Garden Soil Test - Then what?

Asked October 16, 2018, 8:03 AM EDT

Our garden hasn't been doing very good the last couple years. We put manure on it but that's all. So we're going to buy a garden soil test to test our garden soil. Once we do that and get some kind of results, then what do we do with the results? Do we take those results to a local feed mill and have them look at it and mix up whatever we need to put on the garden? Years ago we sent in a garden sample there and got results back, but we couldn't determine what & how much we needed. When looking at the different things at the public home & gardening stores, they have the 3 numbers listed that they provide, but what about if it is deemed we need a different combination of numbers that is readily available at these stores?

Goodhue County Minnesota soil testing composting nitrogen fertilizer

27 Responses

Thanks for your question. First of all, you are taking a very important step towards a successful garden by having your soil tested. Having said that, I would caution you against using a “home” testing kit. They can be very unreliable. Also, these kits generally tell you little about what type of fertilizer to add and in what amounts. For these two reasons, I would strongly urge you to use the soil testing facilities of the University of Minnesota. While there is a nominal charge for doing this, you will get back a very complete report together with recommendations. If you have a large garden (more than, say, 20 feet by 20 feet), you may want to send in soil samples from two different garden locations. Here is the site that will give you all the necessary information together with instructions for gathering samples to submit:

http://soiltest.cfans.umn.edu/testing-services

This soil testing laboratory gets rather busy in the spring and can lead you to wait several weeks before getting results back. Better to take your soil samples this fall and submit them now. This will help you with planning activities for next spring.

You are absolutely correct in asserting that it may be difficult to find a specific fertilizer that meets the exact recommendations of the soil tests. This happens quite often. This is where we Master Gardeners stand ready to help you. When you get your soil sample results back, take some pictures of them and submit them to this forum. We will assist you in their interpretation and in the implementation of the recommendations.

Good Luck!!

Hey Steve,
Thanks for the info. You noted the exact size of our garden - in square ft. We'll do what you say here... AND I'll get a kit and do that too and compare the results. I can send you that info FYI. After we do this and you can recommend what to put on the garden, then do we go to a feed mill and tell them what we need? Do they mix it all together and then we apply it and then till it in or leave it on top? I'm getting ahead of myself, we can wait on this info if you want. Thanks

Steve,
On a tangent note, I don't know much about how to take care of and maintain our soil to get the most from our gardens and grass. I'm interested in learning about this in all 3 areas, veggie garden, flower garden and grass. Can you offer up anything to help me learn more about this? ...online info, books, maybe classes if it fit into my schedule..... I do pretty good at keeping a good looking lawn but could still learn about the soil. Thanks!

Sorry to bug you again.
What tests do we want to have done on our veggie garden? The form lists a number of different tests;

  • regular
  • salts
  • lead
  • add'l
    • sulfur
    • nitrate
    • boron
    • calcium/magnesium
    • iron, zinc, copper & manganese

Thanks for your questions. I’ll attempt to answer them in the order that you asked them.

1. Once you get the soil test results back, then we can approach how best to meet the recommendations. Most of this will involve action next spring. It is good that you applied manure this fall. Be sure it is worked into the soil before taking a soil sample. Contrary to popular opinion, there is usually very little usable (for plants) nutrients in manure. I don’t foresee a need to go to a feed mill and have a fertilizer specially formulated. In the vast majority of cases we can meet the recommendations in a variety of other ways. For your gardens the objectives will be to apply nutrients in advance of your planting and till things in. This should be done as early in the spring as possible once the soil can be worked. This will probably occur two or three weeks before any planting. The following may helpful to you in the ultimate interpretation of the results:

https://extension.umn.edu/testing-and-analysis/understanding-soil-test-report

2. You might find the following two publications developed by the University of Minnesota to be useful with respect to your grass:

https://extension.umn.edu/planting-and-growing-guides/lawn-care-calendar

https://extension.umn.edu/lawns-and-landscapes/lawn-care

3. Gardening is an ever-learning process. Just when one (I include myself in this category) thinks they know all there is to know, something unexpected arises. It happens to all gardeners. However, you may find the following to give you some information about planning and growing your vegetable garden:

https://extension.umn.edu/planting-and-growing-guides/planting-vegetable-garden

4. In advance of receiving your soil testing results, could you please tell me what kinds of gardens you are considering? Vegetable? Flower? In a general sense, what types of vegetables do you anticipate growing. Same question regarding flowers: what types are you anticipating.

