Improving acidic soil for St. Augustine grass growth

Asked March 13, 2015, 10:08 AM EDT

I live in northwest of Houston. I did soil test and results indicate need for nitrate (0.7 - 0.9 lbs/1000 sqft), potassium (0.6 - 1.8 lbs/1000 sqft), little bit of magnesium (0.25 - 0.5 lbs/1000 sqft). But most importantly it indicates that soil is very acidic, ranging from 4.2 to 5.1 PH. Report suggests need for limestone (40-80 lbs/1000sqft).

  • How to raise PH of the soil?
  • What type of lime do I add? Is one kind of lime treatment better than other?
  • What is the best method of adding lime? How often do I add lime to soil?
  • Is there any kind of fertilizer that I should or should not use if I am adding lime?
  • Report does not suggest need for phosphorous. But most fertilizers include it. Will it hurt if I add phosphorous when not needed?


Harris County Texas

7 Responses

There are 2 forms of limestone on the market calcitic and dolomitic. Calcitic or agricultural limestone is calcium carbonate and dolomitic is a combination of calcium carbonate and magnesium carbonate. In your case using the dolomitic form will help improve your magnesium deficiency. These 2 forms of limestone are easy to apply, but they work slowly in raising the pH. They can be applied any time during the year. I would recommend 3-4 applications over a 1-2 year period in order allow the lime to work into the soil.

If you are looking to add the low range of the recommendation of 40lbs/ft2 an option would be 4 applications at 10lbs/ft2 to reach the recommended rate (spring/fall applications).

At this time I would not worry about additional fertilizer, improving the pH of your soil will improve the availability of other nutrients to the plant.

The Turf Answers 4 You tab has additional information on lawn care at the aggie turf site.

Thanks for the question.

Thanks Paul,

When I add lime, do I just spread it on top of existing lawn or do I have to work it into the soil by mixing it with lawn/top soil?

You mention that lime takes time to work into the soil. If I add lime now, will I see some/partial sign of improvements by end of summer?

If you have a lawn spreader, either drop or rotary that will make it easier to apply. The bag will have recommended settings for the type of spreader.

If we get adequate rain that will help the lime work its way into the soil. If you make 2 applications this year, take another soil sample a year from now and see if the pH has moved up for you. There are faster acting forms of lime but you would need to work with a lawn maintenance company. If they are applied incorrectly, the grass can be burnt and damaged.

Thanks Paul. Appreciate your time.

Sorry for asking too many questions :-)

I went to Home depot and they suggested using Pennington Fast Acting Lime Plus AST. The bag does not indicate dolomitic, so I assume it is calcitic. Not sure.

Is this product a good alternative? I am asking because you mentioned that I should work with lawn maintenance company to use fast acting form of lime.

This will be fine. It is pelletized and will be easier to handle.

Please follow label instructions.

Good luck

Appreciate it Paul. Have a wonderful day!