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| I just received the results from my first ever soil tests, and I'd really appreciate some feedback on the numbers. It looks like phosphorus (and to a lesser extent potassium in area #1) is my major limiting factor. The lab that I used (UMass) doesn't make micronutrient recommendations, so I'm especially interested in thoughts/suggestions about those (many of which appear to be quite low and/or out of balance). * * * Test #1 - New Vegetable Garden (1 year) Soil pH: 6.7 Based on these results, the lab recommended no lime and 2-3 lbs of 10-10-10 (or 3-4 bushels of well-rotted manure and 3.5 lbs of bone meal or 10 lbs of rock phosphate) per 100 sq ft. * * * Test #2 - Established Vegetable Garden (10+ years) Soil pH: 6.5 Based on these results, the lab recommended no lime and 3-4 lbs of 5-10-5 (or 1/4 lb of nitrogen and phosphorus from organic sources) per 100 sq ft
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Follow-Up Postings:
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- Posted by TheMasterGardener1 5B (My Page) on Fri, Feb 22, 13 at 13:53
| I would go with what they recommended. Otherwise, you have some very good soil there! In your garden bed it is a 9% OM- thats really good! |
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| It looks like your organic matter and PH are good. The phosphorus sounds low to me and the calcium in the new garden is higher in saturation than ideal. |
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| Not much you can do about the Ca. P should be above 30. The rest is fine. You can choose to intervene in any number of ways. Superphosphate is great, but chicken manure is even better for this specific purpose and is free on craigslist. To estimate how much you are adding, you need about 20 ppm. Soil down to one foot is approximately one ton for 12 sqft. If you have 120 sqft of beds, you need a little less than 1/2 lb of P. |
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| That's a near-ideal soil report for NC. Your pH ranges and nutrient values are great except for P. You P levels are a in the low/mid-range as noted by another poster above. Given your CEC of 17, you have a lot of room for addition without it becoming toxic or limiting. though. Given the clay content of our soils in NC, it's going to hold onto a lot of whatever you add. Getting it near 30ppm would be great, but even if it goes to 100ppm it's doubtful it would be toxic or limiting. You can shoot for over-application without worry of it leeching out. A high OM soil will leech P faster, but our soils in NC contain a lot of clay in the root zone even if there's a lot of OM in the first few inches of soil. That said, I would shoot for a slight over-application rather than a huge over-application. Getting it close to 30ppm should be the goal, not 100pm (or 50ppm). I'm just saying you have some room for error on over-application thanks to your CEC + our high clay content soils. You probably won't have to lime your soils for another 2-3 years unless you happen to live really close to a bunch of chicken/hog farms, non-paved roadways that kick up dust, or power plants. Also, for future reference, soil tests are free in NC and paid for by taxes/fees on fertilizer sales. http://www.ncagr.gov/agronomi/uyrst.htm |
This post was edited by nc-crn on Fri, Feb 22, 13 at 18:33
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| Thanks for the input everyone. I was pleased with the results -- I really didn't know what to expect, and it's good to know that my soil is in pretty good shape overall. I'll definitely address the phosphorus shortage in the next few weeks. Is the consensus that I don't need to worry too much about the micronutrient numbers? Many of them appear to be lower than is ideal (or so my limited research has suggested). For what it's worth, I usually add about 1 lb/100 sq ft of kelp meal annually and rely primarily on Alfalfa pellets for nitrogen, both of which should be adding a variety of micronutrients and other beneficial compounds. Would anything else be warranted? You pretty much summed up my soil, nc-crn. The subsoil is clay, clay, and more clay. I once did one of those soil and water in a mason jar experiments, and the the water was cloudy for days. I never did see a sand or silt layer. As for the free NC soil tests, that's the primary reason that I've never gotten around to testing my soil previously. Since it was free, it seemed silly to pay for an out of state lab test, but, since it required a 30 minute drive to the county extension office for a sample container, I never got around to it. Finally, I decided to just pay for a report and be done with it. |
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| If your soil has no sand or silt, only clay, you will not see a sand or silt layer. That jar test is valuable only for the amount of organic matter, the topmost layer, although it can give you an indication of what minerals are in your soil. If you do not see any sand or silt the what you have is clay. In some 50 years of doing that simple soil test I have seldom seen a good loam soil, most of the tests show either sand or clay. The recommended dosages of "fertilizer" are minimal amounts that most likely are really not needed. It looks to me that you have done good and have close to a good healthy soil. Keep in mind that too much Nitrogen causes lush green growth that is more attractive to insect pests. |
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| I am a bit surprised that the established garden has the same Cu, Zn and B as the new one. Presumably, it has been manured often right? |
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| Zn/B/Cu are held tightly by the high clay soils found in NC. At lower pH it cleaves off some of them (especially Zn + Cu). At a normal-higher pH it's all held well. |
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| I've never added manure of any kind, so I assume nc-crn's reply would be the right one. Can anyone comment on the iron level? My soil appears to be low in available iron, and it's my understanding that the iron oxide that colors my red clay subsoil is largely insoluble. At the same time, I've never noticed any symptoms of iron deficiency. Also, if I were to use an organic amendment for boosting the potassium level in the new garden (3-4 oz of actual K per 100 sq ft), would K-Mag/Langbeinite be a reasonable choice (applied at a rate of 1 lb or so per 100 sq ft), or would I be better off going with Sulfate of Potash (at half the rate above) since the Mg level is already quite good. I'm thinking that the extra Mg in the K-Mag wouldn't be a big deal, but I don't want to overdo anything at this point. |
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| in clay soils a high magnesium level compared to the calcium level can tighten the soil and make it stickier and cloddier. That would hurt less in sandy soils...might help even. |
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| Let me rephrase my question: how much organic matter has the old garden received over the years? Clay may hold these minerals, but if there is more of it, the same fraction of a larger quantity will be available. In my current garden, with more than one foot of organic matter added, P and K are above optimal (100 and 300 ppm IIRC. Sorry, Michigan doesnot test for Fe/B/Cu/Zn)). In the surrounding soil, P is no more than 5-10 ppm, and K around 100ppm. Surely OM will increase all micronutrients. |
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| Sorry, glib. I have a tendency to hear things (and respond) very literally. It drives my wife crazy. The older garden has received more organic matter (an initial addition of several inches of municipal compost and a thick annual mulch of chopped tree leaves) and more soil amendments (seed meals, alfalfa, kelp, and rock phosphate), so it is interesting that the numbers are identical for boron, zinc, and copper. That being said, what I characterized as the "new" garden was formerly a strawberry bed, and it did receive a couple of inches of peat moss and compost when it was established, lighter mulching with tree leaves, and occasional light applications of some of the soil amendments that I mentioned above. My ballpark guess would be that the OM and soil amendment ratio would be something like 3:1 for the old vs new gardens. |
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