Doctor of Philosophy (PhD)
Plant, Environmental Management and Soil Sciences
Optimizing flowering in the LSU AgCenterâ€™s Sugarcane ( Sacchrum spp. hybrids) Breeding Program is an important step in the variety development program. The effect of nitrogen and ambient air temperature in pot cultured sugarcane were examined as a means of improving sugarcane flowering. The experiment was conducted on agronomic and reproductive traits of sugarcane at the Sugar Research Station, St. Gabriel, LA, on sugarcane genotypes subjected to artificial photoperiod regimes. The potting media consisted of equal parts of washed sand, Canadian peat moss, and a Commerce silt loam soil (fine-silty, mixed, nonacid, thermic aeric Fluvaquents). Early nitrogen (22.4-22.4-22.4 kg ha-1) in addition to a high nitrogen potting media (>200 mg kg-1) was necessary for adequate vegetative growth and stalk numbers for tasseling. Leaf macronutrient levels were examined at reproductive growth stages as affected by pre-photoperiod nitrogen fertilizers (22.4-22.4-22.4 kg ha-1 and 0-22.4-22.4 kg ha-1). Since tasseling in nitrogen and no-nitrogen treatments were 77% and 25%, respectively, the critical leaf nutrient level for nitrogen at the vegetative stage for sugarcane intended for tasseling should be 12.4 g kg-1. A chlorophyll meter was used to collect chlorophyll readings from the same leaves that were sampled for plant analysis. The initiation stage was the only stage that both leaf nitrogen (r = -0.34) and chlorophyll meter readings (r = 0.80) showed significant associations. A chlorophyll index level (34.53) was developed as a maximum threshold level for sugarcane breeding genotypes at the initiation stage. Average daily maximum temperature for specific time intervals can affect sugarcane tasseling. A reduced regression model (P=0.02) for the overall tasseling regime indicated that the percent tasseling is expected to increase 4.19 percent when the May 30 â€“ June 14 temperatures increase by one degree above 31.9Â° C, decrease by 4.36 percent when the June 15- June 30 temperatures increase by one degree above 32.1Â° C, and decrease by 4.69 percent when the August 16 â€“ September 10 temperatures increase by one degree above 33.1Â° C. These results help to explain the variation in tasseling percentages that have been encountered over the years when above average temperatures were experienced.
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LaBorde, Christopher Michael, "Sugarcane tasseling under artificial photoperiod conditions as affected by nitrogen rate and temperature" (2007). LSU Doctoral Dissertations. 2970.