Crop & Pest Report


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Fallout from the Acid Surface Soil Problem in Western No-Till Fields (06/20/19)

The most common problem for our crops in acid soils (pH < 5.2) is aluminum toxicity.

The most common problem for our crops in acid soils (pH < 5.2) is aluminum toxicity. In wheat, the symptoms are poor growth starting early in the season and the roots will be knobby and severely stunted. During the past week, we found that another consequence of acid surface soils can be manganese (Mn) toxicity in canola. The sparse literature on this topic comes from Canada and Australia, where sources indicate that canola is particularly susceptible to Mn toxicity when soils have pH < 5.5. The following images were taken the week of June 16 about 5 miles SW of Minot.

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In the two images, the symptoms may appear similar to S deficiency and K deficiency, but application of those fertilizers with either ammonium sulfate of muriate of potash in two separate areas resulted in no improvement to the canola 2 days after watering them into the soil. According to Foy et al. (1981, Agronomy Journal), screening of cultivars for Mn toxicity should be performed on soils with a pH of 5 to 5.5, which is low enough for Mn solubility to result in toxic conditions, but not low enough that Al would interfere with the screening. The pH of the surface 6 inches of soil in the area photographed was 4.94, indicating the problem is Mn toxicity, with minimal Al interference. The plant analysis of this canola resulted in tissue Mn values over 1,000 ppm, which is at least 20 times the normal value. Aluminum values were over 200 ppm, indicating slight to moderate toxicity.

There are presently studies on remediation of surface acid soils through surface liming in long-term no-till fields being conducted by Ryan Buetow at Dickinson in cooperation with Chris Augustine at Minot.

Dave Franzen

Extension Soil Specialist


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