Testing Our Soil - pH, nitrogen, phosphorus, and potassium

I'm doing a little Chemistry today! 

We were able to obtain a soil testing kit from an industrial supply store in our area. You can find similar kits on Amazon: http://www.amazon.com/Luster-Leaf-Rapitest-Tester-1609CS/dp/B0019AI7PU/ref=sr_1_6?ie=UTF8&qid=1393708580&sr=8-6&keywords=soil+testing+kit 
Home Depot, Lowe's, and local gardening supply stores will have them as well.

The soil sample I took was actually from a fresh gopher hole in the yard (the instructions say to get the soil sample from 6-8 inches underground) We WILL be getting rid of the gopher as soon as possible, because I know that he/she/they will interfere with our gardening endeavors!

This sample was taken before adding anything - no manure, wood ash, or compost.

The process of testing the soil was fairly straightforward - I really enjoyed doing it (I was a Chemistry major in College).
The kit came with:

• -Tubes
• -Tablets
• -Color chart

I provided

• -A soil sample
• -A Styrofoam cup
• -Water

The kit said to dry the soil sample for an hour. Humidity here is about 14% today (and is always quite low because we are in Southeast New Mexico), so I skipped this step.



The first test was the pH test. The soil was directly mixed with water and the testing tablet.

Our soil has a pH of about 7.0. This is not too bad. We do need to get it acidified a little, but it is not as alkaline as I thought it would be.

The next step was the nitrogen test. I mixed the soil with a few tablespoons of water and a special tablet. It was stirred in a Styrofoam cup and then the soil was allowed to settle out. The water from this mixture was then placed in the tube and mixed with the nitrogen testing tablet. Then the tube sat for about 5 minutes. 

It appears that we have very low nitrogen in our soil. Adding manure should help with that.

I did the phosphorus test next. In this test, I added only a 1/4 teaspoon of the soil water from the Styrofoam cup, then the test tube was filled to the top with pure water. After adding the tablet and shaking, the tube sat for 5 minutes.

It seems that we have fairly low phosphorus in our soil.

The next test was for potassium. The tube was filled to the top with soil water from the Styrofoam cup. The tablet was added and the tube was shaken. I did not have to wait for the results of this test, the solution turned cloudy right away.

The tube was placed in front of the row of black marks on the color sheet for comparison. Since the solution was extremely cloudy (not much black showed through) we have high levels of potassium in our soil.



So our sandy soil is essentially neutral, low in nitrogen, low in phosphorus, and high in potassium. We will over the next few weeks need to:

• Acidify the soil by adding manure
• Increase the amount of nitrogen in the soil by adding manure
• Increase the phosphorus in the soil by adding a fertilizer mix or bone meal
• Think about not adding wood ash to the garden (it is very high in potassium)

Also, I will probably look into having our soil tested by the local county extension office and I will see what they recommend to add/not add.