2000 was the third in a four-year study looking at varying levels of soil disturbance of four single shoot openers (angle disc, knife, spoon and sweep) on four different crops and the effect of the level of soil disturbance on weed densities. The site is located at Aneroid, one hour southeast of Swift Current, in the Dry Brown Soil Zone. One of the unique features of this study is that each opener seeds a particular plot throughout the study. Although the crops on that plot rotate in a cereal/broadleaf rotation, a plot seeded with a particular opener is seeded with that opener through the four years of the study. In this way, we are able to observe changes in weed densities over this study period. In addition, there are glyphosate pre-seeding burnoff treatments and non-burnoff treatments to see if there are any advantages to this practice, especially on high disturbance openers.
There wasn't a lot of difference in crop establishment between the four openers with chickpeas (Figure 1). However, with the peas, barley and durum, the sweep generally resulted in the lowest crop establishment.
Figure 1. Crop establishments 2000, Aneroid.
The trend continued in 2000 as it has over the previous two years in that the angle disc resulted in the lowest weed density compared to the other three openers (Figure 2).
Figure 2. Weed density of first weed count, Aneroid 2000.
The knife appears to be starting to have lower weed densities compared to the first two years when compared to the densities with the spoon and sweep. Another trend developing is that the sweep and spoon tend to have the highest weed populations in most of the crops in this study. Another trend in 2000 was the higher the disturbance the opener is, the higher the broadleaf weed population (data not shown) in barley and durum. An interesting development occurred on the barley with all openers. There were very few broadleaf weeds, particularly kochia and wild buckwheat, in the barley plots. This was a bit of a surprise except when I looked back at the records and realized that the barley was seeded on field pea stubble. In 1999, the field pea plots had an in-crop application of Odyssey. It was quite apparent that there was some residual effect of that application on broadleaf weeds in 2000.
With respect to yield, for all crops except durum, the yield decreased with increased soil disturbance caused by the opener (Figure 3). There seemed to be much more variability with the durum yield between the openers.
Figure 3. Yields of all crops using the four openers, Aneroid, 2000.
In summary, it appears that the angle disc results in significantly lower weed densities and is generally at the top end of the yield compared to the other three openers. However, the knife is now starting a trend of lower weed densities as compared to the previous two years. It appears that it takes the knife a few years before weed densities are lowered and yields are close to those of the angle disc. I suspect that this trend will continue in 2001. The sweep is showing a trend of higher weed densities and lower yields. The advantages of the high disturbance opener tend to be in the very short term and are not sustained over several years. I would like to emphasize again that the angle disc is like any other opener and is not appropriate for all regions of the province or soil zones. It does appear to present some major advantages in the Brown and Dry Brown Soil Zones.