اثر اسید هیومیک بر فراهمی کود فسفر و برخی صفات فیزیولوژیکی گیاه کلزا

فسفر در مقایسه با دیگر مواد مغذی ضروری، دارای تحرک و قابلیت دسترسی کمتر برای گیاهان است. اگر چه فسفر به اشکال آلی و غیر آلی در خاک‌ها فراوان است، اما اغلب عامل مهم یا حتی محدود کننده اصلی برای رشد گیاه است. در این پژوهش اثرات مصرف هم زمان اسید هیومیک و کود فسفر و روش های کاربرد آن بر صفات فیزیولوژیک و فراهمی فسفر در گیاه کلزا (رقم هایولا 50) مورد بررسی قرار گرفت، بدین منظور آزمایشی به صورت فاکتوریل در قالب طرح کاملاً تصادفی در 3 تکرار به صورت گلدانی به اجرا درآمد. تیمارهای شامل فسفر در سه سطح (0، 50 و 100 میلی‌گرم کود سوپرفسفات تریپل بر کیلوگرم خاک)، اسید هیومیک در سه سطح (0، 0.5 و 1 گرم بر کیلوگرم خاک) و روش های کاربرد همزمان اسید هیومیک و فسفر بود. اثرات متقابل اسید هیومیک و فسفر و روش های کاربرد آن بر تمام صفات اندازه گیری شده در سطح یک درصد معنی دار شد. نتایج اثرات متقابل سه جانبه سطوح اسید هیومیک، سطوح فسفر و روش‌های کاربرد نشان داد که بیشترین مقادیر در انواع کلروفیل (a، b و ab) و کارتنوئید در تیمار کودی 100 میلی گرم بر کیلوگرم فسفر و سطح 1 گرم بر کیلوگرم مصرف همراه با آب آبیاری اسید هیومیک به دست آمد. بیشترین مقدار غلظت فسفر اندام هوایی با میانگین 0.30 درصد در تیمار یک گرم بر کیلوگرم اسید هیومیک همراه با آب آبیاری با سطح 100 میلی گرم بر کیلوگرم فسفر مشاهده شد هر چند با تیمار 0.5 گرم بر کیلوگرم اسید هیومیک همراه با آب آبیاری از لحاظ آماری اختلاف نداشت. بیشترین مقدار فسفر عصاره گیری شده به روش اولسن با میانگین 41.16 میلی گرم بر کیلوگرم و روش سلطان پور و شواب با میانگین 5.24 میلی گرم بر کیلوگرم مربوط به تیمار 100 میلی گرم برکیلوگرم فسفر و مصرف خاکی یک گرم بر کیلوگرم اسید هیومیک بود. همچنین همبستگی بالا و معنی داری بین فسفر عصاره گیری شده به روش اولسن و سلطان پور و شواب با صفات مورد مطالعه مشاهده شد. به نظر می رسد که استفاده از فسفر همراه با اسید هیومیک، بیشتر از کاربرد فسفر به‌تنهایی، می تواند باعث افزایش فسفر قابل دسترس در خاک و نیز غلظت فسفر در گیاه کلزا (هایولا 50) شود.

The Effect of Humic Acid on the Availability of Phosphorus Fertilizer and some Physiological Traits of Rapeseed (Canola)

Introduction: One of the most important needs in the farm planning is the evaluation of different systems of plant nutrition. By supplying the correct way of plant nutrition, one can preserve the environment and increase the efficiency of agricultural inputs. Humic acid contains many nutrients that increase soil fertility, soil organic matter content, and access to macro and micronutrients by preventing the formation of insoluble salts and chelating properties. Phosphorus and humic acid stimulate vegetative growth, improve reproductive growth, and increase the quantitative and qualitative yield of plants. In this regard, the positive effects depend on the amount and how they are applied. The present study was conducted with the aim of investigating the effects of different levels of humic acid and phosphorus fertilizer on phosphorus availability and photosynthetic pigments (a, b and carotenoids) in canola (cv. Hyola 50).;Methods and Materials: The soil used in this study was collected from 030 cm layer of a soil profile passed through a 2mm sieve after airdrying. The soil chemical and physical properties were then determined. The pot experiment was conducted as factorial based on completely randomized design with three replications. Treatments include phosphorous fertilizer as super phosphate in three levels (0, 50 and 100 mg/kg) and humic acid in three levels (0. 0.5 and 1 gr/kg soil), phosphorous and humic acid application ways. Humic acid and phosphorous treatments were mixed in various forms including simultaneous mixing of humic acid and phosphorous fertilizer in the soil matrix, application of humic acid and phosphorous via irrigation water and coting of phosphorous fertilizer via solid humic acid before soil application. Then 10 canola seeds were planted in each pot at 2cm depth which were declined to 4 plants in each pot after emerging and greening phases. At the end of the growth period (158 days), the plants were harvested. Determination of phosphorus concentrations of plant extracts by molybdenum vanadate or yellow method and chlorophyll content (a, b and ab) and carotenoids were measured precisely before harvesting using Barnes method. After harvesting the plants, the soil was immediately airdried and passed through a 2mm sieve. Then, the amount of phosphorus was determined by sodiumDTPA and sodium bicarbonate. The statistical results of the data were analyzed using SAS software and LSD test (at 5% level) was used for comparing the mean values.;Results and Discussion: The interactions of humic acid and phosphorus and its application methods were significant for all measured traits at the 5% level. The results of the triple effects of humic acid levels and its application at the presence of phosphorus treatments showed that the highest chlorophyll (a, b and ab) and carotenoid content was obtained at 100 mg/kg phosphorus and 1 g/kg humic acid along with irrigation water. The highest concentration of plant shoot phosphorus with an average of 0.30% was observed in 1 g/kg humic acid with irrigation water at the level of 100 mg/kg phosphorus, although had no significant difference with 0.5 g/kg of humic acid with irrigation water. Maximum amount of P was extracted by Olsen method with the mean of 16.14 mg/kg and Soltanpour and Schwab method with the mean of 5.24 mg/kg obtained in 100 mg/kg phosphorus and 1 g/kg soil humic acid application. There was a significant correlation between the phosphorus extracted by Olsen method and Soltanpour and Schwab method (r = 0.95), which was significantly correlated with concentration of phosphorus (r = 0.84) and (r = 0.85) (P lt;0.05). There was also a significant correlation between fresh and dry aboveground biomass, types of chlorophyll (a, b and ab) and carotenoids with phosphorus extracted by Olsen and Soltanpour and Schwab methods at 5% significance level.;Conclusion: P adsorption capacity is a function of many factors. Application of phosphorous fertilizers in calcareous soils, due to the presence of calcium with high activity, results in the formation of calcium phosphates, which becomes insoluble, over time. Humic material in interaction with phosphorus in the soil can reduce phosphorus stabilization and increase plant available phosphorus. The results of this study showed that the use of phosphorus with humic acid, rather than the use of phosphorus alone, could increase the available phosphorus in the soil and also the phosphorus concentration within the plant.