Individual study: Crop-weed interference as influenced by a leguminous or synthetic fertilizer nitrogen source: I. doublecropping experiments with crimson clover, sweet corn, and lambsquarters
Dyck E., Liebman M. & Erich M.S. (1995) Crop-weed interference as influenced by a leguminous or synthetic fertilizer nitrogen source: I. doublecropping experiments with crimson clover, sweet corn, and lambsquarters. Agriculture, Ecosystems & Environment, 56, 93-108
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Incorporate plant remains into the soil that produce weed-controlling chemicals
Two randomised, replicated, controlled trials in 1989-1990 in Maine, USA (Dyck et al. 1995) found that incorporating crimson clover Trifolium incarnatum residues into soil reduced emergence of lambsquarters Chenopodium album and other weeds compared to plots treated with nitrogen fertilizer. Maize Zea mays growth was initially 31% lower in plots with clover residue but returned to fertilized plot levels over the growing season. Lambsquarters growth was significantly reduced in plots of crimson clover compared to fertilized plots, with reductions of 64-81% two weeks after emergence and 37-42% lower at the final sampling date. Less maize drymatter was lost to weeds in the crimson clover treatment than the fertilized treatment (1989: 14 vs. 36%; 1990: 0-2 vs. 19-21%). Maize was grown in 3 x 9.1 m plots, each split to contain maize only or maize with lambsquarters. Other weeds were removed. There were six treatments: crimson clover residue, no fertilizer or residue and four levels of ammonium nitrate fertilizer (45, 90, 135, 180 kg N/ha). Crimson clover was sown at 84 kg/ha in May, then mown and incorporated 10-15 cm-deep on flowering. Maize was sown within 2 days of clover incorporation. A second trial in 1989 tested the effect of crimson clover residue applied to plots of lambsquarters.