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jodikay_gw

soil test question

14 years ago

I recently had a soil test done thru the Univ of MN. The soil texture is coarse and the ph was 8.0. It is lacking the N and I don't need P/K. Research is suggesting I need to add sulpher to lower the PH but everything I have read says this is a very slow fix. My organic matter is 19.2% which is good.

So my question is, do I really need to go the sulpher route and if so, when should I amend the soil?

What other options do I have? Do I really need to lower the PH? Is having a 8.0 PH that bad for growing vegetables?

Thanks for any input,

Jodi

Comments (19)

  • 14 years ago

    8.0 is excessive to almost everything you'd want to grow...except apples.

    You're shooting for a 6.0-6.5 for ideal production of almost everything (except blueberries...and tobacco).

    Unfortunately, it's a whole lot quicker to raise your soil pH than to lower it...and 8.0 to 6.5 is a ways to go.

  • 14 years ago

    If your soil organic matter is 19% your soil will test acidic. But it shouldn't matter. Plants aren't sitting with a meter saying they wish the soil was a more neutral pH. It has to do with nutrient availability. With very high organic matter content you will have very high nutrient availability regardless of the pH. A better test in some ways is to look at your plants if they are thriving and healthy that is what is important. I'm guessing that perhaps you are using lots of leaves, which is good. But to increase nitrogen you might want to try manures or compost to bring your nitrogen levels up. The soil test might read low in nitrogen again because of your high ogm. It might be that your not low or short in Nitrogen it just wasn't available to be read. Again how are your plants faring might be a better test.

  • 14 years ago

    pH is directly tied to nutrient availability and/or toxicity.

    It's not the pH of the soil that's directly causing plants to suffer as much as it's how locked up some elements/nutrients are vs. how over-available others are depending on the soil chemistry at a certain pH.

  • 14 years ago

    Also...while 6.0-6.5 is an ideal pH...there is nothing wrong with planting while you're adjusting your pH. You will probably suffer some low yields until you get into the 7.0-7.5 area, though.

    The problem in my area is acidic soil. I lime my soils to adjust to 7.0 rather than 6.5. While 6.5 is ideal (imo), the benefit isn't large enough to lime every season trying to keep a narrow 6.0-6.5 range. If I lime to 7.0 initially it will give me a year+ more between adjustments.

  • 14 years ago

    I should add that I lime to a 7.0 (all done via calculation and it's probably closer to a 6.8-6.9 in actual practice) before the winter crops when I adjust because almost all the cool season stuff does well at a higher pH. By the time the winter rains and a little time has passed it's probably settled into a 6.6-6.8 area.

    Every soil type (parent materials) and the amount of moisture it gets is going to influence how the pH changes.

    Not all basic soils are created the same. Adding sulfur in MN works because it cleaves off H+ (acid) ions that are being held, unexchangable/unavailable...adding just sulfur in basic soils in some parts of the US South-West can be a losing end-game if the soils are high in calcium because once the H+ ions are cleaved off by reacting with the sulfur they almost immediately team up with the calcium to remain in your soil...leaving the pH unchanged.

  • 14 years ago

    pH is a representation of the concentration of hydrogen ions in a given solution, in this case, soil. When pH is high, micronutrients like iron (Fe- which is negatively charged) are bonded to the positively charged hydrogen ions. Remember back to high school science where opposite charges repel, and opposites attract and bond. The reason why blueberries like an acidic soil is because they need more iron than other plants, and iron becomes MORE available the lower the pH, since it's charge is negative.

    Now, with other garden plants, a high pH will lock up other nutrients as well, that's why pH adjustment is critical.

    Fast acting sources of sulfur which will lower your pH quickly include aluminum sulphate and iron sulphate, you can find charts online which will tell you how much to apply over a certain size area. You want to bring your pH down to 6.2 - 6.8, in that range, the nutrients in the soil will be the most available, it has to do with each nutrient's charge.

    Inorganic sources of fertilizer lower the pH of a soil over time, which is why you never hear of a farmer putting on sulfur, they are always applying lime to raise the pH. Diammonium phosphate, urea, ammonium nitrate, and anhydrous ammonia all work in the soil to lower the pH, just to name the most common ones.

    I have the same problem, I have deep prairie soils that formed under limestone bedrock, and I am constantly fighting high pH numbers. You can add sulfur if you like, but a better approach would be to kill two birds with one stone and give your soils some phosphorous or nitrogen while you are lowering the pH. Remember to look up all the recommended rates though!

  • 14 years ago

    Thanks for all the input. Overall, my vegetables are not doing that bad. Between too much rain, not enough rain, insects and likely some mistakes on my part, some of my yields were not good. However, I am not a farmers daughter for nothing, as there is always next year!

