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Soil and Plant Potassium as Affected by Soil Temperature Under Controlled Environment¹

ABSTRACT

Studies on the effect of soil temperature and moisture on the K-supplying power of two soils were carried out in a growth chamber. Air temperature and lighting were programmed to follow a constant daily cycle, while soil temperature was kept constant with an insulated water bath assembly. Soil and plant K determinations were made at each of five stages of growth. Regression and correlation analyses were performed to describe the various response curves. Correlations were also made to describe the relationships between the plant and soil K measurements.

Results obtained from these studies showed soil temperature to have a tremendous effect on the K-supplying power of a Floyd soil and much less of an effect on a Milaca soil. Plant yields were increased similarly on both soils with increased soil temperature, but K yields on the Floyd soil were increased from two to three times those of the Milaca soil. A significant response to applied K was obtained on both soils at low soil temperatures, but only the Milaca soil showed a substantial response at the high soil temperature. Correlations between plant and soil K measurements indicated that plants on the Milaca soil utilized exchangeable K at both low and high soil temperatures, whereas those on the Floyd soil utilized exchangeable K at low soil temperatures, and both exchangeable and nonexchangeable forms at high soil temperatures. Both soils fixed substantial amounts of applied K, but temperature effects on the two soils were very different and it appeared as though different fixation processes were involved. It was concluded from these studies that the erratic response to K fertilization on the Floyd soil in different years can be attributed primarily to differences in soil temperatures. Yield increases from K applications were obtained on this soil at low temperatures but not at high temperatures.

¹ Paper No. 5325 Scientific Journal Series, Minnesota Agr. Exp. Sta., University of Minnesota, St. Paul. Contribution from the Soils Department described here was in part supported by a grant from the American Potash Institute and represents a portion of the dissertation presented by the first author to the Graduate School in partial fulfillment of the requirement for the Ph.D. degree.

² Assistant Professor of Crop Science, North Carolina State of the University of North Carolina at Raleigh, and Professor of Soils, University of Minnesota.

Received for publication March 5, 1964. Accepted for publication May 25, 1964.