EFFECT OF IRRIGATION INTERVALS AND NITROGEN FERTILIZER ON GROWTH AND YIELD OF TWO SWEET SORGHUM VARIETIES

Two field experiments were carried out at EL-Atf village, EL- Edwa, EL- Minia Governorate, Egypt during 2009 and 2010 seasons to study the effect of three irrigation intervals (irrigation every 10, 15 and 20 days) and four nitrogen fertilizer rates (without nitrogen added (control), 50, 70, and 90 kg N /feddan) on growth and yield of two sweet sorghum varieties (Honey and Rex).The experiments were laid out in split- split plot design with three replication.
               The obtained results showed that average values of leaf area index, stalk height, stalk fresh weight, sucrose percentage, stalk yield / fed and sugar yield ton /fed. were significantly affected by irrigation intervals in both seasons. Prolonging irrigation period from 10 to 20 days significantly reduced all above mentioned studied traits in both seasons.
                Results showed clearly that nitrogen fertilizer rates had a significant effect on all studied traits in both seasons. Increasing nitrogen fertilizer rates from 0 to 90 kg N/fed. significantly increased all studied characters, except sucrose % which decreased in both seasons.
               Results illustrated that sweet sorghum varieties significantly differed in all studied characters in both seasons, except sucrose which were insignificantly differed in both seasons. Sweet sorghum variety Honey surpassed variety Rex in all studied traits in both seasons.
               The interaction effect between irrigation intervals and nitrogen fertilizer rates was significant on all studied characters in both seasons. At all irrigation periods, increasing nitrogen fertilizer rate from 0 to 90 kg N/fed gradually increased all studied traits, except sucrose % which decreased in both seasons. The obtained results indicated that the interaction effect among irrigation intervals and sweet sorghum varieties was significant on all estimated traits in both seasons. On the other hand, sucrose % insignificantly affected in both seasons. At all irrigation intervals, sweet sorghum variety Honey exceeded variety Rex in all recorded traits in both seasons. The present results showed clearly that the interaction between nitrogen fertilizer rates and sweet sorghum varieties had a significant effect on all studied characters except on sucrose % which was insignificant in both seasons. The higher values of all measured characters were recorded when fertilized variety Honey with nitrogen fertilizer at the rate of 90 kg N/fed than variety Rex  at the same of nitrogen rate in both seasons. The recoded results showed that the interaction effect between irrigation intervals, nitrogen fertilizer rates and sweet sorghum varieties was significant on all studied traits, except sucrose % which was insignificant in both seasons. At the irrigation every 20 days, fertilized variety Honey with 90 kg N/fed gave the highest leaf area index, stalk height, stalk fresh weight, stalk yield/fed and sugar yield/fed. in both seasons.
                 Highly significant and positive correlation coefficients were detected between sugar yield and each of leaf area index, stalk height and stalk yield/fed.
              Generally, it could be recommended that under shortage of irrigation water, fertilized sweet sorghum variety Honey with nitrogen fertilizer at the rate of 90 kg N/fed. increased stalk and sugar yield ton/fed. under El-Minia Governorate conditions.