Basic guidelines for growing a good looking lawn

 2.  The more nitrogen and water you apply the more the grass will grow, and the greener it will look.  If you apply too much Nitrogen and water, the plant will take it up and grow too fast, which weakens its internal immune system and encourages disease.   Obviously more nitrogen and more water cost more money.  Using these inputs efficiently can minimize the costs and still provide a healthy, good color lawn.   Applying small amounts of water soluble fertilizer frequently through the irrigation system is the most efficient method because you apply only the amount of Nitrogen that the lawn consumed since the last irrigation cycle.  No waste.  Growers in nurseries and farms have used this method for 30 years to get the best plant per dollars spent. 

 3.  Horticultural experts tell us that grass needs about 4 pounds of Nitrogen per 1000 square feet per season.  Grass also consumes about 1" of water per week, which is about 625 gallons per 1000 square feet.   You can avoid overwatering by using a rain gauge and turning your system off when the rainfall is sufficient.  You could also do this automatically with a sensor in the soil that tells your system not to run when there already is enough moisture in the ground.

4.  You can determine how much nitrogen is in the fertilizer you are using.  If you are using 20-2-6, it contains 20% nitrogen by weight.   In a 22 pound bag this is equal to 4.4 pounds of nitrogen.  Liquid fertilizers must show on the label how many pounds of nitrogen  per gallon are in the container, usually in fine print, or you can estimate knowing it weighs about 10 pounds per gallon.   Generally speaking, a 20-x-x liquid fertilizer contains 2 pounds of nitrogen per gallon, or  5 pounds per 2.5 gallon jug.

5.  You can do the math to determine how much fertilizer per year you need on your lawn.  A 3000 square foot lawn will need 12 pounds of Nitrogen per season.  If you are using a 20% N fertilizer you need 60 pounds per season.  If you are using a 20% N liquid, you will need 6 gallons.    You can also divide this quantity to determine how many pounds (or gallons) you need per week.  If you are using a fertilizer injector, divide this number by the minutes the irrigation system runs per week.  This gives you the ounces per hour setting on the injector in order to get the right amount.

6.  If you apply 2 or 3 months worth of "slow release dry" fertilizer at one time, a large portion, (much more than you need in one week) is released to the soil as soon as you (or the clouds) apply water, and your grass gets really green quickly as the Nitrogen is consumed.   The balance (not including what can blow away, or get washed away in a heavy rainstorm) is coated with sulfur that vaporizes with heat over time.   As the sulfur vaporizes, the  nitrogen is exposed.  When water is applied this moves through the  soil to the roots.  When no moisture is applied, it vaporizes  to the atmosphere.  Fortunately it does not turn clouds green.  Then the color of your lawn fades telling you the nitrogen is gone.

 7.  If you apply a very small amount of nitrogen each time you water it moves into the soil with the water and goes directly to the roots, efficiently.  And your lawn does not "overeat" and grow too quickly, requiring more mowing.   For maximum efficiency always apply the minimum amount of nitrogen per week, not 2 months worth at one application.  This will require more labor unless you have a method to automatically dose fertilizer proportionately into a sprinkler system.

8.  When you are applying liquid fertilizer in the low dose scenario be sure to apply a uniform concentration each time.  Do not allow water into your fertilizer reservoir as that will dilute the fertilizer and  lead to an application with less Nitrogen than your calculation.