فراتحلیل اثر کاربرد سوپرجاذب رطوبت بر عملکرد گیاهان زراعی در ایران

پژوهش حاضر با هدف فراتحلیل نتایج پژوهش‌های صورت گرفته در کشور و پاسخ به این سوال کلی که آیا کاربرد این مواد به‌طور کلی موفقیت‌آمیز بوده یا خیر و اگر موفق بوده چه مقدار از آن قابل توصیه است، صورت گرفت. برای انجام این پژوهش، مقاله‌های منتشرشده با موضوع تاثیر مقادیر مختلف سوپرجاذب رطوبت بر عملکرد و اجزای عملکرد گیاهان زراعی (شامل غلات، حبوبات، گیاهان دارویی و مرتعی) مورد بررسی قرار گرفتند. نتیجه فراتحلیل نشان داد که میانگین مصرف سوپرجاذب برای غلات، گیاهان دارویی، حبوبات و گیاهان مرتعی به‌ترتیب، 83، 322، 1031 و 210 کیلوگرم در هکتار بود و با مصرف این مقدار سوپرجاذب، میانگین عملکرد دانه در غلات، گیاهان دارویی و حبوبات در مقایسه با تیمار شاهد، به‌ترتیب 13.2، 11.2 و 27.5 درصد (معادل 1059، 345 و 452 کیلوگرم در هکتار) افزایش یافت. به‌طورکلی، نتایج نشان داد که تاثیر سوپرجاذب بر عملکرد دانه و ماده خشک معنی‌دار و بر شاخص برداشت ناچیز است. اندازه اثر کاربرد سطوح مختلف سوپرجاذب بر عملکرد ماده خشک در تمام سطوح بیشتر از اندازه اثر آن بر عملکرد دانه بود. بیشترین اندازه اثر بر عملکرد دانه، مربوط به مصرف 100 کیلوگرم سوپرجاذب در هکتار بود و مقادیر بیشتر از 200 کیلوگرم در هکتار، بر خلاف عملکرد ماده خشک، تاثیر قابل‌توجهی بر عملکرد دانه نداشت. با توجه به نتایج، به نظر می‌رسد که کاربرد 100 کیلوگرم سوپرجاذب در هکتار از نظر میزان تاثیر بر افزایش عملکرد دانه و ماده خشک و جنبه اقتصادی، مناسب‌ترین مقدار باشد.

MetaAnalysis of the Effect of SuperAbsorbent Application on Crops Yield in Iran

Introduction;The most fundamental agricultural obstacle particularly in arid and semiarid regions is water shortage. To mitigate this problem, application of some soil amendments such as water super absorbent polymers (SAP) for increasing waterholding capacity in the soil has been under attention at commercial level in recent years.;Despite numerous studies in Iran and the apparent positive and various functions have been mentioned for SAP and their advantageous in agriculture, there has not been a precise conclusion about these studies. On the other hand, variations in consumption rate, conditions and experimental treatments, makes an impossibility or hardiness to receive a conclusive result for the researchers studying one or few numbers of relevant articles.;  Metaanalysis is the statistical procedure for combining data from multiple studies. When the treatment effect (or effect size) is consistent from one study to the next, metaanalysis can be used to identify this common effect. When the effect varies from one study to the next, metaanalysis may be used to identify the reason for the variation. Decisions about the utility of an intervention or the validity of a hypothesis cannot be based on the results of a single study, because results typically vary from one study to the next. Rather, a mechanism is needed to synthesize data across studies (Rosenthal, 2001). Narrative reviews had been used for this purpose, but the narrative review is largely subjective (different experts can come to different conclusions) and becomes impossibly difficult when there are more than a few studies involved. Metaanalysis, by contrast, applies objective formulas (much as one would apply statistics to data within a single study), and can be used with any number of studies.;Therefore, this study was conducted with the aim of doing metaanalysis on the results of conducted researches in Iran and to answer a general question that whether the application of SAP has been successful or not, and if yes, how much of SAP is recommended.;Materials and Methods;To conduct this research, articles were published during 20062016 with the subject of the effect of different rates of SAP on yield and yield components of crops (including cereals, legumes, medicinal and rangeland plants) were investigated. Amongst 32 articles were checked, 13 articles have enough data to conduct the metaanalysis for seed yield, dry matter yield and harvest index.;Results and Discussion;The result of metaanalysis showed that the mean consumption rate of SAP for cereals, legumes, medicinal and rangeland plants were 83, 322, 1031 and 210 kg ha1, respectively, and with this consumption rate of SAP, the mean seed yield in cereals, medicinal plants and legumes increased by 13.2, 11.2 and 27.5% (equal to 1059, 345 and 452 kg ha1), respectively, compared with control.;Generally, the results showed that the effect of SAP on seed yield and dry matter was significant but was not significant for harvest index. The effect size of the application of different SAP rates on dry matter yield and at the whole levels was greater than its effect size on seed yield. The most effect size on seed yield was considered for the application of 100 kg ha1 SAP and the application rates greater than 200 kg ha1, unlike the dry matter yield, had no significant effect on seed yield.;Conclusions;According to the results, it seems that application of 100 kg ha1 SAP is the most appropriate rate on seed yield and dry matter increment and economical aspects. Design and implementation of the researches focused on estimation and comparison of economic benefits about water consumption as the result of SAP application can justify the relatively high cost of this ecological input and provide the necessary ground for its widespread use by farmers and producers involved in agronomy and horticultural sections.