Chapter 6

Cover Crops for Organic Farms

Life Cycle of Cover Crops

Cover crops are usually classified by temporal occurrence, divided into annuals that last up to one year, perennials that continue to grow indefinitely or that regrow each year, and biennials that take two entire seasons to reach the reproductive stage. The intended use dictates which group is most suitable for a given situation. Table 7.1 describes several of the more commonly used cover crops. Some of the characteristics of each species listed include life cycle, winter hardiness, nitrogen fixation or nutrient scavenging potential, and several advantages and disadvantages.

Annual Cover Crops

By definition, annual cover crops complete their lifecycle in a year. Annual cover crops can be grains/grasses or legumes (those that produce nitrogen), and are either summer or winter cover crops. Winter cover crops (e.g., hairy vetch) are adapted to shorter, cooler days, while summer cover crops (e.g., such as cowpea) are better for hot, long-hour days. One reason for growing annual cover crops is to provide seasonal soil conservation in the winter months following harvest of the cash crop.

Perennial Cover Crops

Perennial cover crops can be short-lived (only a few years) or they can be long-lived for many growing seasons. In warmer and milder climates, perennial cover crops can grow continuously. In seasonal climates, their growth is limited to the growing season. Many perennials will not flower until after a few years of growth. Perennial cover crops are mainly herbaceous. Perennial cover crops can reproduce from various types of offshoots (e.g., bulbs, tubers, rhizomes) from a parent plant, or they can reproduce from seed just like annuals, or in both ways, once again depending on the species.

Biennial Cover Crops

Biennials are plants that take two entire seasons to reach the reproductive stage. The first year is a time for accumulating food reserves in storage organs. The second season produces reproductive flowers and seeds.

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