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River Valley District

Soil Management

Crop production depends heavily on having nutrients readily available for plant uptake. Management of all nutrient sources, including commercial fertilizer, compost and manure, within the constraints of farm production systems and operational goals are prerequisite for both profitable crop production and environmental sustainability.

Inappropriate management of these sources can lead to a reduced economic return and environmental degradation of both, surface and ground water. It is imperative that nutrient management planning activities are recognized and carried out.

Soil Testing


 Salt Index



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Soil pH

The following analogy (adapted from University of Nebraska, Bulletin G74-153) may give a simple explanation. Consider two-coffee pots (figure A) one 50-cup capacity and one 10 cup, both having the same size indicator tube and spigot. Coffee in the indicator tube represents the active acidity (measured by regular pH) and that coffee in the pot represents the reserve acidity (measured by buffer pH). Let the large pot represent a clay soil high in organic matter while the small pot represents a sandy soil. Both pots have equal amounts of coffee in the indicator tube; i.e., same active hydrogen, so same soil pH.

Now open the spigot and remove one-cup of coffee from each pot (figure B). Removing one cup of coffee from each pot could be equated to the addition of small amount of limestone to an acid soil. Opening the spigot will cause the level of coffee in the indicator tube to drop below the level in the pot, but will return to almost the original level (clay soil) when the spigot is closed. The momentary drop of coffee in the indicator tube represents the initial increased in pH when lime is added (affects active hydrogen), but reserve hydrogen (similar to coffee in the pot) soon equalizes the effect from the lime and the pH returns to essentially its original level (clay soil, figure C). Thus, if the pH is 6.5 or lower, a buffer pH is run to measure the reserve acidity. The result of the buffer pH shows the amount of lime required to neutralize a major portion of the reserve acidity. The relative amounts of coffee in the two pots (figure C) show why a sandy soil and clay soil with the same pH result in different lime requirements. For example, the small addition of limestone (equivalent to removing one cup of coffee from each pot) reduced the total coffee (reserve acidity) by 10% in the small pot (sandy soil), but only 2% of the large pot (clay soil). In a similar manner, 1 ton of agricultural limestone will make a greater difference in the pH of a sandy soil than of a clay soil.

Soil Acidity

 Soil pH