Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Plants, Soils, and Climate


James P. Thorne


With increasing pressure on economical production of crops, more fertilizers are being applied to the soil each year to increase crop yields. Economical production of crops with applications of fertilizer requires an evaluation of the essential elements of the various crops so applications of fertilizer will not exceed the law of diminishing returns.

Because varying soil, moisture, and climatic conditions influence the response to added fertilizers, some workers (18, 26, 38) have contended that the only reliable way of determining the fertilization needs of a crop is to conduct a trial on the particular farm. The length of time involved to determine the fertilizer requirements of a crop, along with the fact that climatic conditions change, limits the value of this method. With observation type trials, yield increases are easily over-looked and the expense involved in conducting a properly designed trial is beyond the scope of the farmers.