The four-year Opener/Rotation Study located soutwestern Saskatchewan is now completed. The site, located at Aneroid, SK, an hour southeast of Swift Current, produced some expected and unexpected results. The study evaluated four single shoot openers (angle disc, knife, spoon and sweep) with different levels of soil disturbance. Four crops (peas, desi chickpeas, barley and durum) were used in the study in a cereal/pulse rotation. One of the unique features of this study was that each opener seeds a particular plot throughout the study. In this way, we are able to observe changes in weed densities over the length of the study as affected by each opener.
Over the four years, the angle disc consistently had the highest crop establishments, with the knife not all that far behind on some crops. Although all openers, even the sweep, benefited from a glyphosate burnoff, it was obvious that the lower the level of opener disturbance, the greater the reduction in crop establishment that occurred when there was no glyphosate burnoff.
As expected,
the angle disc consistently produced the lowest weed densities
over the four-year study (Figure 1). Compared to the other
openers, the angle disc resulted in a significant reduction in
weed densities the first year of the study. However, what wasn't
expected was the knife taking
Figure 1: Average 1998-2001 weed densities of the four openers on all crops, burnoff treatment.
so long before realizing lower weed densities and improved yields. It appears that it takes a period of time, in this case at least three years before the weed seed bank in the soil is reduced enough to result in a reduction in weed densities. The four-year averages in Figure 1 do not indicate this trend. However, the average of the 2000 and 2001 weed counts does illustrate this trend of reduced weed densities with the knife (Figure 2). In addition, Figure 2 also shows the trend of openers with increasing levels of soil disturbance having a corresponding increase in weed densities. A longer study would likely reflect this in the long-term weed density averages. Another noticeable trend was that over time, on the no glyphosate burnoff plots seeded with an angle disc, and to a lesser degree the knife, foxtail barley and some Canada thistle became established. However, the burnoff treatments using these openers essentially kept the incursion of these perennial weeds from developing.
Figure 2:
Average weed densities of the four openers on all crops from
2000-2001, burnoff treatment.
Crop rotation also had an effect on weed densities. Due to practically no options for broadleaf weed control in chickpeas (especially kochia and wild buckwheat) and the crop's poor competitive ability with weeds, it is no surprise that weed densities in chickpeas are high. This also affects the cereal crop following chickpeas. Another trend developed with peas. As noticed in previous years, there was a trend of lower weed densities in the cereal crop following peas. When the grassy vs. broadleaf weed densities were compared, it was evident that broadleaf weed densities were significantly lower in the cereal crop on pea stubble as compared to the other crops. This is very likely the result of the residual carryover from the herbicide Odyssey applied to the filed peas.
Yields have
followed a similar trend as with weed densities. The lower the
disturbance created Figure 3: Average yields 1998-2001 with the
four openers on all crops, burnoff treatment.
by the opener, the higher the potential the yield (Figure 3). As with the weed densities, the lower the soil disturbance opener used, the more important it is to use a glyphosate burnoff. Also evident is that any advantage of sweeps is relatively short-term. The longer one uses sweeps, the higher the weed problems become and the lower the yields compared to lower disturbance openers. In addition, under dry soil conditions, the higher disturbance openers have significantly higher problems with the seedbed drying out. Under wet conditions, crop establishment is not generally affected by the level of soil disturbance from the opener.
As with the weed density figures, 2000 and 2001 appeared to be the ongoing trend that reflected the potential of each opener over time. The yields from the knife were becoming closer to those of the angle disc and it was becoming more evident as time went on, that the higher the
Figure 4: Average yields from 2000-2001 with the four openers on all crops, burnoff treatment.
disturbance of the opener, the more weed pressure occurred and subsequently, the less yield potential could be expected (Figure 4).
While the angle disc generally produced the best results overall, not all producers are prepared to opt for a low disturbance disc opener for direct seeding. What is important to note is that there are pro's and con's to each opener choice. While many producers opt for a sweep when switching to direct seeding, it is important to recognize that any potential benefits from this opener are relatively short-lived. In addition, adequate packing becomes more difficult and dry-down of the seedbed in dry years is severe. Not surprisingly, under wet conditions crop establishment is not affected a great deal by the opener. Under dry conditions, the level of soil disturbance significantly affects crop establishment. The lower disturbance hoe-type openers like the knife do provide higher yield potentials over time. However it will take a certain amount of time to realize that potential with knives. Low disturbance disc openers, such as was used in this study, have a great potential in the Dry Brown, Brown and likely the drier parts of the Dark Brow Soil Zones. However, the producer must realize a little different management and understanding of the strengths and weaknesses of disc openers before opting for this choice. Anecdotal evidence (that I witnessed first-hand) indicated that under severe dry spring soil conditions, as was experienced in 2001, the angle disc had trouble maintaining the desired depth in stony ground for deeper seeded crops like chickpeas or peas.
Crop rotations also have shown to play a significant role in the level weed problems that can be expected. The choice of crops and the herbicides available for the in-crop weed control also play a major role in levels of weed problems. In addition, all crops and all openers did benefit from a pre-emergent burnoff with a glyphosate. However, the lower the level of disturbance of the opener, the more important this burnoff becomes. No matter what opener a producer chooses there are agronomic influences on the potential success of the opener. Producers also need to be aware of the long-term and short-term effects of a particular opener. However, this study does show significant advantages of low disturbance openers over high disturbance openers.
Wheatland
Conservation Area and SSCA conducted the work on this project.
Funding for the last three years was from the Agri-Food
Innovation Fund (AFIF) and the first year by a combination of
funding SAF, Southwest Regional Council of ADD Boards, SSCA, and
District #4 ADD Board.