5. I would suggest that you only do the “regular” test. It will provide us with at least 95% of the information that will be necessary. I anticipate that your results will show a high level of phosphorus (part of the regular test). This is usually the case for Minnesota soils. Testing for sulfur, nitrate, boron, calcium, etc., are really not necessary. These elements and compounds are needed by plants in only trace amounts and are typically found naturally in the soil. Related to this, you should take soil samples from your yard, from your veggie garden, and from your flower garden. If you have more than one veggie/flower garden, take you soil sample from the largest of each.

6. A website that we master gardeners use extensively for information is:

https://extension.umn.edu/volunteer#master-gardener

You may want to check it out.

This should be a fun project!

Hi Steve,
We haven't put manure on the garden yet this year. We're going to wait and go with whatever we figure out from soil samples.

To answer your questions...
We have a 400 or so sq ft veggie garden. All we put in it is tomatoes, peppers and a little cucumber. It's used for canning salsa, sauces.... We have had issues with blight in the tomatoes. The last 2-3 years we have not been able to grow green peppers. The plants seem to stop growing after a while and shrivel up some. We use to get awesome green peppers. We still get good chili, cayenne and jalapeno peppers. We rotate the crops.

The flowers we grow are; lilies, rudbeckia, dahlias, allium, cone, hostas, clematis & grasses. Last year we had awesome dahlias. This year was terrible. They didn't grow very big and not all flowered. Plus the damn japanese beetles were hard on em. I read about the japanese beetles coming from grubs and that it takes 3 years to really hit the jap beetles. So I started that this year by putting down an immediate grub killer. Next year in the spring I'll put down season long grub killer and do it again one more year.

Something we've dabbled with to help prevent the rabbits and deer from eating everything is sprinkling milorganite around. We don't do it often enuf to know how well it works. My understanding about that stuff is it's forgiving so you can't really hurt things by sprinkling it generously, just not excessively.

I have to put down lawn winterizer yet. I practice mowing the grass much higher than anyone else. I also need to cut it short for the upcoming winter.

I'll look into those links. Thanks!!!!

Tim












Two quick comments:

If you do not already have a mulching blade for your mower, this might be a worth while purchase. Then consider not raking up the mulched leaves but let them contribute to the organic content of your grass. See:

http://blog-yard-garden-news.extension.umn.edu/2018/10/should-i-mulch-or-bag-my-leaves-this.html

Secondly, dealing with Japanese Beetle grubs is a formidable task. Part of the problem is that even if you rid your yard of all the grubs, you may still see adult
beetles on your plants next season as adults have a flying range of over 300 feet. They will fly in from adjourning yards. There will be two windows of opportunity for dealing with grubs: late May to early June and Mid-July to early August. Treatments during these two periods will involve different pesticides and different tactics.

If you have any evergreens that have a southern exposure to the sun, be sure that you water them well and frequently before the soil freezes.

Cheers,

Yep, we always mulch the grass and leaves. Good reminder on the watering.

I won't be replying now until next week. Me and 10 other guys are going to Lincoln NE for the Gopher fb game. Since 2009 we go to a different Big 10 stadium every year to watch the Gophers. We rent a big RV and a house. The next 2 yrs are the east coast

Your signature says St. Louis cty. You must live in my favorite area, up north near the arrowhead area. Cool. We love the north shore and Duluth and the whole up north area and feel, along w/the BWCA.

I need to get soil samples sent in. Speaking of soil samples, my son in law's brother is an agronomist in SW MN. When I told him about this he wants me to send him a sample so he can send it to the college they use. This should be interesting to see all 3 results, UofM, other college and the kit.

Gotta go get ready for our road trip. Later...

Tim

Talk to you upon your return. Will look forward to the results of the three different soil tests.

Best

Hey Steve,

Got the soil results back from the U. Still waiting on the results from a different college and I have not yet done my in home test yet. But I wanted to get these to you to hear what they mean. The best I can figure after reading them is you go to a store and try to find the closest thing to the 3 numbers and go with that. But that doesn't seem right to me. If possible and it won't cost a fortune, I would like to somehow put down exactly what is needed and do whatever is recommended i.e. till it in or whatever. Of course, this will probably have to be done in the spring now but that's ok. If you can, please first explain in laymans' terms what the problem is in each and then in specific terms and instructions, what we need to do. If this one photo doesn't work for you I can break it into 2. Let me know. Thanks

Thanks for the soil test results. I am going to answer you in two parts: the first dealing with how to interpret the results and, secondly, what action might be taken.

