Turf Tips
03/07/2008

Choose Preemergence herbicides with as Little N as Possible

If a preemergence herbicide is justified on your lawn to control crabgrass now, most of those are available combined with fertilizer and you are forced to apply a fertilizer now. Look for a product with low nitrogen and be sure the majority of the nitrogen is a slow release N. Slow release sources include sulfur- or polymer-coated urea, urea formaldehyde, methylenediurea, dimethylenetriurea, or natural organic nitrogen. These are listed on the label as “slowly water soluble” or “water insoluble. Nitrogen rates at this time of the year should be as low as possible and never over 0.75 lbs N/1000 sq ft. Applying too much fertilizer now will encourage too much growth and could lead to problems later this summer such as poor root growth and disease. Additionally, since spring rains play havoc with mowing schedules, nitrogen fertilization can further complicate your mowing schedule by causing grass plants to grow too fast.  There are hundreds of choices available for preemergence herbicide/fertilizer combinations and I have seen products with N as low as 0% to 5%.

Zac Reicher, Professor/Turfgrass Extension Specialist