@article { author = {Siadat, SeyedAtaollah and Derakhshan, Abolfazl}, title = {Construction of Critical Nitrogen Dilution Curve Based on Stem Dry Matter in Rapeseed}, journal = {Plant Productions}, volume = {45}, number = {1}, pages = {143-156}, year = {2022}, publisher = {Shahid Chamran University of Ahvaz}, issn = {2588-543X}, eissn = {2588-5979}, doi = {10.22055/ppd.2020.31971.1854}, abstract = {IntroductionThere are mathematical equations to distinguish nitrogen (N) status based on the concept of critical nitrogen (Nc), the lowest N concentration required to achieve maximum growth. The Nc demonstrates the ideal N status in crops. Whenever crop N concentration is greater than the Nc, at that time N is in surplus, but if it is less, then N is inadequate. The contribution of the stem dry matter (SDM) toward total crop dry matter is significantly higher than that of other tissues, therefore, it is the most determinant factor for N dilution of the whole plant. The objectives of this research were to construct a Nc dilution curve based on SDM and to evaluate the plausibility of this curve for assessment of the N nutrition status of spring rapeseed. Materials and MethodsA field experiment was conducted with seven levels of N fertilizer application (0, 50, 100, 150, 200, 250 and 300 kg N ha-1) in which the amount of the SDM and stem N concentration (SNC) of two spring rapeseed cultivars (Hyola 401 and Dalgan) were measured during the growing season. The approach proposed by Justes et al. (1994) was used to construct the SDM basis Nc dilution curve. The N nutrition index (NNI) on each sampling date was calculated by dividing actual SNC by stem Nc concentration. The accumulated N deficit (Nand) in rapeseed stems for each sampling date was determined by subtracting the N accumulation in stems under the Nc condition from actual N accumulation in stems under different N fertilizer application rates. Results and DiscussionOverall, both SDM and SNC showed an increasing and decreasing trend with increasing crop age, respectively, regardless of fertilizer treatment. The Nc dilution curve of both cultivars during the growing season was described by the equation Nc = 5.71SDM-0.29. Both NNI and Nand criteria were able to diagnosis the N deficiency or excess in the spring rapeseed cultivars studied. At all of the crop growth stages, there was a significant positive correlation between the difference value of the N application rate (∆N) and the difference value of NNI (∆NNI). For both cultivars studied, however, the positive correlation between ΔN and differences in Nand among N fertilizer treatments (ΔNand) was not significant at early growth stages. In any case, for accurate management of N fertilizer during the growing season, it is sufficient to determine only one of the two NNI or Nand criteria per day from planting to silique formation, and then the N fertilizer required for maximum growth is calculated based on the equations presented to describe the relationships between ΔN and ΔNNI or between ΔN and ΔNand. The most important application of the Nc dilution curve is to determine the N requirement of crops during the growing season under variable field conditions. These curves can be used as ideal and economically efficient tools for accurate management of fertilizer in the field, which is very important from the aspect of environmental protection and human health. Both NNI and Nand were well able to distinguish the N status of spring rapeseed. ConclusionThe present Nc dilution curve based on SDM provides an insight into N nutrition status in spring rapeseed crop and can serve as a novel tool to improve N fertilization management in spring rapeseed. }, keywords = {Nitrogen deficiency,Nitrogen nutrition index,Nitrogen use optimization,Precise nitrogen management}, title_fa = {ساخت منحنی رقیق شدن نیتروژن بحرانی در کلزا بر پایه ماده خشک ساقه}, abstract_fa = {مصرف بی‌رویه کود نیتروژن نگرانی‌ها در مورد سلامت انسان و پایداری محیط‌زیست را افزایش داده است. مدل‌های ریاضی توصیف‌کننده رقیق شدن نیتروژن در بافت‌های گیاهی در طول دوره رشد را می‌توان برای برآورد وضعیت تغذیه و نیاز نیتروژنی گیاه در طی فصل استفاده کرد. این مطالعه در سال زراعی 96-1395 با هدف ساخت منحنی رقیق شدن نیتروژن بحرانی (Nc؛ حداقل غلظت نیتروژن لازم برای رشد حداکثر) بر پایه ماده خشک ساقه در کلزای بهاره در دانشگاه علوم کشاورزی و منابع طبیعی خوزستان انجام شد. آزمایش مزرعه‌ای با هفت سطح مصرف صفر، 50، 100، 150، 200، 250 و 300 کیلوگرم نیتروژن خالص در هکتار انجام گرفت و ماده خشک و غلظت نیتروژن ساقه دو رقم کلزای بهاره (هایولا 401 و دلگان) در طی فصل رشد اندازه‌گیری شد. رقیق شدن نیتروژن بحرانی هر دو رقم در طی فصل رشد توسط یک منحنی با معادله Nc=5.71SDM-0.29 توصیف شد. شاخص تغذیه نیتروژنی (NNI) و کمبود نیتروژن تجمعی (Nand) به‌خوبی قادر به تشخیص کمبود یا بیش‌بود غلظت نیتروژن در گیاه بودند. در همه مراحل رشدی گیاه، همبستگی مثبت و بسیار معنی‌داری بین تفاوت مصرف نیتروژن (∆N) و تفاوت NNI میان تیمارهای کودی (∆NNI) وجود داشت. بااین‌حال، همبستگی مثبت بین ∆N و تفاوت Nand میان تیمارهای کودی (∆Nand) در مراحل ابتدایی رشد معنی‌دار نبود. به‌هرحال، برای مدیریت دقیق نیتروژن در طی فصل تنها کافی است یکی از دو معیار NNI یا Nand در هر روز از کاشت تا تشکیل خورجین‌ها تعیین شود و نیتروژن مورد نیاز برای دستیابی به حداکثر رشد بر اساس معادله‌های ارائه‌شده جهت توصیف روابط بین ∆N و ∆NNI یا ∆N و ∆Nand محاسبه گردد.}, keywords_fa = {بهینه‌سازی مصرف نیتروژن,شاخص تغذیه نیتروژنی,کمبود نیتروژن,مدیریت دقیق نیتروژن}, url = {https://plantproduction.scu.ac.ir/article_15837.html}, eprint = {https://plantproduction.scu.ac.ir/article_15837_598b5b1268ce1fbe9b044f3202cabc6a.pdf} }