As background you may want to look again at the following publication that I previously mentioned to you:

http://soiltest.cfans.umn.edu/interpretation-soil-test-results-lawn-garden

Let me begin in the upper left corners of your two reports. If you till into the soil your veggie plants after harvesting, this is may account for the rather high (good!) percentage (10.9%) of organic material. If you added manure to your veggie garden, this would also have increased the organic content. The percentage of organic material in your flower gardens should be increased and there are ways to do that. I wonder if you had added manure to your flower gardens? Having high organic levels in your gardens are desirable as this increases water retention, promotes more extensive root development, and contributes various nutrients to the soil. By annual additions of compost to my veggie garden over the past ten years, its organic content is close to 20%

Given the types of veggies and flowers that you grow, the two pH levels are fine.

It is very common to find high phosphate and potassium levels in most Minnesota soils. Your two test results are consistent with this expectation. We may have to devise means by which to increase the potassium content of your flower gardens but even in these gardens the potassium level is acceptable.

Determinations of nitrogen needs in gardens is trickier. Nitrogen in soils essentially exists in two forms: organic and water soluble. The first form is how nitrogen exists in organic (think compost!) matter. This organic nitrogen is not very water soluble and so is not quickly available to plants. Most people may consider compost to be a rich source of plant nutrients. This is generally true except when it comes to nitrogen. The nitrogen recommendations in the two results are for addition of water soluble nitrogen. Gardens need both forms of nitrogen. The nitrogen in organic material is slowly released and gradually builds up the overall nitrogen content of your gardens. The nitrogen that you will add in the form of a fertilizer (next spring) will quickly enter your plants and promote vigorous growth. For more details about soil nitrogen, see the following:

https://homeguides.sfgate.com/ideal-percentage-organic-matter-soil-73408.html

https://extension.umn.edu/nitrogen/understanding-nitrogen-soils#organic-n-sources-760712

In my next email, I will describes actions that you will need to take next spring. To give you a heads-up, I believe that you will be able to satisfy the fertilizer recommendations in a more selective fashion than trying to find a general fertilizer that approximates these recommendations.

Should get back to you again tomorrow.

You have a good percentage of organic material in your veggie garden so that nothing additionally needs to be done other than tilling in veggie remains in the fall. Periodic additions of manure in the fall and tilling it in would also be helpful. This especially should be done for your flower garden as its percentage of organic is somewhat on the low level. Another possibility in addition to manure is to start a compost pile. Perhaps you already have one in progress? If you add leaves, plant debris, and other organic material to the pile in the fall, by the following summer or fall you would have compost to till into your gardens:

https://extension.umn.edu/how-manage-soil-and-nutrients-home-gardens/composting-home-gardens

While compost and manure contain nitrogen, as I mentioned in my last answer, this nitrogen cannot quickly be taken up by plants. So next spring you will need to add a form of nitrogen that is relatively water soluble. This site will give you some suggestions:

https://www.goodhousekeeping.com/home/gardening/a20705698/nitrogen-for-plants/

I especially like the use of ammonium sulfate. Ammonium nitrate is another possibility though it may be difficult to find as its sale is tightly controlled due to its use in explosives. Here is a site regarding ammonium sulfate:

http://www.grasshopperfertilizer.com/ammonium-sulfate-as-a-lawn-fertilizer

Generally, the amount of nitrogen in ammonium sulfate is expressed as a percentage on the label. For example if there is 15% nitrogen in the ammonium sulfate, then a pound of ammonium sulfate would contain 0.15 pounds of nitrogen. Your soil recommendation was for 0.15 pounds of nitrogen per 100 square feet. You would then need to distribute one pound of this ammonium sulfate per 100 square feet. You could work this ammonium sulfate directly into the soil or dissolve it in water and apply it in a liquid form.

Blood meal is another source of nitrogen though its nitrogen will be released into the soil more slowly than ammonium sulfate but generally faster than manure. See:

https://www.wikihow.com/Use-Blood-Meal

Urea fertilizer would be a third possibility. However its nitrogen content can be high, often in excess of 40%, so there is the possibility of it burning your plants. Apply this type of fertilizer by first dissolving it in water. See:

https://homeguides.sfgate.com/quickly-urea-fertilizer-available-plants-83895.html

Lastly with respect to a good nitrogen source for your veggie garden would be to plant nitrogen fixing plants such as peas and beans. After harvesting, the plant remains can just be tilled into the soil. See the following:

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/nitrogen-nodules-and-nitrogen-fixing-plants.htm

There is no need to add phosphorous to either garden.

