Chapter 16

The Use of Cover Crops to Manage Soil

Seasonal Cover Crop Niches

Some of the common seasonal cover cropping niches include: cool-, warm-, or full-season cover crops.

Cool-Season Cover Crops

Cool-season cover crops are generally planted in late summer to fall, typically following harvest of a cash crop. Cool-season species start growth when air and soil temperatures are cool and will continue to grow during the spring and fall but go dormant or quickly die off when temperatures are warm (>80°F, 27°C). They do not tolerate cold temperatures, showing a marked slow-down in growth in the fall followed by death when frost occurs. Some crops like buckwheat, radishes, and oats will be winter-killed, so they are a good option before a cash crop is planted in early spring, or when termination options are limited. Other winter cover crops will require termination in the spring via tillage, roller-crimping, or herbicides prior to the planting of the next cash crop. Maturity dates also vary with the species and cultivar.

Warm-Season Cover Crops

Warm-season cover crops grow best with warm temperatures. Warm-season species typically start growth in late spring when soil and temperatures are warm. These plants thrive during the warm summer weather. Warm-season species typically do not tolerate frost and will die out quickly as fall temperatures fall at or below freezing. Planting cover crops grow during the summer fallow may be a good option to control weeds, scavenge nutrients, and add some organic matter. Warm-season cover crops are more common with vegetables than field crop rotations. Buckwheat, sorghum-sudangrass, millets, beans, or cowpeas are summer annuals that can fill this niche.

Full-Season Cover Crops

Full-season cover crops serve as rotational crops and are an excellent way to maximize biomass production, maximize nitrogen fixation by legumes, alleviate compaction problems, feed the soil microbial community, and suppress disease. However, this often means taking the field out of cash crop production for a season. This will especially benefit fields with low fertility, farms with limited access to manures and other sources of organic amendments, or farms that can use this cover crop as a forage for livestock. Fall seeded crops, such as winter wheat, may fit well in rotation following full season cover crops; the cover crop residues may trap snow and improve overwintering.

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