تغییرات زمانی و مکانی برخی از ویژگی‌های خاک در مزارع زیر کشت گندم در استان خوزستان

با بررسی تغییرات زمانی و مکانی ویژگی‌های خاک می‌توان پتانسیل و محدودیت‌های موجود برای توسعه کشاورزی پایدار را شناسایی نمود. این پژوهش با هدف بررسی تغییرات زمانی و مکانی برخی از ویژگی‌های خاک در زمین‌های زیر کشت گندم در استان خوزستان انجام شد. داده‌ها از 15 شهرستان استان خوزستان شامل 212 و 718 نمونه خاک از لایه 0 تا 30 سانتی‌متری مزارع گندم به‌ترتیب در سال‌های 1390 و 1400 جمع‌آوری شدند. مقادیر ph، کربنات کلسیم معادل، شوری، کربن آلی، فسفر و پتاسیم قابل دسترس خاک در نمونه‌ها اندازه‌گیری شدند. نتایج نشان داد که میانگین کربنات کلسیم معادل در خاک‌های مورد بررسی برابر %46/3 و میانگین ph خاک‌ها برابر 7/4 بود. از سال 1390 تا 1400، زمین‌های زیر کشت گندم دارای خاک با محدودیت شوری (> 4 ds m^-1) از 42 به 59 درصد افزایش یافته است. با وجود این‌که، بیش‌ترین میانگین شوری خاک (بیش از ds m-1 12) در بخش‌های جنوبی استان خوزستان و به‌ترتیب در شهرستان‌های شادگان (ds m^-1 16/2) و هندیجان (ds m^-1 14/2) مشاهده شد اما بیش‌ترین نرخ تغییرات زمانی شوری خاک در شهرستان گتوند (209 درصد افزایش) و بهبهان (191 درصد افزایش) رخ داد. با گذشت ده سال، میانگین درصد کربن آلی خاک در مزارع گندم استان به میزان 0/1 (از 0/76 به 0/66 درصد) کاهش یافت و مزارع دارای محدودیت کربن آلی خاک (کم‌تر از 1 درصد) از 77 درصد در سال 1390 به 90 درصد در سال 1400 رسید. تغییرات زمانی فسفر و پتاسیم قابل دسترس خاک در مزارع گندم به‌ترتیب در 80 و 67 درصد از شهرستان‌های مورد بررسی معنی‌دار نبود. نتایج نشان داد که علی‌رغم متفاوت بودن نرخ تغییرات زمانی و مکانی ویژگی‌های مختلف خاک، به‌طور کلی مدیریت‌های رایج در کشت گندم موجب افزایش محدودیت‌های خاک با شدت‌های متفاوتی شده است که می‌تواند پایداری تولید در کشاورزی استان را به‌شدت تحت تاثیر قرار دهد.  

the temporal and spatial variations of some soil properties in wheat-cultivated farms of khuzestan province

