From our kitchen window we can see a freshly disced portion of our front fields with a faint green stubble just becoming apparent. In a few months this stubble will become a seven-foot tall sea of brilliant green grass with waves blown across it by the afternoon wind.
Like most organic farmers we rely on cover crops (crops which are chopped and incorporated back into the soil) for a large share of our soil fertility. In our area cover crops are primarily grown in the off-season and incorporated before planting in the spring. These cool season cover crops often consist of legumes like vetch, peas, or bell beans combined with a grain, typically barley or oats. These leguminous plants work together in a symbiotic relationship with a soilborne bacteria to fix nitrogen from the atmosphere. When these cover crops are incorporated this nitrogen becomes available to our vegetable and flower crops at up to 275 pounds per acre.
Because, however, we tie up a lot of our land with overwintering crops (all of the flowers you’ve received so far, and the majority of the vegetables you’ve received from Andy were from plantings made last year) we aren’t always able to take advantage of the off-season to grow cover crops.
Hence the use of warm season cover crops, which are planted in the spring and summer and incorporated in the fall. In general these are a different group of plants that like warmer, drier conditions. The larger farms in our area rarely use them because they are reluctant to tie up land during the prime growing months. I, however, feel that the improvement in soil quality and the quality of the crops we follow them with make summer cover crops entirely justified.
Although we’ve tried cowpeas and buckwheat, the warm season cover crop we really like best here at High Ground is sudan grass. Closely related to sorghum, this grain produces huge amounts of Organic Matter, growing to seven feet and taller on good soils. And it doesn’t require much water—after getting established we only irrigated last year’s crop 2 or 3 times. Sudan grass also does a great job of choking out weeds. Although many weed seeds germinate along with the sudan at first, it grows so rapidly that it completely shades out the weeds, greatly reducing or eliminating the amount of seeds they produce.
In addition to providing organic matter and reducing weed pressure, a summer cover crop rotation also allows earthworm populations to rebound and improves the structure of the soil by giving it a break from tillage operations.
My ultimate goal in managing our farm is to not let any piece of ground sit truly idle—with nothing growing on it. As a general guideline I try not to plant more than three successive crops on any piece of ground without a cover crop rotation, either cool or warm season, being worked in. Besides all of the other benefits, a sea of beautiful green grass is a lot nicer to look at than bare ground when you’re washing dishes.
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