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Fine points of nutrition affect potato yields, quality

Nov. 29, 2012 | 0 comments

Potatoes can be grown almost anywhere and in all kinds of soil but, especially for commercial and farmer's market growers, attention to the finer points of seed quality and plant nutrition should make a noticeable difference in yields and quality in many cases.

That was the point of a recent webinar on potato crop nutrition sponsored by Spudman magazine.

The presenters were a retired University of Minnesota potato production specialist and two representatives of a Michigan-based company, which specializes in multiple formulation of liquid fertilizers and research on 30 different crop species.

From a background of more than 40 years in the field, University of Minnesota professor emeritus Duane "Sarge" Preston cited a major change in agriculture toward having to carry out sustainable production practices that would gain social and environmental acceptance. He mentioned the use and sharing of water, application of pesticides, aerial spraying, and fumigation as items that growers need to be aware of.

Regarding potatoes, Preston noted that the crop is grown on about one million acres in the United States with average yields running about 425 hundredweight per acre - the highest per acre production for any food crop in the country.

Wisconsin accounts for nearly 63,000 of the nation's potato acres.

Among the factors that growers can control to affect potato yield and quality are the variety grown, seed quality, planting population, moisture (irrigated or not), fertility, timing of the growing season, and pest management, Preston indicated.

Factors beyond their control are soil type, amount of sunlight, wind and humidity, soil temperature during the growing season, and the timing of frosts, he observed.

Potato variety is often dictated by the geographical region and by whom will buy the potatoes (fresh market, chipping, processing, seed), Preston remarked.

He also mentioned the choice of determinant and indeterminant varieties (a concentrated or prolonged period of tuber setting).

Seed management is crucial because of the importance of uniformity in plant emergence, Preston stated. Seed quality depends on a combination of the variety, growing conditions, harvesting method, and type of storage, he noted.

Whether for seed or food, the goal is to "keep good potatoes good," Preston said. For potatoes to be used for seed, he indicated the physiological age - days from harvest to seeding - is an important variable.

Preston outlined planting and harvesting timetables, which could stretch that timetable to 267 days or reduce it to 197 days - plenty of time to make a difference.

He indicated that young seed tends to emerge slowly but produces high yields while old seed emerges quickly but is more likely to result in a crop with both lower yields and quality.

"Knowing how potatoes grow will tell you how to grow them," Preston suggested.

He recommended planting seed that has been warmed into soil with a temperature of at least 45 degrees, being aware of the differences in fertility demand between varieties, taking soil tests to know the basic fertility and plant tissue tests to determine if there are any deficiencies, and being aware that tubers begin to set by three weeks after emergence.

Because the roots control the leaf growth of potato plants, it is important to provide the potatoes with mellow ground, Preston pointed out.

In addition, be sure to leave enough room between the plants so the leaves will be able to capture all of the available sunlight, he noted.

For potatoes, there are three major and 14 micronutrients that affect yield and quality, according to Agro-Culture Liquid Fertilizer (ACLF) agronomy manager Alan Parkinson, who is based in Idaho.

The company, founded in 1983 and based at St. John, MI, was testing 12 new experimental products as part of its research involving 30 crop species in 2,782 trial plots on 580 acres at its main research station in 2012.

For crops ranging from grains to berries to other fruits, Parkinson said there are instances of an oversupply of fertilizer and others in which nutrients are deficient.

Services supplied by ACLF's four regional agronomists (plus a vacant slot in California) include a review of the history of the cropping site, plant tissue testing, residue practices, and manure application, he indicated.

With a business promotional theme of "plants drink, not eat," ACLF specializes in liquid fertilizers of many combinations and release patterns.

For potatoes, one specialty product is a pro-germinator, containing phosphate with a carbon polymer coating, to stimulate rapid emergence and early growth.

ACLF released two new products in 2011 and one in 2012, Parkinson noted. He mentioned such nutrients as magnesium, calcium, and sulfur on how they relate to soil pH, rapid and slow release nitrogen products, and application methods ranging from ground level to airplane spraying.

Because the company endeavors to serve the grower's agronomic goals and to promote environmental sustainability, Parkinson said ACLF's liquid fertilizers are low in salts and contain no chlorine or byproducts.

It has four formulations for primary nutrients and 13 for micronutrients. The company has a Web site at www.agroliquid.com.

ACLF's specialty crops research manager Brian Levene described the results of research projects in recent years with Russet and Snowden (a chipping variety) potatoes in conjunction with Michigan State University and at the company's research site at Pasco, WA.

Among the comparisons were growing potatoes without any additional fertilizer applications, under standards advocated by the Extension Service, with the company's liquid products, and, in one case, with drip irrigation rather than the spray irrigation which was otherwise a standard practice.

Not surprisingly, Levene observed, the trial plots often resulted in yield differences linked to the level and type of fertilization.

Levene cited the methods of fertilizer banding when applied (one inch above the seed piece on both sides of the row as one example) along with foliar treatments with carbon and potassium.

He indicated that per acre applications of more than 200 pounds of both nitrogen and potassium were not out of line.

Levene also stated that the company's liquid fertilizers carry an advantage to granular products because of how quickly both phosphorus and potassium are available to the plants.

Another aspect of the various trials was a separation of potato tubers into weight groupings at above and below 10 ounces and more recently into categories of four to eight ounces, eight to twelve ounces, and above 12 ounces.

Levene observed that use of the pro-germinator stimulant definitely boosted yields and that, as has been indicated by many other soil scientists and agronomists in recent years, that there is now a deficiency of sulfur in the soils in the Midwest.

What has been consistent in those trial plots is a yield advantage of a few to several dozen hundredweights per acre with the higher level of attention to fertilizer needs and the method of satisfying them, Levene concluded.

He noted that ACLF's findings suggest that an enhancement of fertilization beyond the conventional recommendations issued by Michigan State University and other Extension Service specialists is appropriate for potato production.

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