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  • Writer's pictureJason Boorn

A Guide to Watering Programs

I wanted to discuss watering programs and why they are so important.  This will be a rather long post, but I believe everyone would benefit tremendously from reading it, as client participation in a good weed control and fertilization program is key to having the best possible results.  I will start with how a watering program affects pre-emergent control of weeds.  

Pre-emergent chemicals do not prevent weed seeds from germinating, which is a common misconception.  They actually kill the plant as soon as it begins to break through the seed coat.  Because most seeds are in the top 1-2 inches of your soil, this is the location we want pre-emergent chemicals to reside. This is the primary reason we use a split application approach to our pre-emergent treatments, so we can ensure pre-emergent resides in the top layer of soil for the duration of each treatment period. 

The first step is getting the pre-emergent into the soil profile.  Although some of the chemical enters the soil profile upon application, much remains on top of the soil.  The longer it remains in this location, the more time the sun and weather are able to deteriorate the chemicals. To prevent this deterioration, water each application in for 5-10 per zone within 24-48 hours to ensure the highest percentage of chemicals enter the soil profile.  A good rainfall will also suffice. Failure to water in a pre-emergent application could lead to very little control of weed germination, especially as time goes on, and what chemical did penetrate the soil will dilute and spread downward, deeper into the soil profile.

The next step is appropriate watering.  Warm season lawns (bermuda, zoysia, centipede, etc.) require roughly 1.5 inches of water per week.  The best way to provide this is watering deeply, infrequently.  This encourages deep root growth and prevents issues with perennial weeds (your lawn is a perennial plant) such as yellow nutsedge, which prefer soils that are often damp.  It also helps your lawn better handle heat and drought, keeping your lawn greener, longer, rather than yellowing in August when temperatures are regularly around 100 degrees with little rain.  Watering daily or every other day encourages this type of plant development.  

Rain supplements your watering program, something many people do not take into account.  We recommend watering 2x per week at ½ inch of water per zone.  You can use a rain gauge or tuna can to determine whether your zones are watering appropriately.  When there is no rain for a period of two weeks, increase your watering time to account for the additional water requirement, but do not add watering days.  An easy method of accomplishing this is to divide your current watering time by 2, and add that time to your current watering schedule.  If additional rain provides more than the ½ in you want per week, reduce watering times or turn off the system.  The goal is to provide 1.5 inches of water per week, no more and no less.

We all know what happens when you water too little, but why is watering too much a problem?  There are several reasons, but we will cover two.  First, heat and water are breeding grounds for fungal growth.  The more often your lawn is wet, the more likely fungal growth may occur.  Curative fungicides are expensive, so ensuring your top layer of soil remains dry for as long as possible is the best approach to avoiding fungal damage to your lawn.  Second, the more water your lawn absorbs, the more diluted and further down in the soil profile your pre-emergent goes.  This means the pre-emergent you spent hard earned money on, will be less effective.  Neither you or your contractor (us) wants that.

Something to consider when setting up your program is runoff due to clay soil.  Oftentimes, it may take 30+ minutes to get ½ inch of water on your lawn in a particular zone.  The best way to reduce runoff and ensure your lawn is getting the water it needs is to water in cycles.  For example, if you require 30 minutes in a particular zone to water ½ inch, set that watering program up for two cycles, at 15 minutes each.  Since most have at least five zones, that will give that zone about an hour to absorb the initial ¼ of water before being watered again, helping reduce runoff.  When there are periods of no rain, simply add a third cycle to make up the additional ¼ inch of required water.

If you made it this far, thanks!  Lawn treatment programs really do require client participation to achieve the best lawn possible, and taking the time to set up an appropriate watering schedule and ensuring all pre-emergent treatments are watered-in, will go a long way in ensuring optimal results. Provided weekly/biweekly maintenance is being performed, if you follow this guide, you are well on your way to a beautifully green, lush, weed free lawn! 

Finally, as a side note, perennial plants are not prevented by pre-emergent, they remain year after year as adult plants, generally going into a period of dormancy when conditions are not conducive for growth.  Annual plants such as crabgrass, are what we are targeting with pre-emergent treatments.

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