تاثیر مدیریت توزیع نیتروژن بر جذب و کارایی مصرف نور در ژنوتیپ های سورگوم علوفه ای sorghum bicolor l. moench))

یکی از مهمترین عوامل موثر بر اختلاف عملکرد در ژنوتیپ های سورگوم علوفه ای (sorghum bicolor l. moench) چگونگی دریافت و جذب تشعشع فعال فتوسنتزی تحت تاثیر میزان و چگونگی توزیع نیتروژن مصرفی می باشد. به منظور ارزیابی تشعشع فعال فتوسنتزی تجمعی (cpar) و کارایی مصرف نور(rue) در شرایط تقسیط و عدم تقسیط کود نیتروژن، طرح آماری به صورت کرت های خرد شده در قالب بلوک های کامل تصادفی و در سه تکرار بر روی 15 ژنوتیپ سورگوم علوفه ای (لاین های امید بخش) به اجرا درآمد. در طول آزمایش، صفات شاخص سطح برگ، عملکرد ماده خشک و میزان تشعشع فعال فتوسنتزی جذب شده طی پنج مرحله نمونه برداری اندازه گیری و محاسبه شد. نتایج تجزیه واریانس نشان داد اثر ژنوتیپ بر عملکرد ماده خشک گیاه و کارایی مصرف نور معنی دار (p≤0.05) بود و حداکثر و حداقل آن به ترتیب 17/20 و 56/13 تن در هکتار برای ماده خشک و 18/4 و 06/3 گرم بر مگاژول برای کارایی مصرف نور به ترتیب به ژنوتیپ های kfs17 و kfs10 اختصاص داشت. شیوه توزیع نیتروژن و اثر متقابل نیتروژن و ژنوتیپ بر شاخص سطح برگ معنی دار (p≤0.05) بود و توزیع دوباره نیتروژن موجب افزایش شاخص سطح برگ به میزان نه درصد و همچنین par تجمعی به میزان دو درصد شد. نتایج این بررسی حاکی است که اختلاف در عملکرد ماده خشک ژنوتیپهای سورگوم علوفه ای ناشی از اختلاف درهر دو جزء موثر در تولید ماده خشک یعنی کارایی مصرف نور و par تجمعی بود.

The Influence of Distribution Nitrogen Fertilizer Management on Absorbed and Radiation Use Efficiency in Forage Sorghum (Sorghum bicolor L. Moench)

IntroductionDry matter production is a function of photosynthesis active radiation absorption (APAR) and radiation use efficiency. Sorghum genotypes are different in total dry matter, but the reason of these different is not clear. Producing dry matter is affected by nitrogen distributing method, but the way of this effectiveness on producing of dry matter in sorghum genotypes is not also specified. This paper focused on evaluation of receiving and absorbing PAR, which is affected by nitrogen usage method in forage sorghum genotypes, and reasons of the differences between these genotypes in production of dry matter. The variation in efficiency of APAR depends on two chemical and morphological characteristics of the vegetation, including canopy nitrogen content (NCANOPY) and the canopy average for mass per unit of area (Merea).Material and MethodsIn order to investigate the cumulative photosynthetically active radiation (CPAR) and radiation use efficiency (RUE) under distributing of nitrogen side dressing and nondistributing conditions, an experiment was conducted at Khorasan Razavei Agriculture and Natural Resources , Research Center Mashhad , Iran. The statical method was according to spilt plots base on randomized complete block design with three replicates. The main plots were fifteen forage sorghum genotypes (Promising lines kfs1, kfs2, kfs3, kfs6, kfs7, kfs8, kfs9, kfs10, kfs11, kfs12, kfs13, kfs15, kfs16, kfs17, kfs18) and the subplots consisted of distributing of nitrogen side dressing and nondistributing. The samples were obtained 5 times during the growing season for determination of some characteristics including dry matter (TDM), leaf area index (LAI) and Photosynthetically active radiation (PAR). Then total dry matter (TDM), cumulative Photosynthetically active radiation (CPAR) and radiation use efficiency (RUE) were calculated by these traits. Absorbed radiation measured by Sub Scan model SSIUM1.05 on five location of each plot on bottom and top of each plot at 12 o’clock each day, five times by destructive samples. Radiation use efficiency (RUE) calculated by regression lines obtained by slope of total dry matter (TDM) and cumulative radiation use absorption (CPAR) by this equation Y=a0*x.Results and DiscussionThe results showed that the effect of genotype on total dry matter was significant (p <0/05). The maximum and minimum were 20.17 t/ha and 13.56 t/ha belonged to genotypes (14) and (8), respectively. The nitrogen fertilizer distributing method and interaction of nitrogen and genotype on leaf area index were significant (p <0/05). Nitrogen distribution caused leaf area index and photosynthetically active radiation (PAR) to grow up to %9 and %2, respectively. The genotypes had significant effect on radiation use efficiency. The maximum and minimum RUE observed as 4.18 g/mJ2and 3.06 g/mJ2 these were related to genotypes 14 and 8, respectively.ConclusionSplitting nitrogen fertilization in forage sorghum genotypes caused increasing of total dry matter, while absorbed PAR increased cumulatively. A comparison between methods of nitrogen usage showed that a little change in increasing radiation use efficiency occurred by changing the nitrogen splitting method, versus non splitting condition in sorghum genotypes. The results illustrated, these two components (e.g. cumulative photosynthetically active radiation and radiation use efficiency) are affected by nitrogen fertilization distributing method in forage sorghum genotypes, as well as nitrogen distribution effect on increscent of cumulative PAR, leaf area index and radiation use efficiency. Results of this study showed that the differences of total dry matter in sorghum genotypes is due to both two parameters of cumulative photo synthetically active radiation and radiation use efficiency.