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:
|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: