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Tests & Observation: The Dual Approach to Understanding Your Soil

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This article comes from the NOFA/Massachusetts 2018 June Issue Newsletter

By Caro Roszell, Education Events Coordinator

The date and location for this event has been changed to Monday July 23 at the UFI Headquarters, Fowler Clark Epstein Farm 487 Norfolk St Mattapan MA.

Soil testing is an important tool for anyone growing food, especially if the goal is to produce a nutrient-dense crop. But there is more to soil than its mineral content. NOFA/Mass is currently offering a series of workshops on soil testing and interpretation, which includes a lesson on both lab test interpretation and how to take your own carbon proxy tests. The series begins with Earthworms, Calcium, and Aggregates, Oh My: Soil Testing & Interpretation for Growers on June 16th at the Urban Farming Institute’s Glenway Farm in Dorchester.

The workshops will be led by the NOFA/Mass Technical Soil Support Team, Laura Davis and Caro Roszell. Laura is the owner-operator of Long Life Farm, a vegetable farm in Hopkinton MA, as well as the NOFA/Mass Board President, Certification Technical Assistance Coordinator, and Soil Technical Assistance Coordinator. Through the Soil Technical Assistance program, she advises growers on their soil fertility by interpreting soil tests and giving guidance about organically-certifiable mineral applications, quantities, and sourcing. Caro Roszell is the Soil Carbon Proxy Testing Program Coordinator and the test technician.

On June 16th, the NOFA/Mass Soil Technical Support Team will help participants understand how to read their soil tests, understand the relationship between factors like cation exchange capacity, soil organic matter, mineral levels, how to choose amendments to apply, and how to calculate how much of each amendment to put down. Participants will also learn to perform parts of the Soil Carbon Proxy Tests on their own soil, in order to put the whole biological system into context.

The purpose of the Soil Carbon Proxy tests is to assess the biological vitality of the soil, recording what is found in the soil – such as the number of earthworms, the depth of the topsoil, compaction layers present, the size and number of the aggregates, the average root depth and the growth habit of those roots. Additional data gathered from samples taken from the soil include active carbon, soil respiration, and the relative resistance of the aggregates to heavy rainfall events.

This workshop series is a part of an ongoing educational effort by NOFA/Mass to deepen general awareness and understanding of soil as a living ecosystem. Earlier this spring, in the final session of Soil Science for Farmers and Gardeners, workshop participants assembled at Noah Kellerman’s Alprilla Farm in Essex, MA to learn about soil tests. In the 7-week class Noah covered both traditional lab soil tests as well as a portion of the Carbon Proxy Tests.

In the course of the class, Noah explained that, while soil mineral testing is important, “you can really learn a lot by taking a spadeful of soil and observing it.” At NOFA/Mass, we take the approach that mineral and biological tests can inform each other, and Noah’s comment really sums up this approach. I asked him to expand on this thought, and have paraphrased his comments below.

If our goal is to grow plants, and plants are biological organisms, then it follows that we should observe the biological system that supports those plants. Lab soil tests are excellent tools, but they are not the only tool in the toolbox. You have to check your work – meaning observe your plants, look for signs of deficiency, and consider the larger context.

If I’m approaching a field I’ve never worked with before, the first thing I’d do is look at what’s growing there. If there is a cover crop and there’s rye and vetch, how does the rye look and how does the vetch look? Also, pick up the soil. Smell it. If it smells bad, it’s anaerobic. But anaerobic soils, when tested by a lab, will show minerals that are not available when the soil dries out. If it’s a field you have been working, look to see if the previous year’s crop residue is still there. That can tell you that your biology is fried from tillage or chemical applications. Look at the crumb structure and whether there are earthworms.

One should always account for the level of biological activity of the soil when interpreting a soil mineral test. Lab soil tests are geared toward more conventional crop production, and make recommendations assuming an inert soil. A biologically active soil may not need the full amount of N-P-K that the lab test might suggest. But a more biologically inactive soil is likelier to need closer to the recommended levels.

Participants attending any of the Earthworms, Calcium, and Aggregates, Oh My: Soil Testing & Interpretation for Growers workshops can get a soil test interpretation from NOFA/Mass as a part of the cost of their registration fee, as long as they can procure a soil test from Logan Labs before the date of the workshop. Also available at the workshops will be pre-assembled “mini kits” for taking some of the carbon proxy tests on your own fields or gardens, with a manual to guide you, for sale at cost-of-materials.

 

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