Your choice of green manure seeds to increase soil health will depend on how long the section of land will not be farmed, what time of year it is, the available soil type, and the desired nitrogen level of the vacant land. Some green manure crops grow quickly and others take longer to grow to maturity, so this choice is based on how soon the land will be used for yield crops. There are varieties of green manure that typically do not survive overwintering. One popular type of green manure are the legumes, such as peas, chickpeas, clover, and beans, which will increase nitrogen in the composition of the soil. Soil drainage capability should also be taken into consideration when choosing a type of green manure.
Green manure seeds refer to the seeds of crops that are grown solely to protect and nourish the soil when it would otherwise lie fallow, for periods of time ranging from several weeks to longer than one year. These crops help avoid soil erosion and excessive drying as well as invasion by weeds. They also improve soil composition by increasing the nitrogen levels, numbers of helpful microorganisms, and penetration of water and air. Further, the use of green manure seeds in otherwise unused crop land provides habitats for beneficial wildlife, such as bees.
The type of green manure seeds you choose can be based primarily on your intention for the land. If you want to keep weeds from gaining a foothold, an appropriate choice might be cowpea, buckwheat, or lucerne. Rapeseed is a green manure crop known to aid in suppressing certain kinds of plant diseases, such as root rot. It is possible to use a mixture of some types of green manure seeds, such as clover, rye, and vetch.
A traditional method for using green manure seeds is to allow the green manure crop to continue growing until they are close to flowering. Then, the crop is hoed down. The cut-down plants are either tilled into the soil or left to decompose as a protective layer on top of the soil. In this way, the green manure crop nourishes the soil in preparation for a different crop that will be grown for money or personal food use. Typically, it is best to wait up to several weeks before sowing the new crop for optimum soil retention of nutrients from the green manure crop.