Container gardening with bagged soil is much easier than growing in Texas gumbo, but for the size of our garden importing soil is too expensive. So we did the next best thing: we got our soil analyzed to see what we need to add.  (Note for lazy people: skip to the end for the cliff notes version of this post)

Remember the analogy “if you give a man a fish he will eat for a day; if you teach a man to fish he will eat for the rest of his life”? When you fertilize the soil, you are just feeding the plants.  If you add the right concoction of organic materials, compost, and microorganisms, it builds up the soil ecosystem and then the soil takes care of itself.  So before we plant crops, we actually need to “brew” the soil so it will continue making nutrients for the plants.  Having the soil work for me will allow me to be lazy later 🙂

There are two places in Texas that will analyze soil:

Texas Soil Lab

And Texas A&M

I went with the Aggies since the tests were a little cheaper and more comprehensive for the price.  All I had to do was dig a hole about 6″ deep and take soil samples from 6 to 8 spots in the backyard.

We did the Routine + Micro + Boron + Organic matter test for $44.00 because we’re growing fruit trees so we wanted to get the amount of boron analyzed.  I also asked them to recommend fertilizer amounts for both the fruit trees and vegetable garden.

I visually inspected the soil and discovered we totally lucked out…it’s not the Texas Gumbo soil that most folks in North Texas are cursed with. We have more of a reddish sandy loam, at least for the first 12″ and then it turns into red clay. I’m not sure if the builder imported dirt and sand to level the property or if it’s naturally occurring, but hey I’m not complaining.

We got the results back via snail mail in about two weeks.

The soil is slightly acidic at a pH of 6.4. Remember your Chemistry? The lower the pH means more acidic, the higher the pH is more basic (also called alkaline) with pH of 7 being neutral. So pH 6.4 is good; lots of edible plants won’t grow in alkaline soil.  Most soil around Dallas is alkaline.

In addition to analysis, they tell you what you need to add to your soil to bring it up to the “critical level” of nutrients. Since we’re not adding any synthetic fertilizers, I had to calculate how much of the organic amendments to add…which gave me more flashbacks to Jr. High School math class.

OK students, let’s calculate the amount of Nitrogen, Phosphorous, and Potassium to add to the soil for the vegetable garden.  On any bag of fertilizer, organic or synthetic, you will see three numbers. These correspond to the percent of N, P, and K in the fertilizer.  So for a bag of fertilizer that says 5-8-4 you would have 5% N, 8% P, and 4% K per weight.

For those of you who love math, here’s the equation: A&M recommends 1.2 lbs Nitrogen, 3.3 lbs Phosphorous, and 1.0 lbs Potassium per 1000 sq ft. The best organic fertilizers are Blood meal for Nitrogen, Bone meal for Phospohrous, and Green Sand for Potassium.  Apparently dogs and other animals will dig up the blood/bone meal so if you have canines or raccoons you will have to till it in the soil really well, or mix it in with some manure and put some rocks around it to discourage digging.  The closest gardening store, Marshall Grain Co., sells these organic fertilizers:

Blood Meal 12-0-0               2.7 lbs for $8.99

Bone meal 0-10-0                4 lbs for $5.99

Green Sand 0-0-3                6 lbs for $5.99

How much of each would you need to mix to cover a garden plot of 1000 sq ft, and how much would it cost?

Luckily this isn’t 7th grade math class…in the real world you can google anything and A&M just happens to have an online calculator that does all this for you [insert evil laugh]:

http://soiltesting.tamu.edu/webpages/calculator.html

The online number crunching revealed that we need the following mix for 1000 sq ft:

10 lbs of 12-0-0 blood meal

33 lbs of 0-10-0 bone meal

33 lbs of 0-0-3 green sand

For a 4′ x 20′ plot we would need 0.8 lbs blood, 2.6 lbs bone, and 2.6 lbs green sand.  DONE!   A+

The soil analysis also showed our soil is low in Boron but it didn’t give an amendment recommendation. Boron is required for good fruit tree development and I even paid extra for the analysis. So I called the soil lab and asked what’s up. Boron is a trace mineral so to bring our soil up to snuff it would barely take 0.02 lbs / 1000 sq ft. So the best way to add Boron it is simply to mix in compost. So save your money folks and don’t get the Boron analysis, they will just tell you to add compost.  Same with the sulfur…our soil is already acidic and sulfur will make the soil more acidic which we don’t want.  So there’s no point in adding these separately to the soil amendments since compost will already have these trace minerals.  The limestone recommendation is just to make the soil more alkaline for the fruit trees.

We have 1.97% organic matter in our soil…whoop dee doo.  This number doesn’t really give any useful information and I’ll be adding some compost anyways.  I should have just got the routine + micro analysis for the soil for $17.

 

So here’s the Cliff Notes version of this post:

1) Measure the size of your garden and calculate the area
2) Get your soil analyzed HERE or HERE
3) Call your flavorite gardening store to find out how much N P and K are in their blood meal, bone meal, and green sand
4) Use THIS LINK to calculate the amount of organic fertilizer you need to add to your soil.

Stay tuned for the next post where I will show you how I mixed in the organic fertilizer, compost, and microorganisms to the soil and prepared the lawn for transformation!