Soil Test Results (Veggie Garden)

10 years ago

Interesting results from my veggie garden. I started it 3 years ago from a sorry patch of clay. Soil test at that time said that P & K were both low, & pH was 6.0. Interesting that the Phosphorus went so high so quickly. Raised bed built up with peat moss & store-bought compost (year 1), and subsequent compost since then.

I'm in Middle TN, about 25 miles northwest of Nashville, zone 6b.

Anyway... without further delay:

Water pH 7.3
Phosphorus 312 (Very High) (these are in lbs per acre)
Potassium (High)
Calcium 5377 (Sufficient)
Magnesium 415 (Sufficient)
Zinc (Sufficient)
Copper 0 (Sufficient)
Iron 8 (Sufficient)
Manganese 50 (Sufficient)
Boron 3.4
Sodium 12

I'm curious to hear opinions of folks smarter than me re: the P, K, and other minerals. Thoughts?

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Comments (6)

User
10 years ago
Lower the pH (not vital, but could help) to at least 6.5 if you feel like it...7.3 isn't bad or too limiting for most crops, especially in TN. A lot of winter crops prefer a lower pH, but 7.3 isn't going to make them unable to grow. Potatoes and eggplant are about the only crops that would very much like to see the pH lowered.

Fertilize with N sources, which should be cheaper, avoiding the NPK fertilizers. You don't need to adjust your P or K...it's hard to do and mostly unneccesary when other nutrients are well represented. It's rarely toxic...it mostly just goes unused by plants.
Kimmsr
10 years ago
What is the level of organic matter in that soil? I would be less concerned about that pH if the soil humus levels was in the 6 to 8 percent range. While the ideal soil pH range is 6.2 to 6.8 that 7.3 is not that far out of range and as this from Colorado State University might be of some help understanding nutrient availability.

Here is a link that might be useful: nutrient availability

This post was edited by kimmsr on Thu, Aug 29, 13 at 6:54
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Your basic problem was going to A&M for a soil test instead of The Texas Plant and Soil Lab. For $35 you will get all your testing, the testing you didn't want to pay for, and more. Best of all they don't destroy the organic matter with hydrochloric acid to do the test, so they can tell you with a lot more accuracy what nutrition is AVAILABLE to your plants. For your iron/zinc deficiency, find some greensand and apply at 40 pounds per 1,000 square feet. You won't find greensand at your big box stores. Give it three full weeks to works its magic and you will be back where you want to be. Ironite doesn't seem to have any effect in our soil. Living Earth Technology makes some excellent products. I won't buy anything else. They tried to enter the San Antonio compost market on an industrial scale but the competition down here is pretty firmly entrenched. I can get their bagged material at Lowe's. Potassium, calcium, magnesium, and sodium need to be in proper proportion to each other. The Texas Plant and Soil Lab would have explained that to you. They would make their recommendation based on the ratio of one to the others, not the 'total amount allowed by law.' Kelp and blood meal are not the only sources of fertilizer. Many of us use ground up grains (corn, soy, alfalfa, flax, cottonseed, etc.) to feed the soil microbes. Here is a link that might be useful: Texas Plant and Soil Lab
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Mels Mix is all organic matter, except for the vermiculite for drainage, but it would help to know how much OM is in the gardens soil. That both places tested pretty much the same indicates a problem with the test, not the results. You need a good reliable soil test done. You cannot determine what or how much "fertilizer" to put down based on the information you have.
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Nitrogen availability depends on soil temperature whihc governs the activity of the Soil Food Web, which is why most soil test labs no longer test for N. Most often when someone has a soil test done by a good soil tesing lab the recommendations come back to apply 2 pounds of Nitrogen per 1,000 square feet, which if you think about that is a pretty minimal amount. I have found the soil test kits sold from the garden centers to be very unreliable. In comparing two different manufacturers kits I got widely divergent results. If the water in your home was acidic enough to have any affect on your soil you would not be able to drink it. If you have finished compost available now spread it on your soil now and let the Soil Food Web slowly work it into the soil.
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I'm a doofus. I missed the fact that the analysis was conducted on your 2/3 soil to 1/3 mushroom compost blend. Anyway, my comment about 0.0 ppm available nitrogen stands. I think it's a lab error. My comments about salinity also stand because we don't know the starting salinity of the compost or the soil. That being said, the final blend is 23% O.M. by dry weight, which is super high. If the mushroom compost was 1/3 of the final blend by volume, that would put you in the 7 to 8% organic range by dry weight if mixed with a mineral soil. And that's if the compost itself were high in organic material. (The analyses I looked at for the compost ranged from about 30 to 60% O.M. by dry weight). So, it would be a safe bet that your 4-way soil is probably around 15% O.M. by dry weight or a little higher. That means that it was probably about 50% to 60% organic material by volume and who the heck knows what that O.M. was. If it was raw wood chips, you would still have some available nitrogen in the analysis, but potentially not enough to balance carbon and it's feasible that you do indeed have a nitrogen draw issue. Or, if it has a heavy manure component, that could contribute to salts. (even a high quality greenwaste compost will often have a salinity level of 5 to 7 dS/m). Also consider that such a high amount of organic matter has the potential to hold too much water, especially if drainage isn't all that great at the bottom of the planters.
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TXEB
10 years ago
Overall, looks pretty decent. The pH can be brought down over time, but if your soil organic matter is high I wouldn't be concerned about it at all. I would, however, avoid adding anything with significant P to that soil. Manures and composts made with manures can be surprisingly significant sources of P. For an alkaline calcerous soil your approaching the levels where you can begin to see problems from excess P (much over 300 lbs/acre or 150 ppm). Keep the P out and let it moderate for a couple of years, and it should be great.

Article linked below form the Aggies about too much P.

Here is a link that might be useful: Aggies - Excess Phposphorus

This post was edited by TXEB on Thu, Aug 29, 13 at 13:34
User
10 years ago
In TN the pH will probably drop naturally over time unless the garden is located near a gravel road (or some other source) dumping liming material into the garden. The natural water sources, rain water, and air particulates (which effects the rain water quality) tends to lean toward more acidic water sources.

I wouldn't be too concerned about a pH of 7.3 unless you wanted to crop potatoes as a veggie. Eggplant likes it a bit lower, too, but it's not as picky.
wayne_5 zone 6a Central Indiana
10 years ago
Is there any other reason for low ph for potatoes than for scab reasons?
User
10 years ago
Nope, it's pretty much just scab/disease reasons. Though potatoes do prefer a lower-than-neutral growing pH (much like eggplants), the main reason is scab avoidance. You won't get a failed or very limited crop just because your pH is 7-7.5.

There are scab-resistant varieties out there (like Burbank russets) for higher pH soils.

This post was edited by nc-crn on Thu, Aug 29, 13 at 19:58

Soil Test Results (Veggie Garden)

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wayne_5 zone 6a Central Indiana

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