Green Manures

Green manures improve soil in a variety of ways. Green manures add significant amount of organic matter into the soil. Like animal manures, the decomposing of green manures works to enhance biological activity in the soil. Green manures can also diminish the frequency of common weeds, and when used in a crop rotation, they can help to reduce disease and pests. When turned under, the rotting vegetation supports beneficial bacterial populations.

Alfalfa roots regularly grow to depths of five feet or more, because those deep reaching roots leave behind minute channels deep into the soil. When these deep roots decay, they provide organic matter that promotes long-term soil building.

However, to be truly beneficial to the marijuana grower, green manures needed to be used for outdoor planting. When opting to not use an outdoor marijuana grow spot plant sprouts to rejuvenate the soil natural. Use a cover crop. Then return to the spot the following year to reap a bountiful reward of rich soil requiring no nutrients.

With careful stewardship, a legume cover crop can enrich the soil with enough nitrogen to supply most of the following years crop nitrogen needs. Commonly used legumes for cover crops include: alfalfa; fava, mung and soy beans; a whole variety of clovers; cowpeas and field peas; common or hairy vetch; the lupines; and finally our favorite name among the legume cover crops - Birdsfoot trefoil.

The use of green manures and cover crops is relatively simple, the primary necessity being the time to grow the plants. Some pre planning is always helpful to make sure the correct crop is selected to best meet the grower’s needs. So, for example, if enriching soil nitrogen levels is a goal, then it’s best to choose a cover crop from the legume family due to their ability to fix nitrogen.

Some green manure plantings tolerate poor soil quality better than others, so some cover crops may be chosen because they tolerate particularly acidic (or alkaline) conditions. If a grower needs to break up hardpan soil and improve drainage, some cover crops grow very strong and deep roots. Such conditions call for green manures like alfalfa and birdsfoot trefoil that can thrust their roots through anything but the most dreadfully compressed soils.

As stated earlier, deep-rooted plants can also bring up essential nutrients from the subsoil. And, some do even more; they actually accumulate nutrients, concentrating them. Growing these green manures can produce a measurable (although not huge) increase in soil nutrients. Some legumes, especially red clover, can help to increase phosphorus levels. Buckwheat also increases phosphorus, as well as helping to supplement calcium. Vetches are also accumulator plants, working to increase levels of both calcium and sulfur.

Garden centers or hydro shops are usually better sources for the more exotic ingredients like worm castings and the various bat and bird guanos.

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