Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Release patterns of N (NO(,3)-N+NH(,4)-N and NH(,4)-N), P, K, Mg and Ca were determined over a 124-day period in 1980 using six rates of a sulfur-coated slow-release fertilizer, three micronutrient mixes, and two application methods. Leachate extractions from 3.75 liter containers of Gardenia jasminoides 'Radicans' were taken biweekly for laboratory nutrient analyses. Media samplings were collected at monthly intervals. Leachate analyses showed the 17.82 kg/m('3) rate produced significantly higher NO(,3)-N+NH(,4)-N, NH(,4)-N, and K levels at all eight extraction intervals. Levels of P showed wide variations without trend. Media samplings showed the 17.82 kg/m('3) rate produced higher NO(,3)-N, P, and K levels. Higher media pH levels were produced by the 2.97 kg/m('3) rate. No clearly defined trend was evidenced in the media Ca and Mg data. Release of leachate NO(,3)-N+NH(,4)-N, NH(,4)-N, and K showed a significantly higher effective nutrient level for approximately 30 days longer for the top dressed method compared to the incorporated method of application. Method of application exerted very little consistent effect on the levels of P in leachates. Media sampling results were generally the same as leachate results for NO(,3)-N, P, and K. Media levels of Ca and Mg were generally significantly higher when the SulfurKote was incorporated. Top dressing showed a consistent decrease in pH throughout the study, while incorporation showed a consistent increase during the same period. Neither of the three micronutrient mixes differed significantly in their influence on leachate NO(,3)-N+NH(,4)-N, NH(,4)-N, and K. Micromax resulted in higher P levels at three testing dates. For media samplings Pro-Start produced significantly higher NO(,3)-N and Ca levels, Micromax resulted in higher P levels, while ProGrow produced higher Mg levels at day-33 and day-60. Micronutrient mixes did not exert a clearly defined effect on media K or pH levels. Release patterns of N (NO(,3)-N+NH(,4)-N and NH(,4)-N), P, K, Mg and Ca were determined in 1981 over a 156-day period comparing five different commercially available formulations of sulfur-coated fertilizers. Nutrient analyses were obtained from leachate extractions and media samplings. Leachate extrations and media samplings generally showed the same conclusions. Release of NO(,3)-N+NH(,4)-N in leachate extractions showed a significantly higher effective nutrient level for approximately 70 days longer with Scotts SREF compared to Sta-Green 13-13-13, Sta-Green 24-4-10, LESCO 20-6-12, and LESCO 14-14-14. Sta-Green 13-13-13 produced significantly higher levels of P 100 days longer than the other four treatments. Sta-Green 13-13-13 or Scotts SREF produced significantly lower pH readings compared to the other three treatments. Plant quality ratings substantiated these results.