abstractby evaluating the temporal and spatial variations of soil properties, it is possible to identify the existing potential and limitations for the development of sustainable agriculture. this research was conducted with the aim of investigating the temporal and spatial variations of some soil properties in wheat-cultivated lands of khuzestan province. two sets of soil samples including 212 and 718 samples were collected from surface soil (0‒30 cm) in wheat farms of khuzestan province (15 cities) on 2011 and 2021, respectively. the soil ph, calcium carbonate equivalent, salinity, organic carbon, and available phosphorus and potassium were measured in the samples. the results showed that the average calcium carbonate equivalent in the studied soils was 46.3% and the average ph of the soils was 7.4. the results showed that the wheat-cultivated lands with soil salinity restrictions increased from 42 to 59% in ten years past. although, the highest average soil salinity (> 12 ds m-1) was revealed in the southern parts of khuzestan province and in the cities of shadgan (16.2 ds m-1) and handijan (14.2 ds m-1), respectively, but the highest rate of temporal changes of soil salinity occurred in gotvand (209% increase) and behbahan (191% increase). moreover, the average of the soil organic carbon content in the wheat fields of the province decreased by 0.1% after ten years (from 0.76 to 0.66 %), and the fields with restriction of the soil organic carbon (less than 1%) increased from 77% on 2011 to 90% on 2021. temporal changes of soil available phosphorus and potassium in the wheat fields were not significant in 80 and 67% of the studied cities, respectively. the results showed that despite the different rates of temporal and spatial changes of various soil properties, in general, agricultural management of wheat-cultivated farms in the last decade has increased soil limitations with different intensities, which strongly affects production sustainability in agriculture of the province.background and objective: by determining the temporal and spatial variations of soil properties, it is possible to identify the existing potential and limitations for sustainable agricultural development (tumsavas et al., 2019). in addition to indicating soil ecosystem services and functions, soil properties also reflect soil response to different farm managements (lehmann et al., 2020). therefore, this research was conducted with the aim of investigating the temporal and spatial changes of some soil properties in wheat-cultivated lands of khuzestan province.methods: two sets of soil samples including 212 and 718 samples were collected from surface soil (0‒30 cm) in wheat farms of khuzestan province (15 cities) on 2011 and 2021, respectively. soil properties including ph, calcium carbonate, electrical conductivity of saturated extract (salinity), organic carbon, available phosphorous, and available potassium were measured. the spss v.19 statistical software and independent t test at the probability level of 5% were used to determine significant temporal variation of soil properties. moreover, mapping and spatial variations of soil properties were determined by gis v.10.3 software.results: the results showed that the mean of calcium carbonate content in the wheat-cultivated soils of khuzestan province was 46.3% and the mean value of soil ph changed from 7.43 to 7.48 in 2011 and 2021, respectively. in 2011, about 42% of the wheat-cultivated lands faced soil salinity restrictions, but after ten years, this limitation reached to 59% of the wheat-cultivated lands in khuzestan province (i.e., 23% increase). the results revealed that the means of soil salinity in the central part of khuzestan province, including ahvaz, bavi and shushtar, ramshir and mahshar were less than 4 ds m-1, while shadegan, hendijan and ramhormoz (southern part of the province) had a mean value of soil salinity more than 12 ds m-1. the evaluation of temporal variations in soil salinity over a ten-years period showed that there was no significant variation in the 11 studied cities. while a significant increase in the mean soil salinity of wheat-cultivated farms was observed in four studied cities involving omidie (89%), ramhormoz (171%), behbahan (191%) and gotvand (209%). the mean soil organic carbon content decreased from 0.76 to 0.66 % and only 23 and 10 % of the studied soil samples in 2011 and 2021, respectively, had soil organic carbon content more than one percent. within a period of ten years, four cities of khuzestan province (in the northern and southern parts) including shush (15%), shushtar (32%), handijan (21%) and mahshahr (29%) showed a significant decrease in soil organic carbon content. the results showed that the temporal changes of soil available phosphorus and potassium were not significant in 80 and 67% of the studied cities, respectively. a significant decrease in soil available phosphorus was observed in shushtar city (31%) and a significant decrease in soil available potassium was also highlighted in shush (25%), mahshahr (18%) and hoizeh (15%) cities.conclusions: the results showed that the mean value of soil salinity in the two cities of gotvand (with soil salinity less than 4 ds m-1, and 0.5 to 1% soil organic carbon) and behbahan (with soil salinity level in the range of 4‒8 ds m-1, and organic carbon content of 0.5 to 1%) is in a caution condition. however, the trend of soil quality degradation in the wheat-cultivated fields of these two cities is very severe (209 and 191% increase in soil salinity of gotvand and behbahan, respectively). the results showed that despite the different rates of temporal and spatial changes of different soil properties, in general, agricultural management of wheat-cultivated farms in the last decade has increased soil limitations with different intensities, which strongly affects production sustainability in agriculture of the province.references:1. lehmann, j., bossio, d.a., knabner, i.k., rillig, m.c., 2020. the concept and future prospects of soil health. nat. rev. earth environ. 1, 544–553. doi: 10.1038/s43017-020-0080-8.2. tumsavas, z., tekin, y., ulusoy, y., mouazen, a.m., 2019. prediction and mapping of soil clay and sand contents using visible and near-infrared spectroscopy. biosys. eng. 177, 90–100. https://doi.org/10.1016/j.biosystemseng.2018.06.008.