تاثیر پلیمر آکواسورس بر برخی خصوصیات فیزیکی و رطوبتی خاک‌های مختلف

یکی از مهم­ترین چالش­های حال و آینده، به ویژه در مناطق خشک جهان، کم ­آبی است. یکی از روش­های بهبود بهره وری آب و مدیریت بهتر آب مصرفی در بخش کشاورزی، کاربرد مواد جاذب رطوبت است. هدف از تحقیق حاضر ارزیابی اثر کاربرد پلیمر جاذب رطوبت آکواسورس بر پارامترهای فیزیکی و منحنی مشخصۀ رطوبتی سه بافت مختلف خاک است. آکواسورس نسل جدیدی از پلیمرهای جاذب رطوبت بر پایۀ پتاسیم است که زیست­ تخریب­ پذیر بوده و فاقد ترکیب مخرب آکریل آمید است. به این منظور، آزمایش­هایی به صورت فاکتوریل در قالب طرح کاملاً تصادفی با 3 تکرار اجرا شد که فاکتور اول چهار درصد وزنی از پلیمر جاذب رطوبت (صفر، 0.5، 1 و 2 درصد وزنی پلیمر/خاک) و فاکتور دوم سه بافت مختلف خاک (لوم­ شنی، لوم ­رسی و رس­ی سیلتی) بود. نتایج بررسی­ها نشان داد که در تمامی بافت­های خاک مورد مطالعه، کاربرد مادۀ جاذب رطوبت و افزایش سطح مورد استفاده، میزان رطوبت را در نقطۀ ظرفیت زراعی و نقطۀ پژمردگی دائم افزایش داده­است. بیشترین مقدار رطوبت قابل استفاده گیاه در بافت­های لوم­ شنی، لوم ­رسی و رسی­ سیلتی به ترتیب به میزان 9.8، 13.8 و 12.7 درصد حجمی و مربوط به کاربرد 0.5­ درصد وزنی مادۀ جاذب رطوبت در این تیمارهاست. کاربرد مقادیر بیشتر سبب کاهش رطوبت قابل استفاده برای گیاه شده­است. بنابراین، با آنکه پلیمر جاذب رطوبت آکواسورس در جذب آب توانایی خوبی دارد، اما در سطوح بالای استفاده اثر بازدارندگی دارد و قادر به تخلیۀ مطلوب رطوبت نیست.

effect of aquasource polymer on the hydro-physical properties of different soils

introduction today, one of the most important challenges of the present and the future, especially in the arid regions of the world, is the issue of water shortage and in some cases the water crisis. one of the ways to improve water productivity and better water management in agricultural sector as the largest consumer of water is the use of super-absorbent materials to improve soil texture, increase soil water retention, reduce erosion and increase germination. the aim of this study is to evaluate the effect of aquasource superabsorbent polymer on physical parameters and soil-water characteristic curves (swcc) of different soil textures.   methodology aquasource is a new generation of potassium-based superabsorbent polymers that are biodegradable and free of destructive acrylamide compounds. in order to evaluate the effect of aquasource hydrogel on hydro-physical properties of soils, some experiments in the form of a completely randomized design with 3 replications was performed. the first factor was different levels of superabsorbent (0, 0.5, 1 and 2% by weight of superabsorbent/soil) and the second factor was three different soil textures (sandy-loam, clay-loam and silty-clay). swccs related to all treatments were determined by determining the moisture content of the samples at different pressures (0, 0.3, 0.5, 1, 3, 6, 9 and 15 bars) using a pressure plate device. then, to obtain the soil moisture characteristic curve parameters  in each sample, two softwares retc (v.6.02) and rosetta (v. 1.1) were used.   results and discussion the results of variance analysis and mean comparisons based on duncan’s test showed that in all soil textures studied, the application of superabsorbent and the increase aquasource amounts, increased the moisture contents at the field capacity and permanent wilting point. however, the highest amount of soil available water for plant use in sandy loam, clay loam and silty clay textures was 9.8%, 13.8% and 12.7%, respectively, and they are related to the use of 0.5% w/w of superabsorbent in these treatments (fig. 1). the use of larger amounts, up to 2%w/w, reduced the soil available water for plant use. this issue can be related to the reducing the interaction of soil particles and polymers with increasing the amount of superabsorbent application in soil. at high levels of superabsorbent consumption, the contact of the hydrogel with the soil particles is reduced, followed by the aggregation of the superabsorbent. this prevents the proper exchange  between the superabsorbent and the surrounding soil, and thus despite the presence of moisture in the soil-superabsorbent system, this moisture cannot be used for the plant, so that in all three soil textures the lowest amount of plant available water belongs to the treatments of 2% w/w of aquasource. the results of statistical analysis for estimating the parameters of the soil-water characteristic curve due to the application of different levels of superabsorbent in different soil textures using two software retc (v.6.02) and rosetta (v. 1.1) showed that the fit the van-genuchten (moallem) model in retc software in all treatments has provided a good approximation of the parameters of the soil-water characteristic curve (r2> 0.98). also, with increasing the amounts of superabsorbent, the accuracy of the model in estimating the parameters decreased to some extent.     conclusions application of aquasource superabsorbent and increasing the application level of this superabsorbent polymer (from 0 to 2% by weight of superabsorbent/soil) in sandy-loam, clay-loam and silty-clay soil textures caused an increase in the moisture content at field capacity and permanent wilting point. application of 2% w/w in sandy-loam, clay-loam and silty-clay soil textures increased the moisture content at the field capacity by about 2.4, 1.6 and 1.5 times, respectively, compared to the control treatments of each soil textures. however, the highest amounts of plant available water in all three soil textures were obtained by applying 0.5% w/w (superabsorbent/soil). application of 0.5% w/w in sandy loam, clay loam and silty clay textures increased the plant available water by about 1.23, 1.19 and 1.12 times compared to the control treatments in each soil textures, respectively. however, the use of larger amounts reduced the plant available water. at low levels of aquasource application, the interaction between the   superabsorbent polymer and the soil particles in the soil/polymer system facilitates the transfer of moisture stored in the superabsorbent to soil particles. however, increasing the application level of this polymer up to 2% w/w has an inhibitory effect and in this case, the interaction between the polymer and soil particles is reduced, which leads to a lack of proper drainage of moisture from the polymer.   acknowledgement the authors would like to thank agricultural engineering research institute for supporting this research.