Agronomy Questions

Post your questions for the BFA Agronomy team to answer.

Submitted by TFabian on

What are the target numbers for the Saturated Paste Test?
When should the test be performed?
What do the results of the Saturated paste test tell you in regard to; soil conductivity, leaf tissue analysis, and soluble amandments?

Hi. I have really high phosphorous numbers, 500 ppm according to Mehlich lll. I read on your mineral descriptions that Zinc should be high if P is high. I also read that Zi should be 1/10th of P, which is consistent. However, what is the max levels of zi I should add per year? Is it more important to keep the P:Zi ratio 10:1 or to hav them misaligned but adhere to max levels? Thanks

Also, is there anything about the Mehlich III test that can be misleading about my P number?


Submitted by kclgarden on


According to a Mehlich III soil test done in June 2015, our garden here in Barnet, VT is low in Zinc. How and when would I apply Zinc? Would I broadcast Zinc sulfate? Dilute and spray? Can I apply this spring or would you recommend re-testing in the fall and applying before the winter?

In response to farmer_frank, according to Steve Solomon's worksheets, the max yearly application of Zi is 14ppa (10ppa if your soil is calcareous).


I am interested in trying Jerry Brunetti's chicken soup for the soil recipe as found in his latest book "Farm as Ecosystem." (which I gratefully recieved from the BFA). He suggests replacing sodium nitrate for the calcium nitrate but the calcium nitrate is in liquid form (2 gallons) while sodium nitrate is dry and must be put into solution. How much sodium nitrate by weight should be used for this recipe? Also there is a soluble soy based nitrogen on the market that is a 13-0-0. this seems like a nice option for nitrogen without the sodium and that is also sold in a powder. How much of that product could be used? And lastly, Jerry does give a basic recommendation regarding application rate for pasture but what would be a good rate to use this as a regular soil drench for vegetables? This recipe seems to have great potential as a less expensive DIY soil drench, but I just need some info. thanks. Dan

Submitted by farmershaun on


Damping off in the field? This happens to me mostly in the fall to my spinach, lettuce, turnips, beets and rutabagas. I cover the plants with row cover and when I come back to thin, sometimes half or all of my crop is gone. Is there something I can amend the soil with? I practice regenerative farming and am constantly adding nutrients to the soil.

Submitted by RPotwin on

Hi, How can I arrange a phone consultation session to interpret my Logan Lab soil report for my backyard garden?

Submitted by devima9 on

Hi, other than Spring Mix, what would be the best option(s) of how to generally mineralize our garden soils? we will be getting all soil tested, however would like to have some things on hand now.
am thinking about greensand and humates. thoughts?

Submitted by bfaagronomy on

Spring mix is a good one. Especially if you are in an area typically low in calcium. There is no one-size-fits-all recommendation, but using many different rock powders is a good way to spur microbial activity and diversity, and will also provide slow-release broad-spectrum minerals.

Greensand and humates are both good. Greensand is now in extremely short supply due to the closure of the only operating quarry in NJ. New sources are becoming available (slowly).

Also, everyone east of the rocky mountains who haven't been aggressively adding it for years are deficient in sulfur (please prove me wrong if you have a sample indicating you aren't), so elemental sulfur is a nearly universally necessary amendment (as is boron, granular calcium borate is my favorite source).

We did not get a soil test this year, but from our 2015 test we are low in calcium,potassium, phosphorus, zinc, boron, and manganese. we are also high in Magnesium. I know that amending in the fall is best practice, but since we were unable to do so this past fall, what can we do now, or in the spring to correct these issues for the up coming seasons?(we are located in south east Wisconsin going into our second season of growing on the property)

Submitted by bfaagronomy on

Best thing is to add what you're low in. And in the case of high Mg, you need to add even more Ca than normal to address that excess. Since you are low in Ca and high in Mg, Potassium is also critical, so add potassium. Potassium Sulfate is best. Depending on your calcium base saturation % you would want to use either gypsum or high-calcium limestone (or both) for calcium. All these things, and the trace elements, can be added any time of year (but if added when the ground is frozen, there is increased risk of early spring rains washing them away).

