Effects of drought stress on biomass and carbohydrate contents of two sweet sorghum cultivars.

Sweet sorghum is adapted to the hot and dry climatic conditions. It can be used for different products such as food, feed, fiber and fuel. This study was carried out to evaluate the effects of four irrigation intervals and three harvesting dates on stem height, stem diameter, biomass, juice volume, brix, sucrose and invert sugar of two sweet sorghum cultivars. The results showed that delay in irrigation intervals from 7 to 21 day significantly decreased all the above characteristics expect for invert sugar which was increased. The highest biomass (56.50 t ha-1) and sucrose content (11.35 %) were obtained at 7 to 10 day irrigation interval. Both biomass and sucrose contents decreased significantly as harvesting date delayed from physiological maturity. Since both sweet sorghum cultivars, Keller and Sofra had similar biomass, sucrose content, brix and juice volume across irrigation intervals and harvesting dates, therefore it is suggested to plant either Keller or Sofra irrigated on 7 to 10 day interval and harvested at physiological maturity.

Effects of nitrogen treatments and harvesting stages on the aconitic acid, invert sugar and fiber in sweet sorghum cultivars.

Sweet sorghum is adapted to the hot and dry climatic conditions and its tolerance to slat is moderately. It can be used for different products such as food, feed, fiber and fuel. This study was carried out to evaluate the effects, three nitrogen treatments, and three harvesting stages on the aconitic acid, fiber and invert sugar of three sweet sorghum cultivars in the experimental station and the results showed that the effects were significant. Among nitrogen treatments, application of 100 kg ha-1 urea at planting and 200 kg ha-1 urea at 4 leaf stage had the highest aconitic acid (0.26%) and invert sugar (3.44%). Among sweet sorghum cultivars, IS2325 and Vespa had the highest aconitic acid (0.26%) and invert sugar (3.86%), respectively. Plant harvested at 4 leaf stage had the highest aconitic acid (0.26%) and the highest invert sugar (3.85%). Rio had higher fiber content than Vespa and IS2325 and all cultivars had the highest fiber content before chilling harvesting stage. In general, since high invert sugar and high aconitic acid interfere crystallization of sugar so, it is suggested that to plant Vespa, apply urea 100 kg ha-1 urea at planting, 100 kg ha-1 urea at 4 leaf stage and 100 kg ha-1 urea at booting and harvested before chilling that had lowest aconitic acid and invert sugar. Thereby, it is recommended to plant Vespa, apply urea 100 kg ha-1 urea at planting, 100 kg ha-1 urea at 4 leaf stage and 100 kg ha-1 urea at booting and harvested at 4 leaf stage that had the highest aconitic acid.

Inter-relationship between growth analysis and carbohydrate contents of sweet sorghum cultivars and lines.

The carbohydrate contents of sweet sorghum (Sorghum bicolor L. Moench) is an important industrial factor for crystal sugar or bioethanol production. In this study the relationship between growth analysis and carbohydrate contents were studied to recognize the best growth stages for sweet sorghum harvesting. Five sweet sorghum cultivars and four sweet sorghum lines were evaluated for leaf area index (LAI), net assimilation rate (NAR), relative growth rate (RGR) and stem crop growth rate (CGR) in relation to sucrose content, invert sugars and total sugar at booting, soft-dough, hard dough and post grain maturity Except at post grain maturitystage, the correlations among LAI, NAR and RGR forsucrose content and total sugar were positive and forinvert sugars were negative. The relationship between invert sugars including glucose, fructose, maltose and xylose athard dough stage regarding LAI, NAR and GRG were negative. As plant grows LAI, NAR and RGR increases which consequently increases sucroses content and decrease invert sugar.

Effects of irrigation water qualities on biomass and sugar contents of sugar beet and sweet sorghum cultivars.

An experiment involving four qualities of irrigation water two sugar beet and three sweet sorghum cultivars was conducted in a split plot design with four replications at Rudasht Drainage and Reclamation Experiment Station in 1999. The results showed salinity of water has an adverse effect on sugar beet and sweet sorghum biomass. Sweet sorghum cultivar SSV108 had the lowest biomass under all qualities of irrigation water Sweet sorghum cultivar Rio had the maximum biomass with water qualities of 2, 5, and 8 dS m(-1). Sugar beet cultivar 7233 had the maximum biomass with 11 dS m(-1). The effect of irrigation water quality was not significant for sugar characteristics such as brix, pol and purity. However, responses of cultivars on the above parameters were significant and sugar beet cultivars had higher brix, pol and purity and lower invert sugar and starch than sweet sorghum cultivars. In conclusion, sweet sorghum cultivars are not recommended to be irrigated with saline water of more than 8 dS m(-1) for sugar production. Under such condition, they may be suitable to be grown for forage purposes.

Effects of planting date and time of nitrogen application on yield and sugar content of sweet sorghum.

This experiment was conducted at Azad University experiment station to evaluate the effects of planting date and time of nitrogen application on yield and sugar content of sweet sorghum in 2003. Four planting dates (May 4, March 19, June 3 and June 18) and three stages of nitrogen application (3-5/8 leaf stage, boot stage and soft dough stage) were assigned to the main and subplots, respectively. Plant height and diameter, fresh stalk yield, total dry weight, brix value (soluble solids), sugar content and grain yield were affected by planting date. For all the characteristics, the maximum value was obtained by the first planting date. Only stem height, diameter and total plant dry weights were affected by time of nitrogen application. In these cases, nitrogen application at (3-5/8) leaf stage was superior to others. According to the results, sweet sorghum should be planted on the beginning of May and nitrogen be applied at (3-5/8) leaf stage.

Effect of water quality on yield of sugar beet and sweet sorghum.

To study the effects of quality of water on soil and plant, an experiment was conducted at Rudashat Drainage and Reclamation Experiment Station in 1999. Four irrigation water salinities (2, 5, 8 and 11 ds m(-1)) and two sugar crops (sugar beet and sweet sorghum) were used in this experiment. The results showed that under the same water quality, sweet sorghum used 2700 cubic meter per hectare less water than sugar beet. As the quality of irrigation water decreased, the soil salinity and exchangeable sodium percent increased which caused yield reduction for both plants. Sugar beet by accumulating Na and Cl in its leaves tolerated salinity but its usage as a forage crop caused some limitations, whereas sweet sorghum by not accumulating Na and Cl escape salinity and it can be used as a forage crop without any limitation.