In the current, extreme drought we are experiencing in Placer and Nevada counties, making decisions about row crop production can be challenging. Many of us already employ water efficient irrigation techniques like drip and mulch. But drought planning on the farm needs to be a combination of dealing with current situations while also preparing for the high probability of future, and potentially more severe drought conditions. One production decision addresses both: growing a summer cover crop. By growing a drought tolerant, summer cover crop you can productively fallow land during the dry months to conserve water. A summer cover crop will provide a large addition of soil organic matter which will increase the water retention in your soil during future growing seasons. Cover crops also add nutrition to the soil and decrease weed pressure.
There are a number of great summer cover crops to try. Sudangrass (Sorghum bicolor) is a great choice for the foothills during the heat of summer. It requires an initial watering at planting but can be dry farmed once established. Take caution before grazing ruminants on sudangrass as it contains highly toxic prussic acid (hydrocyanic acid.) Sudangrass has lower concentrations of prussic acid than its relative Sorghum or Sorghum-Sudangrass hybrids but it is still present in the leaves and roots of the plant. Hogs and chickens are less susceptible to prussic acid poisoning.
Another great choice for a summer cover crop is buckwheat (Fagopyrum esculentum.) Buckwheat will also grow in very dry conditions once established. It creates wonderful forage for bees and beneficial insects, is very fast growing, and helps make phosphorous more available in your soils (http://www.sarep.ucdavis.edu/covercrop/res/1994-1996/other/mini-review). Buckwheat's broad leaves and fast growth make it an ideal “smother crop” that will effectively shade out problematic weeds.
Cowpeas (Vigna unguiculata) is a good legume choice for the dry summer. They will add a lot of nitrogen to your soils and will also help suppress summer weeds. Both buckwheat and cowpeas can be used as forage crops as well.
Grow a bed of summer cover crop or grow an entire field. Try a mix of species or just one type of plant. Whichever choice you make, summer cover crops will help you farm productively under the constraints of drought.
For more information on summer cover crops, check out these resources:
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