The Grassweed Rotational Trial at Dow AgroSciences’ R&D facility at Wellesbourne is now in its fifth year. Research focuses on the interactions between cropping (winter wheat and winter oilseed rape), cultivation type (ploughing or shallow cultivations) and herbicide programmes (e.g. Unite, Kerb Flo 500, ASTROKerb) on the control of blackgrass, ryegrass, brome and wild oats. For harvest 2015 spring barley was also included in the rotation, to reflect practical requirements of the ‘3 Crop Rule’ and the effects this might have on grassweed control.
Key discoveries to date include:
- Cultivation has a big effect on the population of grassweeds.
- More grassweeds are found where shallow cultivations predominate, compared with where a plough is used regularly.
- Plots dominated by a shallow cultivation approach, with occasional ploughing, are beginning to show an increase in wild oat populations.
- In the continuously shallow-tilled area there is an indication that sterile brome is becoming the dominant grassweed.
- The areas that have been ploughed during the trial have given a visible reduction in all grassweeds, especially where ploughing has taken place every autumn.
- The largest reduction in grassweed numbers was seen when several years of ploughing was followed by shallow cultivations then back to the plough again.
- In the areas ploughed every autumn, the numbers of broadleaved weeds are much higher than when a combination of the two seedbed preparation methods, or continuous shallow cultivations, is used.
- The trial is showing the benefits of an integrated approach to crop production and the importance of varying the methods of crop establishment, with shallow cultivations and ploughing. This is only true if the plough is set up correctly, as poor ploughing can lead to little benefit.
- The herbicide programmes used in winter wheat and winter oilseed rape achieved excellent levels of grassweed control.
- The spring barley established after shallow cultivations had a particularly high population of wild oats.
- Ploughing before drilling consistently shows better crop establishment.
- Improved establishment is not necessarily translated into higher yields.
- The highest yields for winter oilseed rape were from an area ploughed in 2013 but established after shallow cultivations in autumn 2014.
- The first wheat out-yielded the second wheat, which in turn performed better than the continuous wheat.
- Ploughing or a combination over the years of ploughing and shallow cultivations gave a yield benefit over continuous shallow cultivations.
- Spring barley, introduced in spring 2015, gave higher yields when it was established behind the plough rather than shallow cultivations.
|Autumn 2013||May 2014|
|Both images show the difference in weed population and crop density of continuous shallow cultivation on the left of the field, and introduction of the plough in year 3 on the right of the field.|