نوع مقاله : مقالات پژوهشی
نویسندگان
دانشگاه ارومیه
چکیده
فرآیندهای فیزیولوژیکی و زیستی متعدد در گیاه، تشکیل کربوهیدرات ها و پروتئین، فعال سازی حدود 50 آنزیم برای نقل و انتقال انرژی همچنین کاهش هدررفت آب از منافذ برگ، تحت تأثیر حضور پتاسیم در گیاه است (16). عملیات باغداری طولانی مدت ممکن است بعضی تغییراتی را در ویژگی های جذبی و توزیع شکل های پتاسیم ایجاد کند. برای بررسی این فرضیه، خاک های سطحی 5 زیرگروه از 15 سری خاک باغی و بکر هم جوار در جنوب دشت ارومیه که برای مدت بیش از 5 دهه تحت عملیات باغداری طولانی مدت قرار گرفته اند تشریح و نمونه برداری شدند. نمونه های خاک پس از هوا خشک شدن و عبور از الک 2 میلی متری تحت آزمایش های مختلف فیزیکوشیمیایی قرار گرفته و شکل های مختلف پتاسیم و هم دماهای جذب پتاسیم تعیین شدند. نتایج نشان داد که در بیشتر خاک های مطالعه شده عملیات باغداری طولانی مدت به تبعیت از تیپ های مختلف خاک، فعالیت های باغی و خصوصیات خاک باعث کاهش پتاسیم محلول از 05/0 تا 48/1 میلی مول در لیتر، پتاسیم تبادلی از 01/12 تا 98/285 میلی گرم بر کیلوگرم خاک، پتاسیم قابل استفاده از 42/10 میلی گرم بر کیلوگرم خاک تا 65/180 میلی گرم بر کیلوگرم خاک، پتاسیم غیرتبادلی از 05/43 تا 65/114 میلی گرم بر کیلوگرم خاک، نسبت جذب پتاسیم از 08/0 میلی مول بر لیتر تا 17/1 میلی مول بر لیتر، درصد پتاسیم تبادلی از 49/0 درصد تا 47/3 درصد شده است. در این بین پتاسیم محلول و پتاسیم غیر تبادلی به ترتیب بیشترین و کمترین کاهش را در بین شکل های پتاسیم نشان داد. مطالعات هم دماهای جذب نشان داد که جذب پتاسیم در سری خاک های بکر نسبت به خاک های باغی بیشتر بوده و در زیرگروه ورتیک اندوآکوئپت (سری قوت تپه) جذب پتاسیم حداکثر بوده است.
کلیدواژه‌ها
عنوان مقاله [English]
Effects of Long-term and Continius Horticatural Practices on Distribution of Potassium Forms and their Adsorption Properties in Urmia Region
نویسندگان [English]
- zahra amirpour
- salar rezapour
- behnam dovlati
University of Urmia
چکیده [English]
Introduction: Multiple biological and physiological processes in the plant, including carbohydrates and proteins formation, activation of 50 enzymes for energy transmission as well as reducing water losses from leaf pores, are mostly affected by the presence of potassium in the plant. In order to test this hypothesis, five soil subgroups (TypicCalcixerepts, FluventicHaploxerepts, TypicEndoaquepts, TypicHalaquepts and VerticEndoaquepts) belonging 15 series of gardened and adjoining virgin soils were described and sampled. The studied soils had been influenced under horticultural practices for over five decades.
Materials and Methods: The soil samples were analyzed for different K forms, K adsorption and physico- chemical properties after air drying and grinding to pass through a 2 mm-sieve. The particle-size distribution was determined by the hydrometer method (Bouyoucos, 1962). The total carbonate in the soil expressed as the calcium carbonate equivalent (CCE) was determined by a rapid titration method (Nelson, 1982). Organic matter (OM) was measuredby the Walkley and Black (1934) dichromate oxidation method. The pH of the soil was analyzed in 2:1 CaCl2/soil suspension using glass electrode pH meter (Crockford and Norwell, 1956) and EC was detected in a saturated extract. The cation exchange capacity (CEC) was measured using sodium acetate (1 M NaOAc) at pH 8.2 (Chapman, 1965). Water soluble K was extracted with deionized water (1: 5 w/v) after shaking for 30 minutes on a mechanical shaker and later contents were centrifuged to separate clear extract (Jackson 1973). Exchangeable K was determined by extracting the soil with neutral normal ammonium acetate, Non-exchangeable K was estimated as the difference between boiling 1N HNO3 –K and neutral normal ammonium acetate K (Thomas 1982).
Results and Discussion: The result showed that for most of the studied soils, long-terms horticultural practices decreased the amount of different K forms as a result of changes in soils types, agricultural practices and soil properties. In Comparing to the virgin soils, long-term horticultural and irrigation activities caused a decrease?? in soluble K from 0.05 (a drop of 15% with depletion factor of 0.85) to 1.48 mmol l-1(a drop of 95% with depletion factor of 0.05), potassium absorption ratio (PAR) from 0.08 (a drop of 31% with depletion factor of 0.69) to 1.17 mmol l-1(a drop of 97% with depletion factor of 0.03), exchangeable K from 12.01 (a drop of 3% with depletion factor of 0.97) to 285.98 mg kg-1 (a drop of 97% with depletion factor of 0.43),exchangeable potassium percentage(EPP) from 0.49 (a drop of 12% with depletion factor of 0.88) to 3.47% (a drop of 59% with depletion factor of 0.41), available K from10.42 (a drop of 3% with depletion factor of 0.97) to 180.65 mg kg-1(a drop of 53% with depletion factor of 0.47) and non-exchangeable potassium from 43.05 (a drop of 8% with depletion factor of 0.92) to 114.65 mg kg-1 (a drop of 19% with depletion factor of 0.81). Isotherm studies showed that the uptake of potassium in gardened series were more than virgin soils. The highest adsorption values were observed in VerticEndoaquepts (gottape) subgroup.In this series of soil, amount of available k (potassium soluble + exchangeable K) and expandable clay increased by long-term horticultural practices which can be effective in increasing K buffering capacity.
Conclusion: long-term horticultural practices decreased K in soil solution and potassium adsorption ratio. The main reasons for the decline of soluble K can be explained by possible movement of K into the depths, dense cultivation and harvesting crops as well as high levels of calcium and magnesium in irrigation water of study area.In comparison with adjoining virgin soils, horticultural practices caused significant decrease in the amount of exchangeable K, exchangeable K percentage (EPP) and available K. The most important cause of reduced exchangeable potassium may be related toK uptake by apple trees (The study area is generally under the apple orchard user) which had the great need for K. Consequently, due to lack of fertilizers application and agricultural practices,the amount of available K declined in soils about 80percent. On the other hand, In the Non-exchangeable K amount with long-term horticultural practices non- significant reduction occurred. Since the amount of exchangeable and available k in these soils is high, it seems to be enough to satisfy the needs of the regional products.
کلیدواژه‌ها [English]
- Isotherms of potassium adsorption
- Long-term Horticatural
- Urmia plain
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