How to Find the Best Fertilizer

Researchers seek the best program

Published in the January 2013 Issue Published online: Jan 23, 2013
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Maintaining a healthy leaf canopy is critical to potato production. In short, healthy leaves last longer. The longer they last, the better the yields. Fertilizing potatoes properly not only promotes healthy leaves, it also influences overall plant health and promotes resistance to insects and diseases. This translates to better quality crops and optimum yields.

Choosing a Fertility Program

When trying to find the best fertilizer for potatoes, start with a good soil test. Soil test results indicate soil salinity, acidity (pH) and fertility.

Choosing the right fertilizer blend is much easier when you know the nutrient requirements of your planting site.

Once you know your site's nutrient needs, consider what fertilizer will be the best fit. This step is important because nutrients play such a critical role in maintaining healthy potatoes. Phosphorus, for example, influences metabolic processes such as the transportation of sugars through potato leaves and the conversion of sugars into starch. Potatoes also require higher amounts of nitrogen and potassium prior to and during tuber bulking.

In 2011, researchers at the North Central Research Station, owned by Agro-Culture Liquid Fertilizers, compared the marketable yields from multiple potato fertility programs. Their goal was to determine if programs or individual fertility components have a greater impact on total yield and size of potatoes. To do this, they evaluated the performance of various combinations of Agro-Liquid products with that of conventional fertilizers (Figure 1).

Growers broadcast the dry fertilizers into their treatment areas in early May. They split the liquid fertilizer planter treatment into two bands; placement was two inches above and two inches to each side of the seed piece. The potato cultivar used for the experiment was Russet Norkotah.

Two side-dress nitrogen applications took place throughout the growing season. The first application occurred at hilling, the second one 10 days afterward. Harvest took place in early September. Researchers used potatoes larger than 1.5 inches for evaluations. They sorted them according to size/shape and then weighed each grade to determine yields.

Research Results

"Figure 1. Fresh market potato fertility programs utilizing various sulfur products and fertilizer combinations to impact yields and sizing, 2011.
"Figure 2. Marketable yields from multiple potato fertility programs in 2011. Bars are stacked on the basis of potato size and are ordered to match treatments shown in Figure 1.

The Agro-Liquid-based programs performed well and their yields were higher than the conventional fertility programs (Figure 2). Sometimes changing one part of a particular program had a positive impact on yields. This was the case with Treatment 3, which was a combination of conventional sources of nitrogen and potassium, but Pro-Germinator replaced 10-34-0 at time of planting. Among the conventional-based fertilizer programs, this treatment had the highest yields.

Treatment 7 was a mix of S-Calate with Agro-Liquid based products. This modification worked well, as Treatment 7 had the highest yields overall. In addition, the quantity of potatoes in both grade categories increased over the Agro-Liquid base (Treatment 4). Data from Treatments 2, 6 and 7 shows the value of adding sulfur to the blend, but "inert" ingredients can be just as important.

Research results provide some valuable insights for growers who are trying to find the right fertility program for their potatoes. Generally, the Agro-Culture Liquid Fertilizers' programs proved to be a better option for increasing yields than the conventional fertilizer programs. To see the full research results, refer to the 2011 Research Report, Fresh market potato (Russet Norkotah) soil fertility program comparisons (NCRS 11-201).