A field trial programme was started in 1987 covering the main arable areas of the UK, comparing the Long Ashton (LARS) Crop Equivalent system for determining the need for herbicide in cereals against insurance spraying. In Scotland, 4 trials were established in East and West Lothian with both the LARS system and insurance spraying at full and half the recommended rate of chemical against an untreated control. The trials were to last 4 years with each treatment in the same location throughout the period to allow changes in the weed seed bank to be studied. Cropping years 1988-90 included 4 crops of spring barley, 5 of winter wheat and 3 of winter barley. At all sites there were significant effects of treatments on weed seed numbers in the trial with 3 crops of winter barley at Smiths where <I>Stellaria</I> <I>media</I> seed in the soil increased from 156/m<SUP>2</SUP> of soil in 1988 to 11789/m<SUP>2</SUP> in 1990. There was a large response to herbicide use for all the winter barley crops. but no clear response for spring barley and winter wheat. The half rate and threshold treatments tended to give the best margins for most crops. In some years, weeds were found to have an economic effect on crop harvesting above that predicted by the LARS threshold system. Cost of assessment was thought to be a major drawback of the LARS system and an alternative of reducing herbicide dose to suit field conditions was tested from autumn 1988. This proved successful in finding some of the major factors which affect the optimum dose of herbicide in a given field. Factors included weed species, active ingredient, weed size and weed number.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:663724 |
| Date | January 1995 |
| Creators | Whiting, Andrew John |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14661 |
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