Zone Tillage for Beet Production in Alberta

In southern Alberta, reduced tillage in sugarbeet fields has contributed to improved control of wind erosion and, correspondingly, better plant stands and yields. As in various U.S. beet areas, Alberta growers have become increasingly interested in the use of zone (strip) tillage** for this purpose.

During the four-year period of 2004 to 2007, we evaluated a zone-tillage system with conventional tillage in order to compare early season soil temperature and overall sugarbeet production. In 2004 and 2005, soil temperatures and speed of beet emergence were evaluated in a commercial field, using a 24-row grower-developed zone tillage implement. In 2005, 2006 and 2007, small-plot experiments evaluated soil temperature, speed of emergence and sugarbeet production. These experiments utilized a six-row research zone-tillage implement.# Each plot experiment consisted of four treatments replicated six times.

Sugarbeets followed a cereal crop in all the experiments. In the commercial field, all the straw was left on the field. In the small plots, straw was baled and removed prior to conducting the experiments. The conventionally tilled plots were worked two or more times in the fall and once in the spring, with the objective of reducing the amount of surface residue to below 25%. Fertilizer rates were identical in zone- and conventionally tilled areas in all tests.

Data loggers were installed at a depth of five centimeters (2.0”) in order to assess soil temperatures at hourly intervals. The below-ground sensors were located both within rows and also between rows in the zone-tilled treatments, but only within rows in the conventional treatments. In 2006 and 2007, logger sensors also were installed within rows at 2.5 cm (1.0”) above the soil surface.

Sugarbeet plant stands were counted between emergence and the four-leaf stages in all treatments. Measurements were taken in the small plots to quantify the percent ground cover from cereal stubble. Also, plant canopy vigor in the small plots was rated between the four- and eight-leaf growth stage.

Speed of Emergence & Plant Stand

Speed of emergence and final established plant stand did not differ significantly in 20 of 25 plant counts conducted for zone- and conventional-tillage treatments over the four-year period. In four of the five cases where significant differences did occur, plant stands were higher in conventional treatments.

In the commercial field trial in 2004, the conventional- and zone-tillage operations were conducted in the spring prior to seeding, with no significant precipitation occurring until 14 days after seeding. Under those conditions, zone-tillage treatments had significantly greater emergence 21 days after seeding; however, final stand was similar to conventional tillage.

In the commercial field trial in 2005, zone tillage was conducted in the fall while conventional strips were worked in the spring. Significant precipitation was received the day after spring conventional tillage operations were performed in this test. The speed of sugarbeet emergence in the 2005 commercial field was faster with conventional tillage than with zone tillage, although final plant count was not significantly different.

In the 2006 small plot trial, the initial sugarbeet emergence count was significantly higher in conventional-tillage treatments than in zone-tillage treatments; however, counts for the remainder of the emergence period were not significantly different.

The final established stand count was significantly higher for conventional tillage than for zone tillage in one of the five trials conducted. The established stand was significantly higher for conventional tillage in the 2005 small-plot trial. However, the actual stand achieved for zone-tillage plots was still considered in the optimum range for sugarbeet production.

Results over four years indicate that in most cases it was possible to achieve emergence stands with zone tillage that were comparable to conventional-tillage stands.

Early Season Soil Temperatures

In-row soil temperature differences between zone and conventional tillage were small. In the five trials conducted, zone tillage resulted in in-row soil temps that averaged 0.4°C (0.7°F) lower than temperatures measured in conventional plot residue. In individual experiments, the in-row soil temperature was either the same or slightly lower for zone tillage than for conventional tillage.

The undisturbed area between zone-tilled strips contained a greater accumulation of cereal residue than those areas where tillage was conducted, and this resulted in somewhat lower temperatures in the inter-row area. Averaged across the five trials, soil temperature of the inter-row area was 0.7°C (1.25°F) lower than that within the zone-tilled strips, and 1.1°C (2.0°F) lower than conventional tillage soil.

Differences in the within-row above-ground temperatures for zone and conventional tillage also were measured in two of the small-plot trials. Average hourly above-ground temperatures were 0.3°C (about 0.5°F) higher for zone tillage than for conventional tillage. That slight increase was a result of a 1.4°C (2.5°F) increase in the average daily maximum temperature for zone-tillage treatments versus conventional.

In general, the temperature data suggest that zone tillage did not have a substantial impact on above- or below-ground early season temperature compared to a conventional system.

Sugarbeet Production

Extractable sugar per acre was not significantly different between zone and conventional tillage in any of the individual small-plot trials, although conventional treatments were always slightly higher. In one of three trials, extractable sugar per ton was significantly higher for conventional tillage.

Beet yield also was significantly higher for conventional tillage in one of three trials. In all of the small-plot trials, significantly greater plant vigor was observed in June for conventional-tillage treatments as compared to zone tillage. However, the vigor differences disappeared by midsummer.

In 2007 we assessed soil nitrate levels and nitrogen supply rates in an attempt to explain the above-noted vigor differences. In-row nitrate-nitrogen levels to a 60-cm (2.0-ft.) depth, as of June 20, were 24 ppm for conventional plots and 83 ppm for zone-till plots. Our initial assessments suggested that N availability was not a contributing factor to the lower vigor observed in June in the zone-till treatments. Further experiments are planned to evaluate fertilizer rate, placement and residue interactions that might be affecting sugarbeet vigor.

Ground cover measurements in the small-plot trials showed the level of residue for zone tillage to be consistent over years — and, consistently higher than levels in conventional treatments.

Summary

Results from these four study years indicate that in most cases, it was possible to achieve emergence stands with zone tillage comparable to those in conventional tillage. Also, temperature data suggest that zone tillage did not have a substantial impact on above- or below-ground in-row early season temperature, compared to a conventional system. A more-robust leaf canopy as of June was observed in conventional treatments, and these treatments also produced slightly higher extractable sugar per acre.

The zone-tillage system studied in these trials appears to be a viable option for consideration by Alberta beet producers interested in better control of wind erosion. We will be continuing our investigations through both small-plot research and larger-scale strip trials.

* Peter Regitnig and Bryan Avison are research agronomists with Lantic, Inc. (formerly Rogers Sugar), Taber, Alberta.

** The terms “zone” and “strip” tillage are interchangeable and refer to the same farming system. While U.S. producers and industry typically employ the term “strip till,” Canadians commonly refer to it as “zone till.”

# This implement was built by the Ag Tech Centre in Lethbridge, Alta., with guidance and financial support from Alberta Sugar Beet Growers, the Lantic, Inc., Research Department, and Alberta Agriculture and Food.