At this point I pretty committed to centipede. Honestly, the front yard looks really good in the summer time and justifying the time and expense of killing it is a tough sell. Backyard struggles in spots around trees and high traffic places.
Centipede is the dominate grass in my area. If you move into a production builder type neighborhood here 95% of the time its centipede. If you go to Lowes/Home Depot to get sod that is what they have.
I wasn't being judgmental. The conditions in which Centipede thrives are so different from those of most other grasses, that I wanted to know if you had any future plans that would be contrary to my suggestions.
I did a little reading on Centipede and to my surprise, I was pretty accurate with my initial recollections. So, I'll keep those in mind.
To start, I have a thread in the FAQs section that has the sufficiency ranges for nutrient levels based on the Mehlich 1 test. You may want to compare your test values to those just to get an idea of where your levels are. Please note, those values are not tailored to Centipede and may or may not have any useful relationship for targeting "desired" levels of nutrients. For know, just use it as a resource to get your bearings. It is for ppm values. Dividing your soil test lbs/acre values by 2 will give you your soils values in ppm. BTW, the images of your test are blurry and hard to read. When I click on them I get some kind of error message page.
When every source I came across recommends low soil levels of P and a pH <6, one can be pretty confident that there is reliable validity to those recommendations for Centipede grass.
Your observations reflect this. The lawn with the lower pH and P levels is doing better than the lawn in the soil with the higher pH and P.
Consequently, I would suggest you be so guided in making adjustments to your soil.
First, as pH is so important to the performance and health of Centipede, I suggest you consider lowering it.
Attempting to adjust soil with a pH greater than 7.2 is pretty much a "fool's errand", like trying to desalinate the ocean. A field study was done in the early 2000's to test the effect of sulfur applied to a heavy loam soil with a pH of 8. The equivalent of 225lbs/M (they applied 10,000 lbs per acre) of sulfur was incorporated into the soil. Soil pH the following year was 7.4. In years 3,4 and 5 it was 7.6 and for the next 5 years it held steady at 7.8. That's a lot of sulfur for a permanent pH reduction of only 0.2 pH, a pH drop that would have no significant improvement in plant health or crop production.
However, reducing pH in soils with a pH of 7 or lower is realistically doable and attainable. Based on a loam soil, it is consistently roughly calculated that 2#/M of elemental sulfur will lower pH by 0.1. 90% ES is relatively cheap in 50# bagsNo more than 5#/M should be applied at any one time and no more than 10#/M should be applied in a calendar year. Synthetic fertilizers have a greater acidifying affect than organic fertilizers. 2.8 lbs/M of ammonium sulfate (21-0-0) has the same effect as 1# of sulfur. A lot of variables come into play: CEC,, soil texture, climate and watering practices, but IMO, you could apply 4#/M of elemental sulfur ASAP, use ammonium sulfate as your fertilizer and apply another 4#/M of elemental sulfur at the end of Summer. Theoretically, that would lower the pH 6 soil to around 5.5 and the pH 6.8 soil to about 6.3, only a test next year will tell.
I would suggest that you avoid any additions of P this year. As Milorganite contains significant amounts of P, I would suggest you not use it.
If you decide to use ammonium sulfate as your fertilizer, and can't find fertilizer containing it that also contains a significant portion of potassium (K), you will want to source potassium sulfate (SOP) and apply 3# of K/M. That would be 6# of the SOP product broken up into three or more evenly spaced application through the growing season for the front lawn and 2# of K/M in the back yard. That would be 4# of SOP product and could be applied at 2# of SOP/M at the same time as your N feedings. Dividing up the SOP so that it is more heavy in the Fall would be advantageous for Centipede.
Any chlorosis issues can be resolved with spray applications of Iron sulfate (2 oz/4 gallon of water).
I would suggest that you invest in 5 gallon buckets with lids to store the ES and SOP to keep them dry as 50# will last you a couple of years on a 3000 sq ft lawn.
Hope that helps. Sorry for getting so specific with my suggestions. As always, it's your lawn and decision.
