تاثیر کاربرد هیومیک‌اسید غنی‎شده با نیتروژن (‏nha‏) بر ویژگی‎های مورفولوژیک و فیزیولوژیک ‏ذرت (سینگل کراس 704)‏

هیومیک‌اسیدهای غنی‎شده با نیتروژن (‏nha‏) به‎عنوان کود نیتروژن و محرک رشد گیاه مورد استفاده قرار گرفته‌اند. ‏در پژوهش‎‎‏ حاضر، ‏nha‏ از واکنش نیتریک‌اسید با هیومیک‌اسید (‏ha‏) استخراج‎شده از لئوناردیت تهیه شد و درصد نیتروژن ‏آن به‌روش آنالیز ‏chns‏ تعیین گردید. سپس، یک آزمایش گلخانه‎ای با کشت ذرت در قالب طرح کاملاً تصادفی با 16 تیمار ‏شامل شاهد (بدون مصرف اوره،ha‏ و ‏nha‏) و ‏اوره (‏u‏)، هیومیک‌اسید (‏ha‏)،اوره-هیومیک‌اسید (‏uha‏)، هیومیک‌‏اسید ‏غنی‌شده با نیتروژن (‏nha‏) و اوره-هیومیک‌اسید غنی‌شده با نیتروژن (‏unha‏) هر‌کدام در سه سطح و در سه تکرار انجام ‏شد. ‏سطوح تیمارها بر‌مبنای ربع (‏‎ mg n kg-1‎‏50)، نصف (‏‎ mg n kg-1‎‏100) و برابر نیاز کودی ذرت (‏‎ mg n kg-1‎‏200) ‏تعیین ‏شدند و در تیمارهای مخلوط، سهم برابری از نیتروژن برای اوره، ‏ha‏ و یا ‏nha‏ در نظر گرفته شد. نتایج حاکی از ‏کارایی مطلقاً زیادتر ‏nha‏ نسبت ‏ha‏ و نیز کارایی قدری زیادتر ‏unha‏ نسبت به اوره در ارتقای اغلب ویژگی‌های ‏مورفولوژیک ذرت بود. همچنین، به‎طور‌متوسط، شاخص کلروفیل برگ و غلظت‎های نیتروژن، نیترات و فعالیت آنزیم ‏نیترات‌ردوکتاز شاخساره در تیمارهایnha ‎‏ به‎ترتیب 11.5، 17.0، 35.2 و 29.4 درصد بیش‌تر از تیمارهایha ‎‏ بود. ‏با‌این‌حال، تیمارهای ‏unha‏ و اوره در اغلب صفات فیزیولوژیک نتایج تقریباً مشابهی را نشان دادند. بیش‌ترین غلظت ‏نیتروژن و نیترات در گیاه متعلق به ‏تیمار ‏u3‎‏ بود، اما بالاترین میزان آبشویی نیترات نیز در همین تیمار مشاهده شد که با ‏کاربرد تیمار ‏u3nha3‎‏ حدود 48.7 ‏درصد کاهش یافت. با توجه به یافته‎ها، ‏unha‏ می‎تواند به‌عنوان کود نیتروژن مطرح شود ‏که نیاز به پژوهش‌های بیش‌تری دارد.‏

effect of application of nitrogen-enriched humic acid (nha) on morphological ‎and physiological characteristics of maize (single cross 704) ‎

