Taking Soil Samples for Soil Test

Since I posted my blog on interpreting soil sample results, several people have asked me about collecting soil samples. 

Collecting soil samples for your soil test is easy. Here is how I do it.

Make sure that you follow the directions exactly included with either type of test kits as it will affect the results of the test. Always make sure to use clean tools and bucket.

When you take the sample, make sure the soil is not too wet from any recent rain or prolonged watering. To get the best results take the sample before any fertilizer has been applied or at least not recently applied.

To begin you will need a clean pail or mixing container. Unless it is brand new then make sure that is well cleaned (rinsed out & dry). By not washing the pail out carefully any remnants of prior use could register in the soil test.

Use a shovel to dig a small hole 3 to 6 inches deep. With the shovel, after the hole is dug, take a sample of the turf and soil plug from top to bottom. I shoot for a sample that is about 1" down from green part of the grass (where the dirt is). That is the sample you will use for the test. Once you have the sample, place it into the pail.

Taking a soil sample from the 3-6" depth of a soil plug

To make a composite sample that is representative of the whole yard (or area you want to have analyzed), take samples from various parts of the yard. You want a total of 30 samples (this year I collected 15 from front and 15 from rear). I use my rake (shown in the photo above on the left) to take samples every 1.5 meters in a crisscross pattern. From each area try to put approximately the same amount of soil into the bucket.

Avoid areas that are near the drip line (especially if you have lead-based paint). If the soil is not dry, then put the pail aside in a sheltered, dry location and let the soil dry overnight.

Boxing up my dry mixed soil sample

Combine the soil thoroughly in the pail and remove the amount the lab requires for the test. Put the sample in the container approved for the test and mail it as directed or return it to the testing office. By mixing the soil you will be providing a typical sample. This way the sample is representative of the areas sampled and the corrective measures recommended (e.g., fertilizer) can be done evenly over all those areas the yard.

Cheers,

Mark

Soil Testing: results and interpretation

The image below shows the results of my spring 2012 soil test for my lawn areas. This was the $33 test from University of Maine Cooperative Extension. While the test may seem a bit expensive, the information provided is well worth the price.

2012 Soil Test Results

Previous years' tests had suggested I needed to add more compost (hence my earlier blog showing overspreading compost), and this test shows that I can still use a bit more compost. 


My calcium and pH levels are shown as above optimal, but the levels shown better suit my grass strain (see photo below). I achieved these higher levels through the addition of gypsum (gypsum raises pH, makes soil nitrogen more available, and prevents compaction and salt damage) over a four-year period (I used approximately 80 pounds per year on my lawn area). I will have a blog later this month devoted entirely to gypsum.

Photo of lawn-- look at that beautiful clover!

Interpretation of Soil Test Results


Macronutrients (N-P-K)
 These are all in the reasonable range. Some may say that my nitrogen level is low. I would not argue that the reading is low, but I expected as much. This is before any work on my lawn and my addition of compost and vermicompost tea will get the microorganisms fired up to start making nitrogen available. Also, I have clover in my lawn to pull nitrogen out of the air and fix it in the soil. I will not “fertilize” my lawn with nitrogen based fertilizer because it is not really needed. If you read the fine print, I would use 2 pounds of nitrogen per 1000 square feet, but only ½ that in late August (because I mulch my clippings) and because of organic program I would use only ½ of that. That takes me to ¼ pound of nitrogen per 1000 square feet. My compost overspreading this spring should supply my needed nitrogen as well as any sulfur and potash.


Soil Life (Microorganisms)
My microbial biomass index is 44ppm, which is on a 1-100 scale. I am trying to get closer to 60ppm (optimal range). As I add more compost to the lawn (recall that I took these samples before my spring 2012 compost overspreading) the level will increase.


Micronutrients
The decrease in micronutrient availability to plants as pH increases is not a great concern to me because it is a balancing act (given my increased pH and additions of humus-rich compost to the yard). Also, I plan to supplement my vermicompost tea with sea weed this year to boost the level of micronutrients that are available to the grass plants.


Long View
My long-term goal is to have no external inputs to my lawn (just aeration, overseeding as needed, and vermicompost tea), so everything I do is a step in that direction. It is important to remember that small steps are the best approach. Make sure your additions are based on the recommendations in the soil test. You don’t want to overshoot—that would waste both money and time. Remember that I am mulching my lawn clippings, so there is no net loss of anything (macro or micronutrients).


Early in your organic switch, you should test your soil annually to check your additions. After that you can back off to once every three to five years-- preventive lawn maintenance. If lawn problems develop more frequent testing may be necessary. 

Organic Lawn Care — Spring

By request, I am compiling my organic lawn care recommendations in one place and starting a WormMainea YouTube channel.


In this video I show how to core aerate with the Yard Butler*

In this video I demonstrate overspreading compost

I also took a soil sample from the yard to see whether I am getting close to my target organic matter level and whether need to do anything else (calcium, etc.). I took a composite sample from 15 areas (5 front yard, 5 side yard, and 5 back yard). These approximately equal small samples were mixed in my soil tub and then placed in the box.

Collecting a soil sample for the University of Maine Cooperative Extension Soil Test

Here are links to some of my earlier blogs related to lawn care

http://www.wormmainea.blogspot.com/2010/04/natural-lawn-care-preparing-and-timing.html

http://www.wormmainea.blogspot.com/2011/04/integrated-pest-management.html

http://www.wormmainea.blogspot.com/2010/09/how-well-does-organic-lawn-care-work.html

http://www.wormmainea.blogspot.com/2010/04/thoughts-on-weeds.html


*The Yard Butler D-6C Core Lawn Aerator is great for established lawns or lawns where a lot of activity takes place. Core aeration reduces compaction and thatch to let air, water and fertilizer down to the root zone. Core aeration also stimulates root growth by “pruning” the roots and deposits valuable micro-organisms on the lawn surface. I find this tool a lot easier to use than the gas-powered beast I rented from Home Depot a few years ago. And, because I have it available, I can use it to aerate compacted areas when someone drives on the lawn.