Our Logan Labs Target Values & Yearly Limits

My desired CA:MG, based on TEC

68:12 - 8.5-20
67:13 - 8
66:14 - 7.5
65:15 - 7
64:16 - 6.5
63:17 - 6
62:18 - 5.75
61:19 - 5.5
60:20 - 5.35 or less

Target levels of macro minerals

Sulfur: 75 ppm
Phosphorus: 75 ppm
Calcium: 60-70%
Magnesium: 12-18%
Potassium: 3-5%
Sodium: 1-3%

Target levels of trace elements

Boron: 3 ppm
Iron: 2x Mn
Manganese: 80-90 ppm
Copper: 4 ppm
Zinc: 8 ppm
Cobalt: 2 ppm
Molybdenum: 1 ppm
Selenium: 0.5 ppm
Aluminum < 200 ppm

Application limits (Pounds per acre)

Gypsum: 2000 lbs
Sulfur (Elemental, granular, 90%): 100 lbs. Up to 200 lbs in high TEC soils with extreme cation excesses.
Boron: 2 lbs (actual)
Fe: 400 lbs (Iron Sulfate 24%)
Mn: 200 lbs (Manganese Sulfate 28%)
Cu: 35 lbs (Copper Sulfate 23%) [note: 10 lbs of 23% raises by 0.6 ppm]
Zn: 35 lbs (Zinc Sulfate 36%)

Cobalt: 4 lbs per acre of material (27% Co), up 0.54 ppm/year
Molybdenum: 0.5 lb/acre actual, up 0.25 ppm/yr
Selenium: 0.25 lb/acre actual, up 0.125 ppm/yr

Cobalt Sulfate (27%) 1.5 oz/ 1,000 sq ft, 4 lbs per acre
Sodium Molybdate (5%) 3.5 oz/ 1,000 sq ft, 10 lbs per acre
Sodium Selenate (6%) 1.5 oz/ 1,000 sq ft, 4 lbs per acre

Guidelines for Saturated Paste Test

pH: 6.2
Sulfur: 5 ppm
Phosphorus: 0.4 ppm
Calcium: 25-30 ppm/60%
Magnesium: 5-6 ppm/20%
Potassium: 12-15 ppm/15%
Sodium: <4-5 ppm
Boron: 0.08 ppm
Manganese: 0.10 < 0.25 ppm
Copper: 0.07 ppm
Zinc: 0.10 ppm

Sodium molybdate multiplier given above is incorrect according to my information. It simply can't be 5% as molybdenum is quite a heavy element. Without looking up the formula and adding it up, an online search suggests that 39.5% is the correct figure.

Submitted by bfaagronomy on

As I always say, you have to check the specific product you buy. I have found both 5% and the 39.5% you are referring to, and most of the materials we helped people find to date was, in fact, 5%. You are right to point out that if it is pure Sodium Molybdate, then it should be around 39.5%... but what happens all the time in this industry is that something that is called Sodium Molybdate can, and often is, "cut" with, or diluted with, something else. A binder perhaps, sometimes just something "inert" like clay or even sand (in the case of some selenium products I've seen. This is sometimes done by the manufacturer to help people avoid using so much that it is toxic.

So again, I will reiterate to everyone... the numbers above should ALWAYS be checked against the specific products you are using, and you should generally follow the application instructions for the specific product.

Submitted by bfrick on

Thank you for this info! Super helpful in interpreting the results of my first LL soil test. I noticed you didn't mention Sodium (except in context of saturated paste test), or Silicon targets. Do you have targets for those?

Thanks for informative info and detail instruction. It's really useful for me. Gmail recently changed their web design. Some of those updates appear to be most useful for businesses, with others designed for consumers.