Submitted by bobcat230 on

What do you think is the max rate of manganese sulfate I can apply without harming my plants and microbes? Cobalt sulfate? Sodium molybdate? My ppm Mn is in the single digits and I would love to put down 100 lb/A elemental Mn to correct for a severe deficiency in my blueberries, but how much is too much? Depending on who I read, these values change. For example: In "Quantum Agriculture", Lovell says you shouldn't apply more than 25 lb/A/year manganese sulfate. On, citing , the max rate is 200 lb/A/year manganese sulfate. Significant difference. I'm having the same confusion with Co and Mo limits.

How do you account for amending 100 lb/A of sulfur deficiency on a soil that is receiving a substantial amount of sulfate from potash sulfate, manganese sulfate and gypsum? That is, can I apply the deficit as ag sulfur with the understanding that sulfates in these forms will not be readily available to my blackberries this year?

This same soil is very deficient in P, but perfect levels of Ca. What's the best OMRI certified option to amend for the P without using so much soft rock that excess Ca becomes a problem? Granted, I know we always need to promote the biology to make P available, but could there be an underlying cause of the deficiency? Perhaps the sulfur deficiency has something to do with it?

I just saw this... The max rate for GRANULAR manganese sulfate (~27%) is 200 lbs per acre. Granular is sometimes hard to find, so many recommendations list the max for powdered, water-soluble manganese sulfate, which would be MUCH lower, 25lbs per acre per year is probably about as high as I'd go for that.

For cobalt and molybdenum, see rates here:

Sulfates are readily available to plants (as sulfates are water soluble) and this is precisely why I always recommend elemental sulfur to fix a soil sulfur deficiency... sulfates leach too fast and don't address soil deficiency. Elemental sulfur takes 6 months to break down and offer many opportunities to become "attached" to the soil over that time. So if you have a sulfur deficiency in the soil, elemental sulfur is best. If you have an immediately sulfur deficiency in plants, sulfates will help more.

If you are very deficient in P, you'll likely have to add some to get the system working better (and deal with the extra Ca since I know of no organic P source that doesn't also have Ca). But the little bit of extra Ca will hurt you far less than a severe lack of P. As you know, work on your soil biology, so you may not have to add as much P as the test indicates, and definitely fix your S deficiency as adequate S is key to keeping the cations balanced (so the S will deal with any excess Ca).

I am looking at my soil report and my Al is quite high 574 ppm. What can I do about this in my raised beds for vegetables? Are there treatments I should avoid?
I am also quite low in Mn (15 ppm) and Boron (0.79 ppm) Are these connected in any way?

Despite what Logan Labs says about the desired Aluminum levels, I have actually never seen a soil test come back in their desired range (<200 ppm). 574 is actually right about the average for sample results I've seen, so I wouldn't worry. The best way to make sure Al isn't a problem is to move the soil toward balance.... if you're low in Ca, or Mg, or K, or S add them to get closer to the "ideal" level. I've certainly seen lower Mn and B levels, but you should address them. 20 lbs per acre of 10% granular Calcium Borate is my favorite Boron source, and 100 lbs per acre of granular Manganese Sulfate for the Mn deficiency (it'll take a few years of applications to bring it up to where you want it).

~ what is the composition of Spring Blend and of PlantSure and how do I know how much to apply?

~ do we have a call today 3/27? If so, what time?

~ since sulfhates are so soluble and don't contribute to the long-term soil balance improvement, should one apply both sulfhates and slower-release minerals at the same time - ie a quick shot in the arm plus long-term amendment?

Composition of spring blend:
Spring blend consists of (in 1,000 lbs, the recommended per-acre application rate):
150 lbs Humates, 100 alfalfa meal, 100 carbonatite, 100 ks plus, 100 tn rock phos, 100 sul-po-mag, 100 dynamin, 100 humus compost, 50 sea salt, 50 kelp, 50 zeolite.

Note that you should only apply Spring Blend if you need calcium... if you already have excessive calcium, either don't use it at all or use it at a much lower rate (250 lbs per acre or so).

The Agridynamics 'Plant Sure' product label info can be found here:

Sulfate forms of other elements do in fact contribute to mineral improvement... for instance Potassium Sulfate adds potassium, and Calcium Sulfate (gypsum) can add calcium. The thing that isn't improved by using sulfates is simply the sulfur levels (or at least not by much). For increasing the level of sulfur on a soil test, the only thing that has a big impact in the short term is elemental sulfur.

Submitted by Cindy on

I'd like to have a soil test done, but I need help with the Logan Test results. How can I get these interpreted with any amendments I need?

