Monday, October 18, 2010

Get a Soil Test Dammit!

We knew we had nutrient deficiencies. We could see the symptoms in the plants. Our production was good in some beds but not in others. I had read many articles that spoke of the need for large scale re-mineralization of soils. We knew we could increase our production with the addition of needed nutrients in the correct amounts. A friend told me he used International Ag Labs to test his soil. He liked that they emphasized biological farming and growing nutrient dense food. We sent them a soil sample from our back field.
We were correct in our assumption that we had deficiencies. We followed their recommendations and had a custom blend of soil amendments prepared for us and applied it at the recommended rate. This was last spring. The results were quite obvious as the crops started to grow. Throughout the summer season we began to notice we had less pressure from disease and insects than in the previous year. The plants looked super healthy; dark green leaves and thick strong stems.

When we first started the garden we prepared the front field differently than we did the back field and we got better production. We used more compost initially. After we determined we had a deficiency of magnesium we applied dolomitic limestone to add both calcium and magnesium. We saw some improvement but we felt were not getting maximum production in that field either. We sent in a soil sample from the front field about a month ago. As you can see the results are quite different than those we got in the back field.

Notice in particular that test shows excessive levels of phosphorus and potassium. The folks at International Ag labs have found that excessive use of manure based compost can cause this. We believe that is why we our levels are excessive. We applied a whole lot of compost that year. Note that they recommend not applying compost or manure of grass clipping or wood chips until the excess has been used up by the plants.

Notice all the notes i wrote on the pages of the test results. They are answers to the many questions i had about the test and recommendations. I love that I can call Jon Franks and he will patiently explain what the meaning of the test results are and why they made the recommendations they did. If you look at the test for the back field, it shows that the levels of copper and manganese are very high yet they recommend adding both to the soil. I asked Jon why that was. He said that the desired level for plants is lower that that required by the human body for maximum health so they recommend higher amounts in the soil to boost the nutrient density of the plants. Our goal is to grow the best food we can for ourselves and for our customers so we followed their recommendations.

People regularly ask me in my workshops and lectures what brand organic fertilizer i recommend. My answer now is always that i don't recommend any particular brand. I explain to them that without a soil test you cannot know what nutrients your soil needs. Plants need different nutrients in the proper ratios. The calcium to magnesium ratio should be 7 to 1. The phosphorus to potassium ratio should be 1 to 1. If you are continually applying a balanced fertilizer without knowing what the ratios are in your soil you can throw the balance out of whack. The result is that the uptake of other nutrients is blocked. You might be creating excesses of certain nutrients with the same results. That is the situation we see in our front field.

"But it is expensive" is the comeback i often hear. A soil test can actually save you money. Once you get the results, you only need to purchase and apply the nutrients your soil needs. And I can testify that, assuming your soil food web is healthy, your production will go up markedly. In 4 months we have produced as much food as we did all last year. I a couple of weeks we will have harvested a ton, yes 2000 lbs. of food since the beginning of June. On 1/8th of an acre.

Get a soil test dammit!

p.s. if you want to study these results more closely you can find them here on


helenw said...

LOL - I actually did last week after your last post. Just a County Extension test tho-

duane marcus Facebook me! said...

Great Helen. Georgia Organics has been trying to convince the soils lab at UGA to provide organic recommendations. Hopefully they will be doing that soon.

helenw said...

I was expecting to have to translate my results to organic/acceptable to me recommendations. Got my results and all my nutrients are off the charts - so no deficiencies - but I think I'm going to get the kind of test you did to check proportions. I suspect that my soil is like your super-compost-enriched soil.

duane marcus Facebook me! said...

Great news Helen.