All I can say about the 2002 crop year is "Thank goodness it's over!" Actually I had used several other adjectives to describe this past year, but the editor thought this expression of opinion was the only printable one. At least most areas of the province have a good soil moisture reserve for next year, which was not the case at seeding time in 2002. So, as an optimist, one looks towards next year as the one that will bring a bumper crop. In that vein, it is not too early to be planning for the new crop year.
Although we certainly hope that we don't experience a repeat of 2002, there were things we can learn from our experiences. The spring of 2002 presented a situation of very dry soil and cold temperatures. As a result, few weeds germinated by seeding time so few farmers were willing to apply a pre-seeding burnoff. Most were counting on being able to apply the burnoff after seeding but before the crop came up. However, in many cases, the crop started to emerge before many producers were able to apply the burnoff. The questions started to pour in on whether farmers could still apply a Roundup burnoff when some of the crop was already emerged. As it happens, I had a demo project located at the Swift Current Agri-ARM applied research farm site that dealt with this issue.
This demo showed the effect of applying a Roundup burnoff at different times of application to durum wheat, field peas and chickpeas. Each crop had separate plots showing the effect of the Roundup that was applied at pre-emergent, ground crack, 1 day, 2 days and 3 days after ground crack. Ground crack is a term used to describe when the crop is just poking through the soil surface. This demo provided good evidence of what are the consequences of applying glyphosate once the crop emerges.
The chickpeas showed the least effect, but this may have been a result of the very cold environment at time of the treatments and uptake of glyphosate may well have been limited. In both the field peas and the chickpeas, the glyphosate treatment did not kill the crop even 3 days after ground crack. However, don't get too excited over this news, because what it did do was severely stunt the crop and also practically stopped any nodulation. Any nodules that were present on the roots were not fixing nitrogen. The roots also were stunted in development and were curled up indicating herbicide damage.
The peas that had Roundup applied 3 days after ground crack really didn't grow any taller than seven inches. Looking at the peas, the plots looked a bit like steps with the pre-emergent and ground crack plots being about the same height with the crop being shorter for each day after emergence the glyphosate was applied. Now I know you are probably saying that you wouldn't spray a burnoff 3 days after the crop emerged. However, even though there was virtually no difference in plant height between the pre-emergent and ground crack treatments, there was still a difference in crop development between these two timings. When the pre-emergent peas were in flat pod stage, the ground crack peas were still in flowering stage. That isn't much of a difference, but it does show how some effects are not so evident. The peas that had Roundup applied 1 day after ground crack showed stunting effects and those plants that had come in contact with glyphosate were not flowering or only had one or two flowers in total.
In the durum wheat, it became very quickly evident that wheat has VERY little tolerance to Roundup. The 1 day after ground crack treatment showed significant reductions in plant populations with less than half the plant populations of the pre-emergent burnoff treatment. Essentially, if the wheat was exposed to Roundup at all, it was killed. Where the Roundup was applied on the third day after ground crack, it essentially became chem fallow. There was virtually no wheat left.
The lesson we can take from this is applying a burnoff with any glyphosate once the crop is up is a tremendous risk. Sure the weed control was better by the second and third day after ground crack of the crop, but correspondingly, the higher the damage to the crop. Waiting until ground crack to start spraying a burnoff with Roundup can also be quite risky. The risk being that the growth of the crop seedlings can progress very quickly, especially under good growing conditions. A crop that is just at ground crack stage in the morning can have a high percentage of the crop well out of the soil by the afternoon. The decision on continuing to spray a burnoff rests with the producer on how much risk he is willing to take. However, if there is more than 5% of the crop up at the time you want to spray a burnoff with a glyphosate like Roundup, my feeling is that it is too risky to continue.