You can start by trying to do it yourself. You can listen to past lectures and S&N Conference talks to get some assistance, as well as reviewing our recommended targets for the minerals here:

If you want one-on-one assistance, it is available to members at a discount by contacting me here: agronomy @

Submitted by SharonS on

I attended Dan's 2-day workshop which was quite helpful. He had recommended The Ideal Soil by Michael Astera. That is also very good and helped me work through some of my remaining questions. If there is no workshop in your area some of the past workshops are up on the BFA site.

I have very small amounts to add to a 1000 sf plot: 4#Gypsum, 2# Biomin Copper (4% Cu), 11 oz Zinc (Zn) Sulfate, 7 oz Borax. Got any suggestions for how to distribute that evenly ;-)

Generally, for small plots like that, I'd recommend mixing the minerals with a carrier, like compost, as homogeneously as possible (sometimes I don't bother with the carrier, as sometimes that can create more problems). Then spread by hand (literally with your hands) out of a bucket. I find it's convenient to divide the space into equal size blocks (maybe 10, 100sq ft blocks), divide the material into that many buckets, and spread that way. When you do that, you have a very good, very apparent, visual cue if you are spreading at a rate that is too high or too low, and it allows you to tweak your technique so you get close to even coverage. If you're nervous, start by spreading at what you perceive as half, or even a quarter, of what you think the rate should be and adjust accordingly.

Looking at Claire's Logan soil test, she found base saturation of 80.64 Ca, 12.97% Mg, 1.77% K and and 0.82% Na. Exchange Capacity came in at 17.71 and pH at 7.6. Logan's table is not registering a ppa deficiency in magnesium, but my understanding is that 6:1 ratio of Ca:Mg is preferred and I'm not sure if that's by percent saturation or ppa, so I'm wondering what if anything needs to happen to adjust that critical Ca:Mg balance point. Sampling was done in December so I'm wondering also if that might have lowered the potassium levels. Sulfur was low at 24ppm.

Submitted by RPotwin on

Hi David,
I need some clarification regarding advice given during the consult call for my 16'x16' vegetable garden
Question #1: You had recommended 1/2 lb of elemental sulfur this year and 1/4 lb for the next 2 years. I bought Espoma Soil Acidifier which is 30% sulfur (a mixture of elemental sulfur and gypsum). Should I adjust the application amount?
Question #2: The copper sulfate (Bonide) which I bought, is in powder form. Your recommended application for a granular form was 1 ounce. Can I apply the powder all at once? Thanks!

Hello David,

Couple of questions about Azomite and Cobalt sulfate purity.

1. Azomite. It looks like a pretty good bang for your buck for micronutrients.

What are your thoughts on it? I see in the analysis that it has 11% Al2O3 or Alumina. Is that going to raise the Aluminum concentration too much? or will the Alumina leach out of the soil after a year or so?

Also will the 1.8% Calcium have a noticeable effect and possibly throw off the Ca, Mg base saturation ratio? So is it safe to use at the recommended rate by the manufacturer?

2. Cobalt Sulfate. I looked up buying Cobalt Sulfate from pottery supply online but the only stuff I can find for a reasonable price is around 99% purity. My soil test for my farm from Kinsey Ag calls for 8g/1000 sqft of 27% or something Cobalt Sulfate.

So my question here is how do I extrapolate their math on 27% to 99% without overdoing it? And what is a safe application rate for home garden use/1000 sqft with the 99%?

Thank you


Also, What organic matter percentage that shows up a soil test would support biological life in the soil the most? Do I want to see 5% or 6% etc.? And what is the best way to incorporate more organic matter without throwing off the cation ratios on a big area? Is it just cover cropping? or sending Kinsey a sample of the manure compost from my local beef farmer etc etc. We just don't generate a lot of compost nor do we have the time to tend it.

Thank you

Submitted by Greg Walsh on

Hi David! 2 questions...

1. Question on Sodiun Moldybate. I calculate it is 43.75% Mo. Looking at your yearly limit Applications (below), it seems to suggest a 5% concentration. This leads to a 10 lb/acre allowable limit. Where did I go wrong?

2. I saw in another post that elemental sulfur is the only way to raise a low Su test. I had been relying on gypsum. Should I not count the Su in gypsum and just go for elemental Su to raise the levels. THANKS



Molybdenum: 0.5 lb/acre actual, up 0.25 ppm/yr

Sodium Molybdate (5%) 3.5 oz/ 1,000 sq ft, 10 lbs per acre