Soil Chemistry Guidelines
This week saw the delivery of NOFA’s newspaper Natural Farmer, which is always chock full of amazingly useful information. The paper is quarterly and usually features a pull out section on a particular topic, this one being the topic of Nutrient Density. There’s a fabulous long interview with farmer and consultant Mark Fulford of Teltane Farms in Maine.
In talking about soil nutrients, Fulford offered a very concise useful nugget about soil chemistry, which I’ve tried to capture in the table below.
UPDATE: 20100115: Here’s a better version of the table with original following:
| Element | Aspect | Function | Form | Notes |
| Nitrogen (N) | Vegetative | Growth | Nitrate - N03 | |
| Nitrogen | Reproductive | Seed, fruit, root | Ammonia- NH3 | some plants switch from growth to reproductive, esp. tomatoes and potatoes |
| Carbon (C) | Energy storage, binding, nutrient availability, soil “digestion” | e.g. Calcium carbonate | ||
| Phosphorus (P) | Reproductive | Seed, fruit, root | Phosphate- many forms | called a “salt”; rock phosphate, bird and bat guano as a source |
| Sulphur (S) | Reproductive | Seed, fruit, root | Sulfate, many forms, x-SO4 | also called a “salt” |
| Manganese (Mn) | Reproductive | Seed embryo development and finishing | only need very small amounts | |
| Calcium (Ca) | Vegetative | Cell wall structure, critical for growth | Calcium carbonate- CaCO3 | Limestone, Dolomite, Gypsum |
| Potasium (K) | Vegetative | Growth | Potash, Green sand; bracken ferns recycle K | |
| Magnesium (Mg) | Vegetative | Key to chlorophyll and photosynthesis | ||
| Silicon (Si) | Vegetative | Structural; like the rebar in cell wall growth | needs organic matter to be made available |
Fulford talks about a lot of things in this lengthy article which I highly recommend. One way to assess soil chemistry is through soil testing of course, but another way is to analyze the weeds growing on a property. For example, dandelions and goldenrod indicate dry conditions, whereas buttercups indicate wet or anaerobic soils. Broadleaf weeds indicate high potassium, low phosphorus. Annual grasses indicate lack of calcium.
Fulford mentions a couple of good books on weeds:
Weeds: Why They Grow, by J. McCaman
Weeds: Control Without Poisons, by Charles Walters