اثر بسترهای مختلف بر ویژگی‌های خاک و صفات فیزیولوژیکی گیاهان ختمی (aleca rosea l.) تحت تنش خشکی

کاربرد مواد آلی به‌عنوان یک استراتژی مناسب به‌منظور کاهش تخریب خاک در آب‌وهوای خشک و نیمه‌ خشک ارائه شده است. به‌منظور بررسی اثر آبیاری و بسترهای کشت بر رشد دو اکوتیپ ختمی زینتی، آزمایشی در شرایط مزرعه تعریف شد. تیمارهای آزمایش شامل دو اکوتیپ (مشهد و ̓تهران̒)، سه سطح رطوبتی (80، 60 و 40 درصد ظرفیت زراعی) و چهار بستر کشت (خاک، خاک + کود حیوانی، خاک + شلتوک برنج، خاک + کاه و کلش گندم) بودند. عناصر ماکرو (نیتروژن، فسفر و پتاسیم)، هدایت الکتریکی، ph خاک و صفات فیزیولوژیکی گیاه (نشت الکترولیت، محتوای نسبی آب، پرولین، کربوهیدرات) و وزن خشک اندازه‌گیری شد. نتایج آزمایش نشان داد که اثرات سه‌گانه اکوتیپ× تنش خشکی × بسترهای کشت بر تغییرات میزان عناصر نیتروژن، فسفر و پتاسیم خاک مزرعه در پایان آزمایش معنی‌دار نشد، امّا بیشترین تغییرات این عناصر در بستر خاک + کود حیوانی مشاهده شد و همچنین، این تغییرات در خاک حاوی اکوتیپ مشهد بیشتر بود. میزان شوری بستر خاک + کود حیوانی در هر دو اکوتیپ نسبت به بستر خاک، 78 درصد افزایش یافت. از طرفی، تغییرات اسیدیته خاک در سطح آبیاری 40 درصد نسبت به شاهد کمتر بود و این تغییرات در بستر خاکی 60 درصد کاهش یافت. تمامی پارامترهای فیزیولوژیکی و رشدی گیاهان ختمی تحت تیمارهای آزمایش قرار گرفت و بیشترین میزان شاخص کلروفیل (68)، محتوای نسبی آب (72 درصد) و وزن خشک (95 گرم) در اکوتیپ مشهد تحت تیمار 80 درصد ظرفیت زراعی در بستر خاک + کود حیوانی و بیشترین کربوهیدرات (82 میلی‌گرم در گرم وزن خشک) در اکوتیپ مشهد تحت تیمار 40 درصد ظرفیت زراعی در بستر خاک + کود حیوانی به ثبت رسید. بدین منظور، کاربرد کود حیوانی همراه با خاک با فراهم نمودن عناصر ماکرو اثرات منفی تنش خشکی را کاهش می‌دهد.

effect of different growth medium on soil properties and physiological traits of hollyhocks (alcea rosea l.) under drought stress

introduction climate change predictions indicate that drought and extreme heatwaves will become more frequent and extreme in many regions. drought is the main abiotic stress that severely reduces plant yield across the globe. thus, this may have negative consequences for the agricultural soils, as it limits the availability of water and nutrients to soil microorganisms and plants that develop on these soils. to cope with this situation, the use of organic amendments is the best option. recent studies have shown that the application of organic fertilizers can affect soil moisture and thus, mitigate the negative effect of climate change on that parameter. organic amendments increase soil organic matter content thus improving soil physical, chemical, and biological properties, and therefore, can confer drought resistance to soils. the application of organic residues has been presented as a great strategy against soil degradation in semiarid environments. however, the interactions between organic amendments and drought in hollyhock plants are not fully known. here, we evaluate whether the organic amendment influences the physiological traits of hollyhocks and soil properties under drought conditions. materials and methods the experiment was conducted in the research field at ferdowsi university of mashhad, iran. the experiment consisted of three factors (cultivars, organic amendments, and drought) with organic amendments and drought having four and three levels, respectively. drought treatments were controlled by a tdr at 80, 60, and 40% fc. the three sources of organic amendments were used cow manure, rice hull and wheat straw. seeds were planted in cocopeat, perlite, and peat mixture trays in the greenhouse with an average temperature of 20 °c and under a photoperiod of 14 hours of light and 10 hours of darkness with a light intensity of 400 μmol-1 m2. in the 5-6 leaf stage, seedlings were transferred in pots (18 cm high and 8 cm in diameter) containing field soil. the plants were transferred to the field with four different substrates (field soil, field soil + manure, field soil + rice hull, and field soil + wheat straw) and were exposed to drought stress for one month during the flowering stage. this analysis examined both the physical and chemical properties of the soil, including changes in the macroelements nitrogen, phosphorus, and potassium. results and discussion soil nitrogen changes were significantly affected by the interactions of ecotype with drought, ecotype with the medium, and drought stress with medium. the highest nitrogen changes were recorded in mashhad ecotype under 80% fc. nitrogen content in amended soil had an increasing trend during the experiment, but the amount of nitrogen had a decreasing trend in soil. in all media under stress, the amount of soil phosphorus was increased and the highest amount of phosphorus was observed in soil + manure at all irrigation regimes. the highest amount of potassium in both ecotypes was observed in soil + manure. the amount of potassium in amended soils under stress significantly increased, but in all organic amendments with increasing drought stress from 80 to 40% fc, the potassium content decreased. in both ecotypes, soil salinity was increased in all culture media. han et al. (2016) stated that the amount of nitrogen, phosphorus, and potassium in the amended soil was higher than the substrates containing chemical fertilizer. the medium ec was alkaline at the end of the experiment and the salinity of the culture medium increased compared to the control. this study revealed a negative correlation between electrolyte leakage and dry weight in hollyhock plants. furthermore, all measured physiological and growth parameters were significantly affected by the treatments. notably, the mashhad ecotype grown in soil supplemented with animal manure at 80% field capacity (fc) exhibited the highest levels of physiological traits (spad and relative water content) and growth index (dry weight).the application of manure + soil by providing macro elements reduces the negative effects of drought stress. conclusion the type of crops grown in arid and semi-arid regions should be reconsidered. also, some plants with high water requirements should be replaced with plants with low and unexpected water requirements. because hollyhocks are low-expected plants that grow well in drought areas, so they can be considered as suitable species for cultivation in low-input systems and can tolerate drought situations by 40% fc in amended soil.