Posted by: HortAlaska | May 20, 2014

Fertilizer overload

I was in Anchorage over the weekend, and I stopped by the Alaska Garden and Pet (Mill and Feed). They had a snazzy poster advertising Arctic Grow Peony Blend with minors. I talked to the woman behind the counter, and she told me the recommend rate is 1/2 cup fertilizer per plant. That is so impressively huge, I would like to find out where that recommendation came from. I contacted the soils people here, and Bob VanVeldhuizen did a little math. He took some pictures of what that level of fertilizer would look like, and he also made a rough guesstimate of how many pounds per acre that amounts to. For most of our garden we use about 500 lb per acre 10-20-20 as a general application once a year. Bob’s illustration shows about half that- -a recommendation for grains. If you apply 1/2 cup per plant around about a 6 inch diameter hole for a peony root, he estimates that recommendation will amount to almost 18,000 lb per acre! Not only is that way too much fertilizer, those roots haven’t even established their fine feeder roots, so most of the solubles will be lost to leaching into the soil. I saw a whitish ring of fertilizer on top of the soils in some peony fields last summer and a lot of shoot death.

I have very fertile soils, and for the first five years, the peonies at the GBG got NO extra fertilizer except what was in the ground. I am certainly not advocating that route, but the 1/2 cup per plant can burn fine feeder roots, cause such high salt levels in the soils as to kill those big storage roots, waste money, and cause problems with groundwater. This fertilizer also has micronutrients, but I couldn’t figure out how much. Micronutrients at high levels can cause toxicities that can last for many, many years. I usually apply approx. one tablespoon of 10-20-20 per plant to mature plants. On new soils that would be higher, but 1/2 cup? Not!

Fertilizer rate photos

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