Research was conducted at Reading University over three growing seasons into alternatives to herbicides m spnng cereals by identifying traits that enhance crop competitive ability and exammmg the role of seed quality in Integrated Weed Management (IWM~. Nine spring wheat genotypes, spring Barley, spring Triticale and a mixture of spring wheat genotypes Paragon and Belvoir were monitored for their competitive ability in three weed treatments, i.e. weed free and with model weeds Sinapis alba L. or Avena sativa L. The ranking of competitive ability (CA) was estimated from both crop tolerances to weed pressure (i.e. a low crop grain yield loss - CYL) and weed suppression. Genotypic differences in CA were repeatable, with CYL of 28%, 39% and 28-75% for barley, triticale and wheat in 2003, respectively. Barley also suppressed weed biomass by 59% more than wheat. Among wheats, Axona consistently maintained higher yields (10% CYL in 2002 and 46% in 2003). Paragon suppressed weeds by 63% in 2002 and 50% in 2003 whereas cv. Status was a poor competitor. The wheat mixture reduced CYL but had no significant effect on weed suppression. An important observation for variety trials was that the ranking for grain yields in weed free plots was inconsistent with those with weeds. Competitive genotypes tended to be taller and have rapid early growth at GS 15 giving early ground cover, a higher absolute growth rate at GSI5, a shorter mean time to emergence and higher early leave area. On seed quality and its interactions with agronomic practices such as seeding rate and sowing date, doubling seed rate improved crop competitiveness if the crop was sown at the same time as weeds rather than a week later. When a vigorous seed lot was used, higher number of seedlings, ground cover, harvest index and number of fertile tillers per m2 and lower mean time to emergence contributed to its higher crop grain yield. High vigour seeds suppressed total weed biomass up to 89,-43 and 63% in three experiments, the suppression varying between individual weed species. For example, when natural weed infestations were present, high vigour seeds suppressed Convolvulus arvensis L. by 52.5% and Solanum nigrum L. by 95.5%. One particular feature of this thesis was an attempt to understand why high vigour seeds are more competitive. The results indicated that more than 75% of the variations in grain yield and 81 % of the variation in weed dry mutter suppression can be accounted for due to achieving more rapid emergence than the weeds.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553091 |
| Date | January 2007 |
| Creators | Al-Allagi, Musa |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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