    Jodi

  • 14 years ago

    It is not true that 8.0 is too high for most veggies. All brassica (from arugula to brussels sprouts), cardoon, spinach, chard, beet, lettuce, chicories, garlic, onion, asparagus will all do very well. You may consider adding sulfur to only half your beds, and use those for summer fruiting plants and potatoes. If you add sulfur now the garden will be ready in spring. Also mulching with wood chips, which have a pH in the 5-5.3 range, helps temporarily, and on top of that chips are free and eliminate weeding. For this year it is too late to add anything, but your Fall garden will not suffer as fall vegetables are OK with high pH.

  • 14 years ago

    I would add sulfur to lower it. Some vegetables don't mind it that high as mentioned above, but most don't like it, and if you get it between 6-7, almost all vegetables grow well there. Sulfur usually takes about 6 months to work. You can use the faster acting ones, but you can still grow decently in the meantime, especially with the high organic matter that does tend to help with pH uptake issues somewhat.

    Mixing in pine bark can help with pH, and is a good choice if you have drainage issues. If you have sandy soil, you can add peat moss to improve retention and lower pH.

  • 14 years ago

    Pine bark is pH neutral, fwiw. The wood + needles are where the acid action happen.

  • 14 years ago

    Jodi, you never mentioned the size of your plot. A few bales of spaghnum peat moss mixed in a 10'x10' plot will most definately drop your pH. I'm wondering what you added in the past to raise the pH and get the organic matter so high. That combination doesn't seem normal but a result of repeatedly dumping various products on a garden plot.

    Did the lab. do a N test or are they just recommending N? Most labs worth their salt don't bother with a N test in preplant season testing because it will leach out before you need it anyhow.

    I wouldn't do anything too drastic this year. Concentrate on getting another very carefully representative soil sample for next year and in the meantime check with neighbors to see if high pH is common in your area.

  • 14 years ago

    Soils in that part of the US are commonly high in pH.

    It's apple heaven, though.

  • 14 years ago

    I would add a substantial amount of peat moss.

    If you read some of the U. of M. bulletins, peat moss is most often referenced for long term acidification.

  • 14 years ago

    I bought a pin to test my soil PH. Some one mentioned I have to caliberate it how can I do that. Thamks

  • 14 years ago

    All organic acidification is temporary. You need sulfur to permanently sequester the calcium. To calibrate the test, a simple way is to get a pot of pure compost, with nothing added (my City adds some lime to its compost for example). I am fortunate enough that all my house plants soil is leaves, kitchen scraps, manure and wood chips, now fully decomposed. All pots record close to 6.5. Earthworm castings which have not been amended also will give you 6.5.

  • 14 years ago

    I calibrate with distilled water, myself. Clean the probe with it, dip and adjust the pH to 7.0. Check your paperwork with the device to see where/how to adjust to your preferred calibrating solution.

    It has to be freshly opened and rather newly produced distilled water if you use this method. Once you open distilled water it starts reacting with CO2 in the air and the pH can dramatically drop 1-2 points over the course of a few weeks because of the lack of a buffer.

  • 14 years ago

    bmoser, i read your post and realized i left out some very important information when i posted my question. i am feeling like an idiot right now as it may very well change some of the answers i have received. i have 7 raised beds, 4x4x12. i mixed together black dirt and compost that was purchased, by the truckload, from a local landscape supplier. this was all done this year. my intention was to grow veggies next to my house and water supply. the soil test was done by the univ of mn soil testing lab. they test for soil texture, organic matter, ph, phosphorus, and potassium, and then recommend appropriate N,P,K. one box has asparagus and two boxes have strawberries. the other four boxes have had a variety of veggies. i have been told that the high ph is likely decreasing my potential yield. i am disappointed in myself that i may have made an unwise choice in filling my beds and frustrated in not knowing how to fix it. i would really like to expand with more beds but only after doing some more research for soils. again, thanks for all the inputs, and sorry i left out that information. feeling like an idiot.....

    jodi

  • 14 years ago

    Jodi -- don't feel like an idiot. 'Cause if you're one, so am I!!

    I made a 48 square foot double dug raised bed this year (10 inches high) and added compost (mushroom & cow) and also bagged garden soil and dug it all into my native soil. I looked carefully at the ingredients of all the commercial gardening soils and chose one that had the most diverse set of ingredients. In my zeal to get everything dug in, it didn't dawn on me that one of the ingredients would raise my soil ph (ash). I had a soil test done by Clemson Extension Cooperative and lo-and-behold my ph was 7.4! I scratched my head and thought "how can this number be right" -- acidic soil where I live. LOL .... I already had my crops in so there wasn't anything I could do @ the time. Today I pulled out the remaining plants and double dug in 2.5 pounds of aluminum sulfate right before the rain hit. (This amount was recommended by my soil sample). All I have to do is turn my soil over every few days for 2 weeks & then I'm ready to plant my fall crops.

    Why don't you contact the MN Extension to find out exactly how much aluminum sulfate to add to quickly lower your ph into the desired range. I'm not familiar with your climate so I don't know if this would give you time to grow any fall crops. Good luck & stop beating yourself up!!

  • 14 years ago

    Thanks for providing very useful facts regarding soil.