Fertilizer 33-0-0 #747822 - Ask Extension

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Fertilizer 33-0-0 #747822

Asked May 03, 2021, 8:05 PM EDT

We had our soil tested by the U of M this spring. We have a few fruit trees and tiny garden. It said we needed to use a fertilizer that was 33-0-0. I cannot find that anywhere. Where can I purchase it? Or what else can I use? TY

Carver County Minnesota

Expert Response

Hi Joan and thanks for the question.

So that I can give you a good answer, might it be possible to take a pic of the front side of the soil report?

But also to answer your question, it is possible to find, with difficulty, 33-0-0 fertilizer. 

Looking forward to your response and providing you a more complete answer.

Enjoy these wondrous gardening days!!



Steve Hedman Replied May 03, 2021, 9:42 PM EDT

I found nitrogen only fertilizer at Amazon, but it was 39-0-0.

joan anderson Replied May 04, 2021, 11:28 AM EDT

The reason you are unlikely to find pure 33-0-0 nitrogen fertilizer is because it is used in explosives and somewhat restricted.  Nitrogen is highly mobile in the soil meaning it washes out easily unless it has an additive to slow the release.

So look for a slow release nitrogen. Also adding too high a concentration during the active growing season can burn plants.  Farm suppliers may have higher concentrations but there may be specific knowledge needed to apply them correctly.

Your local garden center should be able to help with the selection they have available.  Online products are also available as you noted. The third website is just one example of a slow release fertilizer.  There are others. It has a higher than 33-0-0 ratio (39-0-0) so you would spread it over about 20% wider area than recommended to reduce the concentration. 

See:  

1.https://www.canr.msu.edu/news/nitrogen_cycle_and_nitrogen_fertilizer_sources_part_1

2. https://www.canr.msu.edu/news/nitrogen_cycle_and_nitrogen_fertilizer_sources_part_2

3.  https://www.greenwaybiotech.com/products/nitroform-39-0-0

Marykay Haas Replied May 07, 2021, 12:01 PM EDT

Hi Joan,

It is a very busy time for us here and I see that another Master Gardener last responded to you. I am appreciative of that. Let me just elaborate more on your situation now that I have seen the soil test report:

1). The organic content (5.5%) is satisfactory though slightly low. At least in your garden consider adding some compost in the fall. Doing so now will not have much of an effect.

2). The soil pH of 7.7 is a bit on the high side of being acceptable. Again this fall, besides the compost, mix in some peat moss. This will tend to gradually lower the soil pH.

3). If you get the 39-0-0 fertilizer, you need to be mindful of what my fellow Master Gardener said. Adding too much nitrogen can cause you problems. Note that your soil test said to add 0.07 pounds of nitrogen per 100 square feet on AN ANNUAL BASIS. You would not add this all in one application. 39-0-0 fertilizer means that for every pound of fertilizer, there is 0.39 pounds of nitrogen. This would then calculate p to add about 0.17 pounds of this fertilizer for every 100 square feet. But you need to do this in two separate applications: one now (0.085 pounds of fertilizer) and one late this summer (another application of 0.085 pounds of fertilizer). This is really splitting hairs considering that you seem to be dealing with a rather small area. Buying a large bag of 39-0-0 of which you will only use a small amount doesn’t make much sense. Again as my Master Gardener colleague suggested, you should look for a slow releasing nitrogen addition. Slow release simply means that it gradually dissolves in soil water and thus provides nitrogen over a period of time. Applying a single application of a slow release nitrogen now should carry you through this season so no fall application would be necessary. That gardener also provided you with some good ideas as to possibilities. In applying any of them, be sure to read the label on the product carefully with respect to application rates. The amount of nitrogen recommended to you for adding is rather small and perhaps could even be met by the fall application of compost that I suggested.

Good Luck!!

Steve Hedman Replied May 09, 2021, 4:14 PM EDT

Hi Joan,

It is a very busy time for us here and I see that another Master Gardener last responded to you. I am appreciative of that. Let me just elaborate more on your situation now that I have seen the soil test report:

1). The organic content (5.5%) is satisfactory though slightly low. At least in your garden consider adding some compost in the fall. Doing so now will not have much of an effect.

2). The soil pH of 7.7 is a bit on the high side of being acceptable. Again this fall, besides the compost, mix in some peat moss. This will tend to gradually lower the soil pH.

3). If you get the 39-0-0 fertilizer, you need to be mindful of what my fellow Master Gardener said. Adding too much nitrogen can cause you problems. Note that your soil test said to add 0.07 pounds of nitrogen per 100 square feet on AN ANNUAL BASIS. You would not add this all in one application. 39-0-0 fertilizer means that for every pound of fertilizer, there is 0.39 pounds of nitrogen. This would then need to add about 0.17 pounds of this fertilizer for every 100 square feet. But you need to do this in two separate applications: one now (0.085 pounds of fertilizer) and one late this summer (another application of 0.085 pounds of fertilizer). This is really splitting hairs considering that you seem to be dealing with a rather small area. Buying a large bag of 39-0-0 of which you will only use a small amount doesn’t make much sense. Again as my Master Gardener colleague suggested, you should look for a slow releasing nitrogen addition. Slow release simply means that it gradually dissolves in soil water and thus provides nitrogen over a period of time. Applying a single application of a slow release nitrogen now should carry you through this season so no fall application would be necessary. That gardener provided you with some good ideas as to possibilities. In applying any of them, be sure to read the label on the product carefully with respect to application rates. The amount of nitrogen recommended to you for adding is rather small and could even be met by the fall application of compost that I suggested.

Good Luck!!

Steve Hedman Replied May 09, 2021, 4:19 PM EDT

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