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| Carl Rosen |
There are 17 elements that are considered essential for the growth of potatoes, almost half of which are micronutrients. In his presentation to delegates attending the recent Manitoba Potato Production Days 2005 and the 33rd Western Potato Council conference and trade show in Brandon, Manitoba, University of Minnesota professor and extension soil scientist Carl Rosen identified each of the micronutrients and provided thumbnail sketches on them.
The micronutrients that Rosen discussed include zinc, boron, chlorine, copper, iron, manganese, molybdenum and nickel. Most soils, he noted, contain sufficient amounts of the micronutrients for healthy plant growth.
It has only been in the past 10 to 15 years that nickel had been considered important for plant growth, he noted. Very low concentrations of nickel, chlorine and molybdenum are required for plant growth, he noted.
Boron plays a role in carbohydrate transfer and cell membrane integrity. Copper, zinc and manganese are important for enzyme activity. Copper and iron play a role as well in electron transportation. Copper is also important in cell wall formation, while iron aids chlorophyll photosynthesis. Manganese helps with energy transportation and fatty acid synthesis.
Rosen said that he has never seen deficiencies in the field of chlorine, copper or boron – although the latter could become deficient in sandier soils or high temperatures during times of drought.
“I have seen cases of boron toxicity,” he said. “The characteristic signs are cupping leaves and marginal scorching. The treatment is with good quality water. It’s a problem that is more common in Ontario than the West.”
He reported that some potato varieties – such as Norland – are more susceptible to iron deficiency than others. Iron deficiency can be a problem in saturated soils where alkaline P2 levels are low.
The signs of manganese deficiency are interveinal sclerosis of younger leaves with a fishbone appearance on the leaves as well as yellowing and brown spotting between the veins. The problem generally occurs in alkaline or organic soils. The solution is to increase the ph levels.
“Too much manganese can also be toxic,” Rosen said. “The availability of manganese can increase dramatically in acidic soils. The only answer is to lime the soil.
How can a grower know if his soil is deficient in one or more micronutrients? You can do a tissue analysis or try visual observations. The first step, Rosen said, is to conduct a soil analysis.
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