Living cover crops

Weed seedling emergence was stimulated when living cover crop biomass was incorporated into the soil. Stimulation for morningglory ranged from 172 to 409%... 

Hairy vetch (V. villosa Roth) Cover crop Residue or living mulch Cover crop residues... 

Teasdale JR, Abdul-Baki AA (1998) Comparison of mixtures vs. monocultures of cover crops for fresh-market tomato production with and without herbicide. Hort Sci 33 1163-1166 Teasdale JR, Daughtry CST (1993) Weed suppression by live and desiccated hairy vetch. Weed Sci 41 207-212... 

Residues of hairy vetch following desiccation with a contact herbicide in Maryland reduced weed emergence during the first 4 weeks after desiccation (Teasdale, 1993 Teasdale and Daughtry, 1993). However, as hairy vetch residues decomposed, weed emergence became similar to that without a cover crop and a comparable weed biomass resulted. A living mulch of hairy vetch in the no-treatment control or a dead mulch in the mowed treatment improved weed control during the first 6 weeks of the season, but weed control deteriorated thereafter. 

Another plant with great allelopathic effect is the Barley. It is integrated with other crops to inhibit weed growth which is mediated by alkaloids released from barley plant components and/or exuded from living roots. High allelopathic effectiveness of barley has resulted in its wide adoption as a cover crop in sustainable agricultural systems for weed management. The allelopathic... 

Fig. 3.14 Mean total phenolic acid (femlic acid equivalents) content of 0-2.5 cm Cecil soil samples taken during the 1992 and 1993 growing season for reference plots (no-cover crop) and cover crop plots. In 1992 cover crops were desiccated with glyphosate in April. In 1993 cover crops were desiccated with glyphosate at two time periods (April and May) and living biomass was tilled into plots in May. The absence of standard error bars indicates that the error bars are too small to be visible. Figure based on data from Blum et al. (1997). Henry A Wallace Institute for Alternative Agriculture Inc, data used with permission of Cambridge University Press...

Burning fossil fuel releases carbon into the atmosphere—more than 6.3 billion tons in 1998 alone. Significant amounts of carbon also come from burning of live wood and deadwood. Such fires are often deliberately set to clear land for crops and pastures. In 1988 the smoke from fires set in the Amazon Basin covered 1,044,000 square miles. By far the most serious implication of this is the significant threat to Earth s ecosystems by global climate change. 

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