Soil pH is the big elephant in the field

Across Western Canada there are roughly 20 million acres affected by low soil pH. To put this in perspective, this is more than all the land farmed in Indiana or the United Kingdom, and ten times all the farmland in the Netherlands. In Indiana, the UK and the Netherlands, the first thing a grower looks at on a soil test is pH. 

Within the higher pH areas, there will be many fields with significant portions of low pH, according to a large volume of sampling. 

Low soil pH is due to a number of factors low pH parent material, organic matter breakdown and nitrogen fertilizer. It's just a natural consequence of growing crops.

My question is…why not here? We know that pH affects pretty much everything crop growth, nutrient efficiencies, herbicide carryover, clubroot risk and, when limed correctly, the positive effects can last for upwards of 10 years.  

Yet, we are still hesitant to tackle the elephant. Cost is the most likely cringe factor. However, a number of factors have changed, making liming a more economic option. These include VR capabilities of the application equipment and the availability of alternative liming sources.

If you have a field with a pH of 5.8, you can be sure that parts of the field are pH 4.8 and other parts are pH 6.8. This means that 20-40 percent of the field likely has a pH low enough to negatively affect yield potential, nutrient use and water use.  

In very simple terms, this means that 20-40 percent of the 20 million affected acres need liming. Obviously variable rate liming makes tremendous sense.

This spring, agri-coaches Matt Gosling and Andrew Clements, owners of Premium Ag Services Ltd, grid sampled a 477-acre field near Calgary. The pH (0-6") on this field ranged from 4.4 to 7.7. Doug McKay, geo-coach with Cervus Equipment Corp. out of Calgary, built the prescription map for the spinner floater with VR capabilities and a by-product lime material was VR applied across the field. The range of VR lime application was 0 to 8,600 pounds per acre with about 21 percent of the field receiving little or no lime.  

The beauty of liming in this manner is that while it is VR, it doesn't have to be precise. If we get close and improve the pH issue by 80 percent, the ramifications are huge.

Here's my rough ‘napkin math' for this situation:

A responsive crop such as barley should have 30-50 percent more yield potential and grow at least 30 percent more crop on the low pH areas. Plus, there is the increased nitrogen, phosphorus, potassium and sulfur fertilizer efficiency, so factor in at least a $20 nutrient benefit. Increasing pH will reduce micronutrient availability.

In one specific case over 50 percent of the field showed impressive responses:

•Barley – 30+ percent yield potential increases – say 27 bushels for this farm at $4.50 = $120 – total = $140

•Canola – 20 percent – say 9 bushels at $10 = $90+ $20 = $110

•Wheat –15 percent – say 11 bushels at $7 = $77 + $20 = $97

•Peas –30 percent – say 18 bushels at $4.72 = $85+ $20 = $105

Conservatively, this is an additional $100 crop revenue averaged across crops. If we assume the effect lasts 10 years, that's $1,000 per acre for a $107 per acre investment. If you think it's closer to five years, we are still talking about a 5+:1 payback.

To summarize, here is my advice: Don't ignore the elephant in the field any longer! Tackle it head on it's a fix that keeps on paying back.

Elston Solberg is the director of Agri-Trend's Agri-Knowledge Division.


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