The flower garden needs some boost in potassium. Potash is often used to meet this deficiency. I have had good success with this. See the following for some ideas:

https://extension.umn.edu/phosphorus-and-potassium/potassium-crop-production

https://homeguides.sfgate.com/much-potash-use-vegetable-garden-45626.html

Most of the above actions, other than fall tilling which is now too late to do, could be taken next spring as soon as you can work the soil and before planting anything.

Good luck and feel free to get back to me with any additional questions.

Thanks for the info. I'll dive into it and get back to you later. Busy time right now.

No problem. Given the fact that your gardens are now most likely frozen, there really is nothing that needs immediate attention.

Hey Steve,

I have yet to immerse myself into all the links and reading but will do so over the winter. Good info but how do I take your info somewhere to go get what we need and know how do I know how much to put on? In other words;

1. Where do I go to buy what? Can I go to a garden center and show them the test results and ask for the ingredients we need? Or a feed mill?
2. How much of each do I need?
3. How thick do I put it on each area? I have a broadcast spreader and hand sprayer.

This is the info I'm looking for come spring.

The garden size is 600 sq. ft. and the flower area is 300 sq. ft.

Thanks!

Tim

To answer your recent questions, there are two possibilities: the quick and easy approach and a more detailed approach.

The quick and approach is to use a common garden fertilizer known as 10-10-10. It consists of 10% nitrogen, 10% phosphorous, and 10% potassium. In one pound of this fertilizer, there are 0.10 pounds of nitrogen, 0.10 pounds of phosphorous, and 0.10 pounds of potassium. Using six pounds of this fertilizing in your veggie garden and three pounds in your flower garden would, more or less, meet the recommendations. While not exact, and considering you are adding phosphorous, no significant harm should be done.

However, you previously indicated that as much as possible you wanted to match the recommendations from the soil test. It is extremely unlikely that a garden center would be willing to prepare two different fertilizers (recall the recommendations for your two gardens are different). I would then suggest that you use individual nutrient applications.

Apply nutrients twice during 2019 since the soil test recommendations were on an annual basis. You should fertilize the gardens in the spring about a week or two before planting or before significant flower growth is seen. At that time about 2/3’s of the recommended annual amounts would be added. Then during mid to late June, the other 1/3 of the recommended annual amounts could be added. In both cases spread things by hand, work gently into the soil, and water well. Doing these two applications before impending rains would be ideal.

To meet the nitrogen requirements use ammonium sulfate in both gardens. You should be able to purchase this in any garden center. In the presence of water and oxygen in the soil, ammonium and sulfate are decomposed by naturally occurring microbes. During this process, nitrogen and sulfur compounds are released into the soil in forms that plants can take up. Nitrogen and sulfur are elemental nutrients required by most plants. Plants require nitrogen to synthesize chlorophyll and other important components of leaves, stems, and roots. Without enough nitrogen, plants turn yellow and fail to grow. The presence of this element makes for a lush garden, full of plants with strong stems and leaves. Your soil tests said nothing about sulfur but no harm will be done by adding it. Plants use sulfur to produce proteins, amino acids, enzymes and vitamins. It also helps the plant's resistance to disease, aids in growth, and in seed formation. The ammonium sulfate you purchase will specify percentages of nitrogen and sulfur. I just looked at the ammonium sulfate that I use and it contains 21% nitrogen and 22% sulfur.

Your veggie garden is approximately 600 square feet so you will need a total of approximately 0.9 total pounds to nitrogen. A little over 4 pounds of ammonium sulfate (21% nitrogen) would meet this requirement. Apply about three pounds in early spring and then slightly more than one pound in late June.

Your Flower garden is approximately 300 square feet so you will need a total of approximately 0.45 total pounds to nitrogen. A little over 2 pounds of ammonium sulfate (21% nitrogen) would meet this requirement. Apply slightly more than one pound in early spring and then about a one pound in late June.

If the ammonium sulfate you obtain has other than 21% nitrogen, you will have to adjust these amounts. If you encounter difficulties in so doing, be sure to let me know.

Another possibility for adding nitrogen is to use blood meal. It typically contains about 12% nitrogen. So a pound of blood meal would contain 0.12 pounds of nitrogen which is pretty close to 0.15 pounds. You would need about six pounds of blood meal for your veggies and about 3 pounds for your flowers. Add four pounds to blood meal to your veggies in early spring and then two pounds on late June. Add two pounds to blood meal to your flowers in early spring and then one pound on late June.

