the should be prominently posted.

These three numbers are the amount of Nitrogen (N), Phosphorus (P) and Potassium (K) shortened to NPK contained in the bag. The bag will show the percentage of each of these three elements that are available in the fertilizer. Remember we are mainly concerned with the Nitrogen to get the green color we want and nitrogen is the first number listed. Here is a problem. He can’t just buy a fertilizer that is high in nitrogen and use it all year around. Nitrogen availability is dependant on temperature. In the colder times of year less will be available so we must use a higher level and in the warmer growing seasons you will need less or your grass will grow too fast (think Jack and the Beanstalk fast).

Let me make this simple for you. I suggest that you apply only two types of fertilizer and only change from one to the other once a year. Forget all the fancy mixtures and blends and avoid any seasonal ‘specials’ just follow these instructions and remember that your goal is to apply about 1lb of actual nitrogen each time you fertilizer. (calculation in the appendix)

When the grass is actively growing, use a mixture that is labeled 16-6-8. That’s 16% nitrogen 6% phosphorus and 8% potassium. Now don’t be surprised if you go to buy fertilizers and can’t find anything with these exact numbers, you probably won’t because it is a commercial blend. Just get something close as possible (16-4-6, 18-6-6, etc.) Remember the Nitrogen is the important element here so as long as you get something in the range of 16% to 21% nitrogen you will be fine. Don’t worry about the other two elements they are not what’s important here, just pay attention to the amount of N.  That mixture should be good for the warmer seasons then, when it starts to cool off you will need to shift to a higher N level. This one is simple. Just get the highest level of N you can for the lowest cost. 46-0-0 is a good one, 36-0-0 is another. The P and K aren’t available when it is cold and the N will be all that is needed. Remember, don’t use the high Nitrogen fertilizer in the warm seasons as the grass will grow so fast it will begin to look shaggy the day after you mow it.

There will be a bunch of formulation that garden centers will try to push on you, timed-release, slow-release, urea based and on and on. Go ahead and learn all about them if you want but if you follow my instructions you will be fine. If you can afford to pay a little more the best fertilizers are a combination of fast release and slow release materials. For the slow release component look for the letters IBDU, sulfur coated or water insoluble on the bag. They are pricy but last longer.

Fertilizer frequency is also important. The trick is to keep a uniform color and avoid the ups and downs of yellowing between fertilizer applications.. A good rule of thumb is to apply every six weeks in the growing seasons and every eight or ten weeks when the turf is not actively growing.  If you want to get more detailed than that I have provided a set of calculations in the appendix for fertilizer amounts but if you follow these instructions you probably won’t need to get more detailed than this.

Signs of fertilizer deficiency: If you are mowing your lawn regularly you will see that following a fertilizer application your grass will grow faster and you will have more clippings to depose of. When you start to see a sharp drop in the amount of clippings you will know your fertilizer is running out. If you begin to see a yellow returning to your lawn that is a sign you need to re-apply quickly.

This is a  excerpt form my book Growing Great Lawns,  and here is a link to another article I wrote on lawn care.

Happy Mowing 🙂


B. Gutatta

Thanks Rees,
My lawn looks horrible and I really want it to look good this year. We have had above average rainfall here in California and I hope it will continue. I will try your suggestions on fertilizer.

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