Compost is queen in organic gardening, but it’s not the only soil- improvement tool in the kit. Healthy soil includes plenty of minerals and micronutrients, as well as organic matter. That’s where Greensand comes in.
Greensand is a rich source of marine potash, silica, iron oxide, magnesia, lime, phosphoric acid, and 22 other trace minerals because it’s mined from the deposits of ancient shallow seabeds. Technically known as glauconite, this blue-green mineral is found throughout the world. It was an important soil conditioner and source of potassium fertilizer for more than 100 years prior to the advent of commercially prepared, variable-nutrient formulas. Organic farmers and gardeners have never given up on greensand, however.
Potash, the potassium or K in the N-P-K fertilizer ratio, is crucial for overall plant health. It increases disease- and pest-resistance, improves winter hardiness, and helps plants use water more efficiently. Plants use a lot of potassium, and it’s second only to nitrogen as a major nutrient found in plant tissues. Potassium deficiency symptoms include yellow to brown leaf margins and stunted growth.
Potassium moves readily in the soil and plants use quite a bit of it, so it needs replenishing regularly. Greensand releases its potassium gradually as soil organisms do their magic, ensuring a continuous supply of this essential nutrient. It’s an especially valuable additive in nutrient-poor sandy soil and in high-rainfall climates. Greensand also helps lighten heavy clay soils.
For more in-depth information about the role of potassium in plants, read Potassium and Its Role in Crop Growth.
For an entertaining description of how one Texas gardener used Greensand to improve his yellow lawn, visit his blog.