Date of Award
Doctor of Philosophy
The sand-based rootzones of putting green require accurate soil tests and accurate interpretation of the results to properly develop a fertility program. The validity applying the BCSR theory of soil test interpretation has not been thoroughly evaluated for creeping bentgrass grown on low CEC sands. The objective of the first part of this research was to evaluate the BCSR theory for sand-based greens. Twenty-eight cation treatments of varying cation ratios were applied to 'Penncross' creeping bentgrass (Agrostis stolonifera L.) established on either calcareous or silica sand. There were no differences in quality or clipping yield. The bentgrass tolerated a wide range of applied cation ratios. The Ca:K ratios of silica sand ranged from 1:1 to 2:1, which according to the BCSR theory, they should be 13:1 and a Ca application would be recommended to correct the ratio. However, leaf Ca concentrations from grass grown on silica sand were high (12 g•kg -1) and leaf K concentrations were low (8.7 g•kg-1). It is recommended that the results of BCSR soil testing not be used as the final determining factor in developing fertility systems for sand-based golf course greens. Some soil testing procedures dissolve calcium carbonate (CaCO 3 which will cause an increase in the extractable calcium concentration and the estimated cation exchange capacity (ECEC). The second objective was to determine the affects of CaCO3 on different soil testing procedures and to make recommendations for soil testing methodology for sand-based putting greens. Raising the pH of the standard 0.5M ammonium acetate (NH4OAc) extracting solution from the standard pH 7.0 to pH 8.1 reduced the dissolution of CaCO3 measured by 33%. Measuring the CEC by the double extraction CaCl2/Mg(NO3)2 method produced CEC values that were 87% smaller than the ECEC calculated from NH4OAc pH 7.0. Of the methods evaluated for measuring exchangeable cations of calcareous sand samples, the NH4OAc at pH 8.1 offered results with the least amount of dissolution combined with the greatest ease of analysis. Cation exchange capacity determinations of calcareous sands should be done using a double extraction technique and should not be estimated by calculating an ECEC.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Rodney Alan St. John
St. John, Rodney Alan, "Soil testing methods and basic cation saturation ratios of creeping bentgrass greens " (2005). Retrospective Theses and Dissertations. 1773.