10 Years Later

The Long-Term Effect of a Single Lime Application

Photo by Carol Windels

A University of Minnesota study has further documented the long-term impact of a single application of spent lime. In January, Ashok Chanda and Jason Brantner* of the University of Minnesota’s Northwest Research and Outreach Center at Crookston reported on what they found 10 years after a single application of spent lime on a field near Breckenridge, Minn. Specifically, they measured effects on (1) soil pH, (2) Aphanomyces root rot and (3) sugarbeet yield and quality a decade after treatment.

In Spring 2004, as part of research on spent lime’s contribution toward managing Aphanomyces in sugarbeets, now-retired U of M plant pathologist Carol Windels and former NDSU plant pathologist Carl Bradley (currently at the University of Illinois) established a trial in that Wilkin County field north of Breckenridge. The field has very high levels of Aphanomyces, with a soil index value of 98 (100 being the highest possible level). The field’s pH registered at 6.3. Spent lime treatments — each replicated four times — went on at rates of zero, five, 10, 15 and 20 wet-weight tons per acre (zero, 2.7, 5.3, 8.0 and 10.6 dry-weight basis). Spring wheat was planted that year to allow the lime treatments to stabilize. Since then, sugarbeets have been grown in one experiment each year (2005 through 2014) in rotation with wheat, corn and soybean.


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The Experiment 2 area, where sugarbeets were planted in 2014, last had beets on it in 2010; and before that, in 2006. Two Roundup Ready® varieties were planted: one being susceptible to Aphanomyces, the other rated as partially resistant. The susceptible variety was not treated with Tachigaren, whereas the partially resistant one was treated with 45 g of Tachigaren per unit. Standard fertility and production practices were followed throughout the season in order to achieve maximum sucrose yield and quality. Stand counts were made at five and seven weeks after planting, and soil samples were collected in June to test soil pH and Aphanomyces soil index values.

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* Ashok Chanda and Jason Brantner are asst. professor/plant pathology and research fellow, respectively, with the University of Minnesota’s Northwest Research and Outreach Center, Crookston.

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So what did the 2014 evaluations discover?

• First, there were significant interactions between rate of lime and sugarbeet variety for stand at five and seven weeks after planting, Chanda and Brantner report. For the susceptible variety without Tachigaren, stand counts at seven weeks after planting were 125, 175, 201, 219 and 221 plants per 100 feet of row for zero, five, 10, 15 and 20 tons of lime, respectively. For the resistant variety treated with Tachigaren, “stands were protected, so that they were not significantly lower without lime,” they note.
  

• Table 1 shows how the resistant (“Res.”) and susceptible (“Susc.”) varieties responded to the various lime rates in terms of Aphanomyces root rot rating, yield and recoverable sucrose per acre (RSA). “The susceptible variety showed a very strong linear response to rate of lime for all harvest parameters,” the UM researchers point out, while the resistant variety “also had a significant — but not as steep — response to lime rate for number of harvested roots, Aphanomyces root rot rating, yield and [RSA].” When it came to percent sugar, both varieties responded similarly to lime rate.
  

• As of June 2014, 10 years after the lime application was made, soil pH in the tested site was 6.5, 7.2, 7.5, 7.9 and 8.0 in plots treated with zero, five, 10, 15 and 20 tons of lime per acre, respectively. “These pH values followed a similar trend as those measured three months after [the] lime was applied in 2004,” Chanda and Brantner report.
  

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There was a significant reduction in Aphanomyces root rot and increased beet yield as a result of that single application a decade ago.

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• Aphanomyces soil index values (SIVs) were high in all plots as of 2014, but there was a significant response to the rate of lime applied in 2004. The SIVs averaged 100, 100, 100, 93 and 94 in plots with zero, five, 10, 15 and 20 tons/acre, respectively. Extractable calcium increased significantly as well with increasing rates of lime.
  

Conditions at Breckenridge in 2014 were conducive for early season damping- off and for root rot throughout the season, the U of M investigators note. Planting was late (May 22), and June rainfall at the nearby Wahpeton, N.D., station of NDAWN was 5.80 inches — 2.52 inches above normal. This resulted in warm, moist, favorable soils for infection by Aphanomyces. “During this period, the resistant variety was protected by Tachigaren and had good stands, regardless of lime rate,” they note. “The susceptible variety without Tachigaren, however, lost seedlings to damping off in non-limed control plots and in those plots receiving a 5.0-ton lime application.” Lower-than-normal rainfall in July allowed plants that had survived to recover; however, high rainfall in August resulted in new infections, impacting harvest parameters for both varieties.

Disease pressure — both early and late in the season — resulted in significant responses to rate of lime for both varieties. The partially resistant variety with Tachigaren was better able to withstand early disease pressure, and had less yield loss without lime; that meant a less significant response to lime rate. The susceptible variety without Tachigaren, by contrast, performed very poorly without lime — but had excellent yields and recoverable sucrose as lime rate increased.

The primary conclusions from the 2014 Breckenridge evaluation, Chanda and Brantner state, were as follows:

First, 10 years after the application of spent lime, there was a significant reduction in Aphanomyces root rot and increased beet yields, as a result of that single application a decade ago.

Second, soil pH levels initially increased with application of spent lime and have remained relatively stable for 10 years.

Third, though they have fluctuated over the 10-year period since the lime was applied, soil index values (SIVs) in limed plots measured high in 2014.


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