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 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).