Remineralizing Our Soil – Part 1
Early this past fall while researching soil test interpretation, I came across a very interesting methodology for balancing soil minerals called The Ideal Soil. I knew of the importance of certain minerals in the soil – tidbits like “lack of calcium can cause end rot in peppers and tomatoes.” But I wanted to gain a much more thorough understanding of soil minerals because despite our additions of compost and using mulches to keep the soil surface covered whenever possible, it seemed like our soil just wasn’t where it needed to be. It dried out very quickly, was lacking in the ability to form clumps, the compost we added didn’t seem to be getting properly integrated into the soil, and we were having crop failures in some of our beds. As I read over this new information, it was like a light bulb going off in my head as I connected specific mineral deficiencies with the problems we were experiencing.
This methodology for balancing soil minerals is well explained in The Ideal Soil v2.0: A Handbook for the New Agriculture by Michael Astera with Agricola. I recommend visiting soilminerals.com and reading Chapter 1 and Chapter 2 of the handbook. Chapter 1 will give you an interesting background on Dr. William Albrecht, a scientist who developed the methodology in the 20’s – 40’s. Unfortunately his team’s work was suppressed as the NPK-focused chemical warfare style of agriculture won out. Chapter 2 explains the theory behind the methodology. The two main premises of the theory are:
1) Each soil has a unique cation exchange capacity, or ability to hold nutrients. Higher clay soils have a higher cation exchange capacity (CEC) because clay particles are negatively charged and therefore bind to positively charged ions like calcium and magnesium. Cation exchange capacity can be increased by adding materials such as humate ores and biochar and/or by increasing humus content through the addition of organic matter. However, these attempts will be much more successful if the proper balance of minerals is in place.
2) When that CEC is 100% saturated, it means that all of its negative charges are associated with a positive ion. Hydrogen (H+) and Aluminum (Al3+) are two of the positive ions in soil, but neither of them are plant nutrients and they both increase the acidity of the soil, lowering the pH. Calcium (Ca2+), Magnesium (Mg2+), Potassium (K+), and Sodium (Na+) are plant nutrients and are considered the alkaline cations because they make the soil more basic, increasing the pH. Albrecht found that there was an ideal balance between these four major cations that when achieved resulted in a soil with a balanced pH, good water retention, good texture, and active soil life that turns organic matter into humus, along with very healthy plant growth with fewer diseases and pests and a better nutritional profile in resulting produce. This ideal balance is about 65% Calcium, 15% Magnesium, 4% Potassium, and 1-5% Sodium.
For a specific soil, once the cation exchange capacity is measured, some relatively simple math can be used to calculate the ideal level of the alkaline cations, the anions phosphorous and sulfur, and the minor elements boron, iron, manganese, copper, and zinc. Even though they generally are not measured in soil tests, you can also add materials to the soil for trace minerals which are needed in very small amounts such as iodine, cobalt, and selenium. If you are a science and math oriented person, I strongly encourage you to buy the Ideal Soil Handbook and learn how to do the calculations yourself. If not, the folks at soilminerals.com offer a testing interpretation service which is described on their website.
So let’s look at some soil test results and compare with the “symptoms” we were seeing in our garden. In order to keep my calculations organized I created a spreadsheet that you’ll see below. The results column contains the values we got back from Logan Labs. The Ideal Value column contains either a given or calculated ideal value (you’ll need the handbook to calculate these). The deficit column shows the difference between the ideal value and the results. The recommendation column shows whether we need to then add the mineral. If something is too high, we assume it will level out on its own as deficient minerals are added.
|Soil Component||Ideal Value||Results||Deficit (ppm)||Recommendation|
|Soil pH||6.4 – 6.5||6.3||OK|
|OM (%)||2 – 10||12.88||Should level out|
|S (ppm)||168.95||23||145.95||Add 145.95 ppm S|
|P (ppm)||338||233.64||104.26||Add 104.26 ppm P|
|Ca (ppm)||2816||2718||97.8||Add 97.8 ppm Ca|
|Ca (% Saturation)||65%||62.73%|
|Mg (ppm)||312||401.5||-89.6||Should level out|
|Mg (% Saturation)||15%||15.44%|
|K (ppm)||338||473||-135.1||Should level out|
|K (% Saturation)||4%||5.60%|
|Na (ppm)||74.73||31.5||43.23||Add 43.23 ppm Na|
|Na (% Saturation)||2%||0.64%|
|Other bases (% Saturdation)||5.10%|
|H+ (% Saturation)||10%||10.50%|
|B (ppm)||2.82||0.77||2.05||Add 2.18 ppm B|
|Fe (ppm)||140.56||290||-149.44||Should level out|
|Mn (ppm)||50||28||22||Add 22 ppm Mn|
|Cu (ppm)||16.89||4.98||11.91||Add 11.91 ppm Cu|
|Zn (ppm)||33.79||22.65||11.14||Add 11.14 ppm Zn|
As you can see, our garden was quite deficient in sulfur and phosphorous as well as somewhat deficient in calcium, sodium, boron, manganese, copper, and zinc. Also very importantly, our organic matter is higher than it should be, which means that the compost we were adding wasn’t being properly broken down and integrated into the soil to become humus. Clearly just adding compost is not enough without proper mineral balance. As organic matter breaks down, a lack of sulfur can result in nitrogen loss to the air or leaching, and a lack of calcium can result in loss of carbon meaning that two of the most important nutrients from compost are being lost. Some of our crop failures also could be directly tied to these results, such as onions which need a lot of sulfur and phosphorus and some of our tomato plantings which had end-rot due to calcium shortage. On the other hand, our carrots and beets did great this year. Carrots and beets need a lot of potassium and do not like too much nitrogen or phosphorus.
We also had some pest issues this year, particularly with our brassicas. The theory goes that when plants have access to all the minerals they need, they will be much healthier and stronger and will therefore attract fewer pests and diseases and stand up better to any challenging growing conditions. Take this one step further, and you see that people will be much healthier if we are eating produce, grains, and animal products that during growth were provided with the minerals needed to be healthy. I will be very curious to see what difference our efforts have made for the health of our gardens and quality of our produce this coming season.
Stay tuned for Part 2 where I will go into detail on the mineral amendments we added to the garden, where we bought them, and how we went about adding them.