Wednesday, August 12, 2015

Soil Testing

I test my soil with plants.

Soil scientists have learned to test soils for various nutrients. This is done by using strong chemicals to strip off the nutrients or react with the nutrients in the soil and establish a quantitative measurement. I'm always a little skeptical that the strong chemical processes can correctly detect nutrients available to the plants in a organic system that uses biological processes to make nutrients available.

I have never done any soil testing on our farm. Instead I observe the plants. For example...

The first year we were at our farm we noticed the tomatoes and peppers had significant blossom end rot. This indicates the plants are stressed. This is typically an indication of a calcium deficiency coupled with water stress at the time when the fruit is developing. So we limed the farm in two applications over the first two years. No more blossom end rot.

I also noticed that one field had mostly broad leaf weeds and another had mostly foxtail. The foxtail shows up in a poorly aerated and acidic soil. The lime would help with the pH bringing it more to neutral and flocculate the clay particles in the soil, helping the soil be less compact. Organic matter also would loosen and aerate the soil. I grew a winter rye and vetch cover crop in the fall/spring of the third year we farmed this field and that did the trick. I estimated we got about 20 tons of organic matter per acre with this treatment. It was so massive I had a farmer chop the field and I composted it. I'm still using this compost many years later.

The broad leaf weeds in the other field were mostly rag weed. The liming process shifted these weeds to other broad leaf species. We typically till between the rows and pull the weeds in the row. Nature doesn't like bare soil, so we will get a second growth of weeds later in the season and I often just let them grow as a cover crop and till them before they go to seed if that is an issue.

There are books written about what different species will show up depending on what is going on with your soils. Mostly these are considered weeds, but in nature they are there to heal the soil and compensate for nutrient deficiencies. Bringing the soil back into balance so more desirable species can thrive.

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