اثرات برگ‌‌پاشی اسید هومیک و عصاره سیر بر جذب عناصر غذایی (npk) و رشد گندم در شرایط تنش خشکی

با رویکرد توجه به محیط‌زیست، استفاده از مواد طبیعی می‌تواند در کاهش اثرات مخرب کودهای شیمیایی و تنظیم‌کننده‌های رشد مصنوعی تاثیر‌گذار باشد. در این تحقیق اثر برگ‌‌پاشی اسید هومیک و عصاره سیر بر وزن خشک و جذب عناصر نیتروژن، فسفر و پتاسیم در گیاه گندم در شرایط تنش خشکی بررسی شد. این آزمایش در سال 1398 در قالب طرح کاملاً تصادفی با آرایش فاکتوریل در سه تکرار در شرایط گلخانه‌ای انجام شد. خاک موردمطالعه با کلاس بافتی لوم، دارای ph 8.11 و  ec 1.28 دسی زیمنس بر متر بود. فاکتورهای آزمایشی شامل تنش خشکی در سه سطح 95، 65 و 45 درصد ظرفیت زراعی، کاربرد عصاره سیر به‌صورت برگ‌‌پاشی در سه سطح صفر، 2 و 4 درصد و اسید هومیک به‌صورت برگ‌‌پاشی در دو سطح صفر و 300 میلی‌گرم بر لیتر بود. نتایج نشان داد که کاربرد برگی اسید هومیک و عصاره سیر هر یک به‌تنهایی، اثر مثبتی بر پارامترهای وزن خشک و جذب نیتروژن و فسفر داشت. علاوه ‌‌بر این عصاره سیر جذب پتاسیم گیاه را نیز افزایش داد. ازآنجایی‌که تنش خشکی تمام صفات موردبررسی را کاهش داد، برگ‌‌پاشی با عصاره سیر در شرایط تنش خشکی توانست بر جذب نیتروژن، فسفر و پتاسیم تاثیر‌گذار باشد که این اثر در تنش‌‌های کم بیشتر بود به‌طوری‌که در تنش خشکی 65 درصد ظرفیت زراعی، جذب نیتروژن با کاربرد عصاره سیر 2 درصد و جذب فسفر و پتاسیم با کاربرد عصاره سیر 4 درصد عملکرد بهتری نسبت به سایر سطوح عصاره سیر داشت؛ بنابراین به نظر می‌‌رسد که برگ‌‌پاشی با عصاره سیر و اسید هومیک به‌عنوان مواد طبیعی محرک رشد گیاه توانست تاثیر مطلوبی بر رشد و جذب عناصر غذایی گیاه بگذارد که تاثیر عصاره سیر در مقایسه با اسید هومیک بیشتر بود و در شرایط تنش خشکی نیز عصاره سیر تا حدودی توانست اثرات منفی تنش را کاهش دهد.

the effects of foliar application of humic acid and garlic extract on nutrients uptake (npk) and growth of wheat under drought stress conditions

introductionwith the approach of attention to the environment, the use of natural materials can be effective in reducing the harmful effects of chemical fertilizers and artificial growth regulators. drought stress is one of the main limitations of food production around the world, and due to increasing population and water deficiency, there is a global attention for using some materials to increase resistant of plant to drought stress. chemical stimulants are currently used for decreasing negative effects of water stress in plant. now a days, use of natural materials, such as plant extract is recommended by researchers. garlic extract is one of the natural extracts that contains many enzymes and more than 200 biochemical compounds that, due to its richness in minerals and plant hormones, causes cell enlargement, cell division and, plant growth. humic acid is created from the decomposition of organic matter and is beneficial to plant growth and development. therefore, the aims of this research were to study the effects of using natural substances of humic acid and garlic extract on nutrients uptake (npk) and growth of wheat plant under drought stress.materials and methodsthis study was performed during 2018 in a completely randomized design with factorial arrangement in three replications under greenhouse conditions. the studied soil with texture class of loam had ph = 8.11 and ec = 1.28 ds m-1. experimental factors include drought stress at three levels of 95%, 65% and 45% of field capacity, garlic extract at three levels of foliar application of 0, 2% and 4% and humic acid at two levels of foliar application of 0 and 300 mg l-1. drought stress were treated by the weight method, 17 days after sowing. foliar application of humic acid (twice, 13 and 20 days after threating the drought stress) and garlic extract (three times, 18, 24 and 27 days after threating the drought stress) were performed by spraying 150 ml pot-1 of the solutions in each time. the plants were harvested 54 days after sowing and the parameters of shoot dry weight and uptake of nitrogen, phosphorus and potassium in plant were measured. statistical analysis was done using sas 9.4 software and the comparison of means was done using tukey’s test at the 5% probability level.results and discussionthe results showed that foliar application of humic acid and garlic extract alone had a positive effect on dry weight and uptake of nitrogen and phosphorus of shoot. in addition, garlic extract also increased the potassium uptake. drought stress reduced all investigated parameters; however, foliar application of garlic extract under drought stress conditions increased the absorption of nitrogen, phosphorus, and potassium. in 65% of field capacity, nitrogen uptake by using 2% garlic extract and phosphorus and potassium uptake by using 4% garlic extract had a maximum amount compared to others. in general, garlic extract, due to its antioxidant properties and the presence of growth-promoting compounds such as minerals, vitamins, phytohormones, sulfur compounds, enzymes and amino acids, can improve growth parameters and absorption of nutrients in wheat plant. humic acid improved growth parameters due to its role in increasing cell membrane permeability, respiration and photosynthesis, phosphate absorption, root and cell expansion, and acting as hormone-like substances.conclusionthe foliar application of wheat plant with garlic extract and humic acid as natural stimulants had a favorable effect on the plant growth and nutrients uptake. garlic extract was more effective than humic acid in reducing the negative effects of drought stress. finally, the use of natural materials such as garlic extract and some high consumption compounds such as humic acid can be an environment-friendly and safe approach to improve plant growth and to reduce the destructive effects of chemical fertilizers and synthetic growth regulators.