To meet the potassium requirement of your flowers, use potash. You should be able to purchase this in any garden center. Potash is a form of potassium oxide. Potassium is vital to plants throughout their life cycle. Potash is water soluble and its potassium is easily absorbed by plants to help them flower and produce seeds. The calculation here is quite simple as the flower recommendation is in terms of potash (0.3 pounds per 100 square feet) and not potassium. You will need to add 0.9 pounds of potash to your flowers; 0.6 pounds in early spring and 0.3 pounds in late June.

Give me a shout-out if you have any questions. Have a good holiday season.

Hi Steve & Happy New Year!
I finally got around to carefully re-reading your replies on what to do for our gardens soil. I think I have it dialed in but let me throw it back to you to verify.

To begin, apply approx. 2/3 of recommended amts 1-2 wks before planting. We usually wait til Memorial Day or right after to plant so that means apply 2/3 of supplements mid to late May. Apply remaining 1/3 late June.

We only need to purchase 2 things, ammonium sulfate (nitrogen min. 21%) and potash (potassium) in the amounts of 7-8lbs AS and 1lb Potash.
Veggie garden - apply approx. 3.3lbs AS in mid/late May, 1.7lbs late June
Flowers - apply approx. 2lbs AS and 0.7lbs Potash in mid/late May, 1lb AS & 0.3lbs Potash late June

Is that it? How did I do in translating your info?





Tim: Your interpretations are spot on. Please keep me posted as to how your two gardens progress during 2019.

Stay warm,

Hi Steve,

It's been a while........ I bought the necessary items we discussed here and am going to put them on the beds this weekend. I'm assuming these should be tilled in if possible, right?

We are thinking about giving our veggie garden a year break and plant it again next year. We're not sure yet, but leaning this way. If we do that, along with adding the needed minerals discussed here, how should we handle the garden ground this year so we can use it next year? I mean, if we do nothing to it, weeds and grass will take it over. Is there some kind of ground cover that we should put on it to prevent or minimize weeds and grasses from taking it over?

Steve,

I just re-read some info you posted here and found the answer to the tilling question. You said to work it in by hand, got it. Thanks. FYI - I bought the 2 nutrients from Gertens.
Thanks again Steve. I really appreciate your assistance.

Tim

Wait Steve. What about the ground cover question?

Tim:

Sorry about the delay. The server on this website has had some recent issues and a boundary waters trip consumed some of my time.

I use an annual ground cover in my own veggie garden and plant it in the late summer/early fall. I favor a ground cover such as clover as it will enhance the nitrogen content of the soil. This can be an important function of a ground cover. I then remove it in the spring when I plant my veggies. This ground cover then can prevent annual weed seeds from germinating in the spring. This is a second important function of a ground cover.

Take a look at the following:

https://homeguides.sfgate.com/clover-alternative-groundcover-74639.html

I really am partial to clover but do use an annual variety of it. This way I know that it will not subsequently compete with my veggies.

See:

https://www.hunker.com/13426433/when-to-plant-clover-seeds

As you can see from this site, now would be a good time to plant the annual clover. Bees will love you for this. Most garden centers will carry clover seed

As to type, my preference is white clover. Just one slight drawback. Clover is a favorite food of deer so that might be an issue.

Again, sorry for the delay.


Hi Steve,

No problem with the delayed reply. It's all good.

A BWCA trip?! I'm jealous. Good for you. Where did you go? We try to go every other year or so. We don't go in far tho. It's a magical area. I love it. I've subscribed to the Boundary Waters Journal for years.

Clover sounds perfect! Thank you!

Went in from Sawbill (north of Tofte) and trekked up to Cherokee Lake. Good lake trout fishing. A bit chilly around the edges.

With respect to the clover and if you plant it now, just let it do its thing over this summer. If you use annual clover, it will start to droop a bit come this September. Wait until after the first frost and then work what's left of the clover into the soil. During this summer it will have put nitrogen into your garden and then as it rots down over this coming winter, it will add organic matter to the soil. If all goes well you should be in great shape come next spring.

Have a great spring day!!




















Steve,

I accidentally purchased perennial white clover. Can we put that down? Now my wife changed her mind and we put in tomatoes and some pepper plants. Here's what I'm thinking, please tell me if I'm wrong. We can still put down this perennial clover around our plants and let it grow. At the end of the year we till it up anyway, so the clover will add nutrients to the garden. If it comes back up next year, we clear spots and plant in it. Would that work?

Don't see any problem with using the perennial white clover. Tilling it up this fall would work. By using perennial white clover there is a greater chance that you will see more clover in spring 2020 but it would also be easy just to pull things up at that time.

Good luck!!