background and objectivesnitrogen (n) plays a major role in maize growth and yield. therefore, adequate supply of n is required ‎for successful maize production. however, application of chemical nitrogen fertilizers is associated with ‎some problems such as groundwater ‎pollution, nitrogen enrichment of surface waters, and nitrate ‎accumulation in agricultural products. ‎accordingly, nowadays a great attention has been paid to the ‎slow-release fertilizers. nitrogen-enriched humic acids ‎‎(nhas) are considered as promising slow-release ‎nitrogen fertilizers in agricultural systems. however, the ‎effects of these types of fertilizers on plant growth ‎and physiological characteristics have not been well ‎understood. for this purpose, the present study ‎investigates the effectiveness of nhas on the ‎morphological and physiological characteristics of maize as ‎well as nitrogen loss through leaching. ‎methodology ‎the nitrogen-enriched humic acids (nhas) were prepared through the simple process of nitration, and ‎from the reaction of nitric acid with humic acid (ha) ‎extracted from leonardite of yazd golsang kavir ‎company as an organic carbon source. then, a ‎greenhouse experiment in a completely randomized ‎design (crd) with three replications was conducted ‎to determine the effects of 16 treatments, including ‎control, urea (u1, u2 and u3), humic acid ‎‎(ha1, ha2 and ha3), nitrogen-enriched humic acid (nha1, ‎nha2 and nha3), urea-humic acid (u1ha1, u2ha2 ‎and u3ha3), and urea-nitrogen-enriched humic acid ‎‎(u1nha1, u2nha2 and u3nha3) on the morphological ‎and physiological characteristics of maize plant ‎‎(single cross-704). the levels of treatments were ‎determined as the quarter (50 mg n kg-1), half (100 mg ‎n kg-1) and equal (200 mg n kg-1) to the maize ‎fertilizer requirement. in the combined treatments of urea ‎and ha or nha, an equal fraction of the total ‎nitrogen was considered. after the end of the experiment, ‎using the standard methods, some ‎characteristics including root length, leaf area, plant height, root ‎volume, wet and dry weights of shoot ‎and root, leaf chlorophyll index, concentrations of phosphorus, ‎potassium, nitrogen and nitrate, and ‎nitrate reductase activity in both shoot and root were determined. ‎moreover, during the experiment and ‎on given days, the maize pots were leached and the obtained ‎leachate was collected for the nitrate ‎measurement. ‎findingsaccording to the results, the nitrogen content of the produced nha (3.3%) was about two times‏ ‏higher ‎than the ha (1.6%). in addition, the nha had higher‎‏ ‏carboxyl and phenolic hydroxyl content than the ‎ha. the ft-ir analysis showed the characteristic peaks of nitro (no2) groups at wavenumbers of 1541 ‎and 1336 cm-1 in the spectrum of nha. germination test indicated that the nha was not toxic to the maize ‎seeds. the results showed that the nha treatments had a much better influence on the plant ‎morphological characteristics than ‎the ‏ha treatments. this observation may be due to the negative effects ‎of ha application at high dosages. in comparision, the unha treatments were only slightly more efficient ‎than the urea treatments. combining‏ ‏nha with urea diminishes the adverse impacts of separate ‎application of these two fertilizers. on average, leaf chlorophyll index and concentrations of total ‎nitrogen, nitrate and nitrate reductase enzyme in shoot part of plants in the nha treatments were 11.5, ‎‎17.0, 35.2 and 29.4% higher than the ha tratments. the nitrate reductase concentration in the roots was ‎‎40.4% lower than the shoots. however, the unha and urea treatments showed almost similar efficiency ‎in improving physiological characteristics. the u3nha3 or u3 treatments, i.e. the highest level of ‎nitrogen, showed the highest efficiency which means the high nitrogen requirements of maize in pot ‎experiments. based on the results, the nitrogen supply to the maize plant increased the shoot ‎concentration of potassium higher than that of phosphorus. although the u3 treatment indicated ‎the ‎highest nitrogen and nitrate concentrations in both root and shoot, the highest nitrate leaching was ‎also ‎observed for this treatment. however, by using the u3nha3 treatment, the mean concentration of ‎nitrate ‎in the leachate decreased by about 48.7% as compared to the u3 treatment. ‎conclusion ‎findings of this research revealed that the combined fertilizer of unha can be ‎a good alternative for ‎urea. it could not only supply nitrogen for plants, but could improve plant vegetative ‎growth, and in turn ‎considerably reduce nitrate leaching, which has highly beneficial effects on nitrogen use ‎efficiency as well ‎as environmental issues.‎