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Thesis (M.S.)—University of Nebraska—Lincoln, 1972. Department of Agronomy


Copyright 1972, the author. Used by permission.


The sandhill transition area of Nebraska represents a vast potential reservoir for food and fiber production. The soils of this area are lower in natural fertility than many of the finer-textured soils of the state. Properties of these soils are vastly different from others having a history of intense cultivation. In addition many of these soils are being developed for irrigation. The question becomes what kinds and quantities of fertilizers are required to bring these soils into profitable crop production. These soils test among the lowest in the state in exchangeable magnesium and potassium. However, will these soils support the intense demands of crops such as irrigated corn or pasture, including bromegrass and orchardgrass? If potassium fertilizer is used on these soils will the natural soil magnesium level be adequate for high yields?

With the recent increased interest in irrigated pastures, new demands are being placed on these coarse-textured soils. Feeding forage produced on these soils may introduce a new consideration in the proper fertilizer program. A condition in ruminants known as “grass tetany” has been correlated with low magnesium content of forage. Conceivably this may be a concern if irrigated pastures are grown on these relatively low magnesium soils. If the depression of magnesium uptake in crops occurs in this soil, potassium fertilizer recommendations may need to be tempered accordingly.

With these question becoming more pressing, the potassium-magnesium study was undertaken with the following objectives.

  1. Determine the influence of soil potassium saturation on growth and magnesium uptake by corn.

  2. Determine to what degree magnesium uptake is influenced by potassium saturation in terms of concentration and dry matter production.

  3. Determine the likelihood of reducing magnesium levels with potassium fertilizer applications to levels associated with grass tetany.

  4. Determine the influence of various potassium and magnesium levels in the soil on the uptake of other nutrients.

  5. Determine the feasibility of studying the above objectives in a field experiment on the soil studied in the greenhouse.

Advisor: Delno Knudsen