Seed persistence and weed management

Persistence of seeds in the soil has consequences for many aspects of weed management. By allowing a given generation of seeds to test the suitability of several growing seasons, a seed bank buffers annual species against a year in which little reproduction is possible (Cohen, 1966). This protects the weed against local extinction, but from the grower's point of view, it makes weeds with seed banks highly resistant to eradication. However, complete eradication is rarely necessary, and knowledge of seed longevity of a species allows some predictability regarding how long perfect control of the weed is required to reduce weed pressure by a given amount (Donald & Zimdahl, 1987). Similarly, rotation into a sod crop allows several years for mortality to reduce the seed bank (Thurston, 1966; Warnes & Andersen, 1984). The effect of rotation on seed banks is discussed further in Chapter 7.

Seed longevity of a species also has a large effect on its response to different tillage regimes, and, as explained in Chapter 4, may be an important factor contributing to the shift from broadleaf species to grasses with reduced tillage. Finally, accumulation of high densities of seeds in the soil allows dispersal in soil clinging to animals, vehicles, and tillage machinery, and this is probably an important route for dispersal of weeds between fields (see section "Dispersal of seeds and ramets" below).

Growing Soilless

Growing Soilless

This is an easy-to-follow, step-by-step guide to growing organic, healthy vegetable, herbs and house plants without soil. Clearly illustrated with black and white line drawings, the book covers every aspect of home hydroponic gardening.

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