Soil Amendments
Dr. Dave Franzen
Extension Soil Specialist,
North Dakota State University
Several categories of materials:
Soil conditioners
Fertilizers not sold for fertilizer value.
Biological activators
Biological inoculants
Organic materials
Materials with hormonal activity
Low analysis fertilizers
In order to be registered in North Dakota, the material needs to be true to guaranteed analysis, or show that it does something positive to soil or crop.
Lately, marketers have registered unsupported products by adding a small amount of fertilizer and turning into the ND Dept. of Ag. only that part of the label showing the guaranteed analysis. After registration, the marketers advertise the “amazing” properties of the product.
Only a few soil conditioners have been shown to have any effects on soils in North Dakota. Leonardite actually
degrades soil conditions in most studies, or has no effect. Volcanic ash ties up P. Other soil conditioners studied have shown no effect or soil effects only, and not crop enhancements.
Calcium sulfate - CaSO4. 2H2O – Gypsum There are many “Possible” uses for gypsum in an agricultural system.
Possible Uses-
-Counteracts sodicity
-Better soil aggregate stability
-Prevents crusting
-Decreases pH of sodic soils
-Increases acidity of acid soils
-Source of sulfur
Sodium soils are nasty beasts.
Residual extractable sodium
Treatment Depth Tile spacing meq/100
0 6” 30 ft. 5.13
10 6” 30 ft. 5.83
10 6” no tile 5.38
10 2 ft. 30 ft. 5.75
27 3 ft. 30 ft. 1.74
Check ---- ------- 6.09
Average, tillage to 3 ft. only - 5.43
Average, 27 t/a gypsum + tillage – 2.04
Do not confuse a sodic soil with a saline soil. Our saline soils are nearly always high in gypsum. More gypsum will not get rid of gypsum!!
One study has shown that on really low organic matter soils, 25 tons/acre of gypsum may decrease bulk density.
(Rothamstad Annual Rpt, 1971.) However, the practicality of this is highly debatable.
Studies in Europe have also shown that high rates of lime (~50 ton/acre) also decrease bulk density or make them easier to cultivate.
Gypsum is not a “snake-oil”, but it can play snake-oil on TV.
Gypsum should not be used to decrease salinity.
Gypsum should not be used to modify most pH levels.
Gypsum might have some value on certain sodium “enriched” soils.
Gypsum is great for peanuts.
Biological activators/inoculants- Many contain bacteria Azotobacter or Clostridium
Only fix 1-2 lb/a N per year. Food sources are nearly always the limiting factor.
P inoculation?
Not a true inoculation. No intimate relationship with plant. Acidifies its environment, and may release about 10 lb P2O5 in calcareous soils. Acid soils has no effect on P release or plant uptake.
Organics?
Fish extracts, byproducts from seafood industry. Seaweed extracts. Other byproducts. Amounts of plant food not high enough to make any difference in plant yield.
Hormones or materials that have hormonal activity?
Plants already make gibberillins, auxins, cytokinens. These hormones are made and destroyed in the plant
continuously to regulate plant growth. Do we really know when the plant will benefit?
Cerone is a wheat growth hormone. Why don’t you use it???? We don’t know how the year will shake out and it can make the wheat really short.
Low rate fertilizers- Slow-release N. High purity phosphate starters.
Low rate P fertilizers- Studies across the Midwest, including ND, shows that high priced, high purity fertilizers perform no better and are often more harmful to the seed than 10-34-0 based starters.
Dr. Goos and I are probably going to retire close together. This is a retirement venture we have been considering-
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