ارزیابی تاثیر تناوب زراعی بر عملکرد مزارع گندم با استفاده از تصاویر ماهواره‌ای

این مطالعه با هدف بررسی تاثیر تناوب ‌زراعی در مزارع گندم با استفاده از تصاویر ماهواره‌ای در منطقه شاوور استان خوزستان و در سه سال زراعی 1397-1398، 1398-1399، 1399-1400 انجام گردید. نخست پنج شاخص طیفی مورد بررسی قرار گرفت و نتایج برازش نمودارها نشان داد که شاخص ndvi با r^2 برابر 76 درصد بیشترین همبستگی با عملکرد گندم را دارد. سپس به منظور بررسی تناوب های زراعی، ارزیابی ها براساس شاخص ndvi در قالب طرح کاملا تصادفی با سه تکرار انجام شد. تیمارها شامل چهار تناوب گندم-گندم-گندم، گندم-کلزا-گندم، گندم-برنج-گندم و گندم- شبدر-گندم بودند. نتایج تجزیه واریانس نشان داد که میانگین و ضریب پراکنش ndvi تناوب ها در سطح احتمال 1 درصد با هم اختلاف معنی داری دارند. به طوری که از نظر میانگین، کمترین میانگین ndvi در تناوب گندم_برنج_گندم با میزان 0.2650 و بیشترین میانگین در تناوب گندم-شبدر-گندم با میزان 0.5603 میباشد. همچنین از نظر ضریب پراکنش حداقل و حداکثر مقادیر به ترتیب به تناوب گندم-کلزا-گندم با میزان 0.0505 و گندم-برنج-گندم با میزان 0.1970 تعلق داشت. مقایسه متناظر هر تناوب در قبل و بعد از اعمال آن براساس آزمون t-student نشان داد که در تناوب گندم-گندم-گندم و تناوب گندم-برنج-گندم مقدارndvi به ترتیب 10 و 50 درصد کاهش یافت؛ اما استفاده از کلزا و نیز شبدر در تناوب، به ترتیب منجر به افزایش 2 و 30 درصد این شاخص شد. همچنین بیشترین افزایش ضریب پراکنش ndvi در دو حالت قبل و بعد از اعمال تناوب، به تناوب گندم-برنج-گندم، با افزایش 152 درصد، و بیشترین کاهش آن به تناوب گندم-کلزا-گندم، با کاهش 57 درصد تعلق داشت.

evaluation of the effect of crop rotation on the yield of wheat fields using satellite images

introduction achieve more production, efforts should be made to increase yield per hectare. one of the things that play an important role in increasing crop production, disease control, chastity control, improving soil fertility and structure is the implementation of proper crop rotation. crop rotation increases the efficiency of production and yield through the continuity of soil vegetation, more efficient water use, preservation of soil nutrients, increase of soil organic matter and stability of soil grains, reduction of pests and diseases, and better control of weeds. also, data collection in the conducted research is done in a traditional way, which is usually difficult, limited and very time-consuming due to the dispersion of farms and their size. in general, obtaining information and collecting statistics on the characteristics of land resources is of particular importance, and on the other hand, obtaining an information bank in this field, without spending extra money, is possible only by using the science of remote sensing. today, one of the most important topics is the evaluation of spectral indices in terms of their sensitivity to the biophysical characteristics of plants and also the effective factors in the spectral reflections of the crop cover. materials and methods this study was conducted to investigate the effect of crop rotations on wheat yield using satellite images in three crop years 2017-2018, 2019-2028, 2019-2020 in the fields of shavor region of khuzestan province. in this research, all the evaluated images are related to the sentinel-2 satellite and all these images were obtained from the us geological survey website. the satellite images were taken at the flowering stage of wheat, and images without clouds and fog were used on february 25, 2019 (for the year before rotation) and february 19, 2021 (for the year after rotation). also, for pre-processing and processing and extracting information, snap software, sen2cor and envi plugin were used, respectively. the steps of this research were done in three steps. in the first stage, five plant spectral indices evi, gndvi, gari, ndvi and rvi were evaluated to identify the best index to estimate wheat yield. the spectral index, which has a higher correlation with the yield of wheat, was chosen as the base index and was used to continue the research. in the second stage, three farms were randomly selected from each rotation to evaluate wheat yield after their application. in this section, variance analysis was performed in the form of a completely random design in three replications (one replication for each farm). the treatments include four alternations of wheat-wheat-wheat, wheat-canola-wheat, wheat-rice-wheat and wheat-clover-wheat. at this stage, the comparison of means was done by duncan's multi-range test and in the mstatc software environment. the third stage is the changes in wheat yield in each rotation in two times before and after applying that rotation. for this purpose, the changes of the base spectral index before and after the application of periodicity were set as criteria. for this purpose, the average statistical indices and the dispersion coefficient have been compared before and after applying rotation. at this stage, comparisons were made based on the t-student test. in order to have a high repetition and due to the limitation of the number of farms in this benchmark stage, the pixels of farms were considered. results the results of variance analysis of five studied spectral indices in this research showed that the coefficient of explanation of each of these indices with wheat yield at the time of flowering is ndvi with 76, rvi with 73, gari with 71, evi with 60 and gndvi with 57 respectively. in this research, the ndvi spectral index has the highest correlation, r2 of 76%, and the minimum error, rmse of 0.547 earned the results showed that the average and the dispersion coefficient