پديد آورندگان :
اميرپور، زهرا نويسنده , , رضاپور، سالار نويسنده , , دولتی، بهنام نويسنده استادیار گروه خاكشناسی dovlati, behnam
چكيده فارسي :
فرآیندهای فیزیولوژیكی و زیستی متعدد در گیاه، تشكیل كربوهیدرات¬ها و پروتئین، فعال¬سازی حدود 50 آنزیم برای نقل و انتقال انرژی همچنین كاهش هدررفت آب از منافذ برگ، تحت تأثیر حضور پتاسیم در گیاه است (16). عملیات باغداری طولانی¬مدت ممكن است بعضی تغییراتی را در ویژگی¬های جذبی و توزیع شكل¬های پتاسیم ایجاد كند. برای بررسی این فرضیه، خاك¬های سطحی 5 زیرگروه از 15 سری خاك باغی و بكر هم¬جوار در جنوب دشت ارومیه كه برای مدت بیش از 5 دهه تحت عملیات باغداری طولانی¬مدت قرار گرفته¬اند تشریح و نمونه¬برداری شدند. نمونه¬های خاك پس از هوا خشك شدن و عبور از الك 2 میلی¬متری تحت آزمایش¬های مختلف فیزیكوشیمیایی قرار گرفته و شكل¬های مختلف پتاسیم و هم دماهای جذب پتاسیم تعیین شدند. نتایج نشان داد كه در بیشتر خاك¬های مطالعه شده عملیات باغداری طولانی¬مدت به تبعیت از تیپ¬های مختلف خاك، فعالیت¬های باغی و خصوصیات خاك باعث كاهش پتاسیم محلول از 05/0 تا 48/1 میلی¬مول در لیتر، پتاسیم تبادلی از 01/12 تا 98/285 میلی¬گرم بر كیلوگرم خاك، پتاسیم قابل استفاده از 42/10 میلی¬گرم بر¬كیلوگرم خاك تا 65/180 میلی¬گرم بر كیلوگرم خاك، پتاسیم غیرتبادلی از 05/43 تا 65/114 میلی¬گرم بر كیلوگرم خاك، 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 كمترین كاهش را در بین شكل¬های پتاسیم نشان داد. مطالعات هم دماهای جذب نشان داد كه جذب پتاسیم در سری خاك¬های بكر نسبت به خاك¬های باغی بیشتر بوده و در زیرگروه ورتیك اندوآكوئپت (سری قوت تپه) جذب پتاسیم حداكثر بوده است.
چكيده لاتين :
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.
