Lime

This photo, taken in 2019 at Highwood, Mont., shows a mature canola crop. The limed plot is on the right.

It can’t be denied, soils across parts of Montana are starting to acidify. Application of nitrogen fertilizer above and beyond what the plant can utilize has been named as the major cause of the problem. However, adaptation of no-till farming practices has also exacerbated the issue since high pH and low pH soils are no longer being mixed.

Although identifying the issue can be difficult, since symptoms aren’t always easy to identify, the real challenge comes in trying to find a sustainable and economical solution to Montana’s acidic soil issue. Luckily, top-notch researchers like Dr. Clain Jones and Dr. Rick Engel of Montana State University, with support from the Central Montana Ag Research Center (CARC), are not only aware of the problem, but they are working hard to find solutions for growers.

Simon Fordyce, research associate at CARC, spent the 2018 and 2019 growing seasons looking at plots of limed and un-limed soils, trying to determine if lime response could in fact be cultivar dependent. Although in its beginning stages, Fordyce’s research is laying some impressive groundwork that is shedding light on several questions.  

Fordyce looked at two locations for both years of the trial. Field pea and canola were grown on conventionally farmed plots near Highwood where the soil pH was low, around 4.5. Spring wheat and barley were grown on no-till plots near Geraldine in soils with a pH closer to 5. Up to nine cultivars of each spring crop were planted.

Lime was applied to certain plots in both locations at a rate of 5 tons per acre, while other plots remained un-limed. The liming was done in the fall of 2017.

Through the experiments, Fordyce developed a scoring system to determine cultivar tolerance to acidic soils. The system was based on three different factors. A cultivar was docked if it yielded statistically lower than the top yielding cultivar when averaged across limed and un-limed plots. Similarly, a cultivar was docked if it yielded statistically lower across un-limed plots only; and finally, a cultivar was docked if it yielded statistically lower in un-limed versus limed plots.

“If the cultivar responds to lime, it’s the acidity in the soil that is keeping it from yielding higher,” Fordyce explained.

Cultivars were assigned a number from 1-5. Cultivars assigned the number 1 mean they are susceptible to acidic soils and those assigned the number 5 indicate they are tolerant. Preliminary data from this study has proven interesting. Fordyce has been able to identify three cultivars of canola and two cultivars of field pea that scored tolerant.

Curiously enough, through his research, Fordyce is discovering that field pea and canola cultivars with shatter resistance traits likely have a competitive advantage in low pH soils. This discovery is really important because fields aren’t uniformly acidic, often exhibiting neutral pH on the same field with low pH.

“Plants in soil with a more neutral pH tend to mature more quickly than those in acidic soils, so selecting shatter resistant varieties can minimize shatter loss while the plants in acidic soils are catching up,” Fordyce pointed out.

Fordyce says, there have been years of data from trials with wheat in acidic soils and a genetic marker for aluminum toxicity has been identified by wheat breeders. Fordyce really used previous research performed on spring wheat as a sounding board for his scoring system. So far, his scoring system seems to be right on track. For example, in his experiment, the cultivar Alum, a spring wheat developed specifically for acidic soils, scored tolerant.

When applied to spring wheat, Fordyce felt the scoring system did a pretty good job predicting tolerance when the scores were a 1 or a 5. If the spring wheat cultivar scored somewhere in between, he was less confident in the result.

This lack of confidence, according to Fordyce, simply comes from a lack of data. As previously mentioned, this experiment is only in its beginning stages. As the experiment continues and more data is collected, results will become more conclusive.

The barley portion of the experiment produced somewhat noisier data, so Fordyce was not comfortable presenting any barley recommendations. The hope is that future years of this experiment will yield better results.

Fordyce emphasized, soil at the pH levels he tested, are fairly inhospitable to plant life. If soil pH ever does reach that low, it is cause for remediation. Prevention truly is everything when it comes to dealing with soil acidification. Although growing plants in low pH is less than ideal, Fordyce’s research shows that all hope may not be lost.

“I do think this scoring system is going to allow us to tease out some important findings for farmers who are struggling, or beginning to struggle with acidic soils,” Fordyce said.

There were some logistical hurdles associated with this experiment. The sheer distance between test plots being the most cumbersome issue. Fordyce hopes that with more years, more locations and more data, more results can be procured and used to help farmers as they battle acidifying soils

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