During the 41st Annual Idaho Potato Conference held in conjunction with the 30th annual Ag Expo at Idaho State University in Pocatello, spud growers were coached at well-attended sessions on how to reduce their fertilizer expenses, which vaulted and then retreated somewhat in 2008.
“Regardless of what the cost is going to be, it’s not going to be low” in 2009, Jeff Stark said during a workshop titled “Hooked on High Fertilizer Rates? Time to Break the Habit.” Stark chairs the horticultural services division of the University of Idaho’s Idaho Falls R&E Center.
The efficiency of nitrogen and phosphate fertilizers depends on the target, soil condition, and limiting factors, Stark said. If new treatments are applied at inappropriate times, yields can be reduced, having a deleterious effect on potato quality, he added.
Dr. Bryan Hopkins, an environmental scientist at Brigham Young University in Provo, Utah, said nitrogen is the most important element for potato growth. “We don’t see much benefit to phosphorus at all” for the short term, he said. The earlier nitrogen fertilizer is applied, the more likely growers will lose it. He recommended it be applied no sooner than 35 days after seed is planted.
By the 50th day after planting, tubers start to grow, consuming about 50 percent of the nitrogen. By the 75th day, most of it has been absorbed by the plant. By the 90th day, the nitrogen leaves the vines, going into the tubers. Between the 35th and 85th days after planting is when the nitrogen needs to be delivered to the plant, Hopkins recommended. “Put fertilizer where it needs to be and lay off where it doesn’t need to be.”
“Fertigation,” or applying fertilizer in irrigation systems, is time-consuming and more expensive than traditional ways of applying it, Hopkins said. Slow-release fertilizers haven’t always worked as well. Polymer-coated or encapsulated fertilizers do not move with water as readily.
Research in Eastern and South Central Idaho shows it’s important to apply fertilizer at the time of a plant’s emergence, the BYU professor said.
“At a Maximizing Your Fertilizer Dollars” session, Hopkins said fertilizer prices are at a temporary low, but will go back up with natural gas and petroleum prices. The biggest impact on fertilizer prices will be a demand increase in China and India, which he said “are going crazy agriculturally. … To this day, all the fertilizer spread in these two countries is spread in bags.” That will change as they modernize, he said.
Most growers, he said, under-manage and over-fertilize their crops. Farmers with the highest yields are not usually the ones with the highest profits, Hopkins said, advocating more moderate rates of fertilizing, citing the law of diminishing returns. “At this point, it’s no longer good to throw money at it. … Apply inputs only when it’s reasonable to expect more return than cost.”
Paraphrasing Charles Dickens, Dr. Joe Guenthner, extension economist for the University of Idaho, said these are the best and worst of times for Idaho’s potato industry. While spud prices have climbed, so have costs for fuel, fertilizer, property, and other inputs. He predicted Idaho potato growers could be in for more chills and thrills in 2009, noting they paid record high prices for fertilizer in 2008.
Marieke de Rijke, an assistant vice president and industry analyst with Rabobank International, a food and agribusiness research and advisory corporation based in The Netherlands, said fertilizer costs are a very important influence on the potato sector. Although wholesale fertilizer prices have come down, farmers haven’t really seen it, she said.
About 1,150 people attended the Idaho Potato Conference this January, up 200 from 2008, said Dr. Nora Olsen, conference chairwoman.