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Crop advisor casebook: Pigtailing barley presents a problem

A Crop Advisor's Solution from the July 16, 2019 issue of Grainews

Sara Stagg.
photo: Supplied

Dwayne farms around 4,500 acres of red spring wheat, canola and malt barley near DeBolt, Alta. He gave me a call late last June because of a recurring problem in one of his barley fields.

When visiting the field, I found some barley plants located in a concentrated area — around five acres — had severe pigtailing of the leaf tips. This symptom is often associated with a copper deficiency. The rest of the plants in the field were asymptomatic and not showing signs of nutrient deficiency.

Both Dwayne and I knew that pigtailing in barley plants is a symptom of copper deficiency. What we didn’t understand was why the plants in this five-acre area were the only ones exhibiting symptoms.

We took tissue samples from symptomatic and asymptomatic plants as well as soil samples from the affected and unaffected areas of the field to investigate why the pigtailing was limited to such a small area.

Dwayne was implementing a balanced macronutrient fertility program. We also checked his herbicide application records to confirm no residual products had been used on this field, eliminating the possibility that we were dealing with carryover issues.

Dwayne’s barley crop had severe pigtailing of the leaf tips. It looked like a sign of copper deficiency. (l) Lab results showed an extreme copper deficiency in symptomatic plants, but why were the symptoms plants limited to a five-acre area? (r)
photo: Supplied

The plants in Dwayne’s field looked very sick. Lab results from the tissue test were several days away and Dwayne felt confident enough in the diagnosis to make a decision to act to save the unhealthy crop without a confirmed copper deficiency test.

Dwayne sprayed the entire field with a very low rate of foliar copper to help the plants along as the crop was at the flag leaf stage and the head was about to emerge. However, this did not solve the bigger riddle: why were the severe symptoms isolated to those five acres?

The lab results from the affected and unaffected areas of the field were very interesting. Soil samples from both areas indicated a copper deficiency. The results of tissue samples taken from the symptomatic barley plants indicated an extreme deficiency and the tissue samples from asymptomatic plants revealed copper levels were very low to deficient.

However, it was the soil’s organic matter and iron content numbers that stood out. This data was the final piece of the pigtailing puzzle.

Crop Advisor’s Solution: Soil organic matter and iron concentration affect copper

The test results of the soil and tissue samples indicated a copper deficiency across the entire field. The results of tissue samples taken from the symptomatic barley plants indicated an extreme deficiency while tissue samples from asymptomatic plants revealed copper levels were very low to deficient. In the end, it was the organic matter and iron content in the soil samples that provided insight to the variability across the field.

Organic matter holds and stores nutrients that are later released to plants. The soil organic matter of the area of the field in which the plants were exhibiting symptoms was 11 per cent. The soil organic matter of the area of the field in which the plants were asymptomatic was 7.5 per cent.

The plants in the affected area were likely unable to take in enough copper due to the low concentration of the positively charged copper in the soil and the strength of the bond to the negatively charged organic matter.

The soil sample results also indicated a high iron concentration in the area where the plants were showing visible signs of deficiency when compared with the area where plants were asymptomatic.

Like copper, iron is positively charged and competes in the soil for exchange sites and the ability to enter plant roots. In this scenario, a combination of the low copper concentration in the soil, the interaction between copper and iron after a rain event and the high organic matter content inhibited the plants from extracting enough copper from the soil.

Copper deficiencies in barley can severely impact yield. Moving forward, Dwayne will take more consideration of micronutrients in his fertility program and will proactively soil test and apply soil applied micronutrients when required.

Sara Stagg, BSc, works at Richardson Pioneer Ltd. in Lavoy, Alta.

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