Sunday, March 11, 2012

Soil Test for the New Garden(s)

Just got my soil test results for the new place. Looks like I'm going to need to do some work. I took a sample from the area in the back I want to plant a garden, and the area in the front where I might also plant a garden. Both areas are, in general, not as good as my former garden, and the front here is in worse shape than the back, which doesn't surprise me. It looks like the area in the back had been a garden before, and has probably been amended in the past. The area in the front, on the other hand, if it was used for anything by previous residents, it was for parking cars if the driveway was full. I got the same test that I got for the last garden, which tests the NPK, pH, micronutrients, and organic matter content. I noticed they have added some more tests I could do, like seeing the % of sand, silt, and clay, but I decided this test covered what I mostly care about.

My previous garden had a pH of 7.6, which is only slightly alkaline. It was low in nitrate, with 5 ppm, slightly low in sulfur, with 11 ppm, and organic matter was pretty high at 6.34%. And this was in a patch that I hadn't added anything to. All the other nutrients were above the critical level (CL) which means I had enough of them.

The patch in the back, which is now all rototilled up, is not as good as my previous garden, but not too bad.

pH = 8.1
Nitrate = 3 ppm
Organic Matter = 5.14%

So the pH is even higher, the nitrogen is lower, and the organic matter is lower (but still pretty high, because from what I looked up, anything above 5% is good). I wonder if adding a load of composted manure could help with all those things. All the other nutrients are above the CL, so they're fine.

The front yard is in the worst shape. The pH is even higher, the nitrate is hardly detectable, the organic matter is even lower, and it's also deficient in phosphorus. All the other nutrients are fine.

pH = 8.2
Nitrate = 1 ppm
Phosphorus = 34 ppm (CL = 50)
Organic Matter = 3.33%

I'm going to have to add a bunch of manure or compost or something, and I'll also have to find a source of phosphorus to add as well. When I looked up what to add for phosphorus, I got bone meal and rock phosphate. I'd rather use bone meal, since it's a meat by-product, instead of something that has to be mined, like rock phosphate. Don't know how much phosphorus manure or compost would provide.

Texas A&M also lists the NPK requirements for the more common vegetable crops, which is helpful because the soil test just gives a general critical level for vegetables. I was thinking of planting squash in the front yard for this first year, and letting the vines roam around freely in that big space. It says that squash needs 20 ppm of nitrate, 45 ppm of phosphorus, and 125 ppm of potassium, so I'll have to give them both nitrogen and potassium to make them happy.

I guess the good news is that phosphorus stays in soil much longer than nitrogen, so once I build up my level, I shouldn't have to add more again for a long time.


  1. Used coffee grounds are acidic, right? Maybe not in the quantity you need, but you can often get them free from coffee shops.

  2. Coffee grounds are also high in nitrogen, but I'd need to go to a coffee shop to get the quantity I need.