مجله مدیریت اراضی
سال هفتم شماره 2 (پاییز و زمستان 1398)

The present study aims to investigate the factors affecting farmer attitudes toward sustainable soil management. The statistical population (N=7931) included all the farmers in Divandarreh Township, Kurdistan Province, Iran. Using Cochran's sampling formula, the sample size was estimated at 126 and the respondents were selected using the stratified random sampling method. To enhance the reliability of research findings, 165 questionnaires were administered among the farmers, out of which 150 were ultimately completed for analysis by SPSS software. The questionnaire was used as the main research instrument whose validity was confirmed by a panel of experts and its reliability was established by calculating Chronbach's Alpha Coefficient (α>0.7). Results of means comparisons showed significant differences in farmers' attitudes based on the two variables of participation in extension and training courses and holding non-farm occupations. Results of correlation analysis showed that farmer attitude was positively and significantly correlated with the respondents’ income level, previous farm work experience, farm size, level of education, access to mass media, concern for environmental issues, level of motivation for participating in environmental protection projects, and exposure to education-extension journals in the fields of agriculture and soil management but negatively and significantly correlated with number of land parcels owned. Also, the results of regression analysis showed that the three variables of income level, education level, and access to mass media explained 67.7% of the variance in the dependent variable (i.e., farmer attitude to sustainable soil management).

Quantitative and reliable estimates of soil degradation processes are essential not only for optimizing land management practices but also for ensuring and assessing their effectiveness and the sustainability of the agricultural systems impacted. Application of plutonium (239 + 240Pu) isotopes as new tracers in soil erosion and sedimentation research is a recent development. Compared to other isotopes, these offer such advantages as long half-life, availability in different environments, relatively easy determination methods using highly sensitive techniques, and consistent measurements at reference sites. However, appropriate conversion models are needed to convert the inventory of plutonium (239 + 240Pu) isotopes into soil redistribution rates. Given the few studies reported on the use of plutonium isotopes in soil erosion research, it is natural that only a limited number of models have been so far developed for computing soil erosion rates using plutonium, each of which has its own limitations. This review study will identify and introduce an appropriate model for converting (239 + 240Pu) inventories into soil redistribution rates by exploring the advantages and limitations associated with the models presently available. MODERN is, thus, selected from among the models reviewed and recommended for estimating soil erosion and sedimentation based on its advantages of independence from the type of land use, accurate determination of redistribution in the soil profile, simulation of the exact behavior of fallout radionuclides under different conditions, and its accessible and editable code, all of which make it superior to rival models.

Rather than recording feats of success in using natural resources, some common agricultural practices led to unsustainable agro-ecosystems and environmental crises with negative impacts on both human and animal health as a result of relying on artificial inputs as well as chemical fertilizers and pesticides. This is while food safety and agricultural product quality are major concerns among many middle class and high-income people in most parts of the world. Organic farming is an improved agricultural production method basically founded on no chemical input. According to the statistics released by FAO, the area under rice cultivation in Iran amounted to 556,787 ha in 2016, a large part of which has the potential to grow healthy and organic crops if low-input or non-input methods are employed. Study has shown that the use of chemical fertilizers may be reduced or balanced by applying to paddy fields any of the following either alone or in combination with chemical fertilizers: 2.5 to 20 t/ha of poultry manure, 5 to 20 t/ha of bovine manure, 10 to 40 t/ha of sheep manure, 20 t/ha of green manure, 5 to 10 t/ha of Azolla compost, or 5 t/ha of Ricestraw compost. Application of organic fertilizers seems not only to improve soil physicochemical properties but also significantly reduce (by 70 to more than 90%) the amount of chemical fertilizers used, thereby contributing positively to sustainable rice production.

Piping erosion is an intensifying erosion due to subsurface flow of water whose emergence and development produces significant changes in landscape, causes land and environmental degradation, and leads to soil and water losses. Moreover, this internal erosion causes surface soil fertility to decline, devastates agricultural farms, and poses threats and damages to local people, livestock, farm machinery, and road networks. From a different perspective, however, piping erosion creates natural habitats in its region of impact for the wildlife. The purpose of this study was to identify the advantageous and disadvantageous potentials of piping erosion in parts of the Iranian Loess Plateau in eastern Golestan Province. For this purpose, all the erosion pipes throughout the study area were surveyed using the measurement tape and their characteristics including shrub species, land use, sloping, and geographical location were recorded. Most were found to be rangelands located in concave slopes in the 20‒45% range. Out of the 348 erosion pipes in the area, 133 hosted trees and shrubs such as pomegranate and fig (more specifically, Paliurus spina, Punica granatum, and Ficus). Evidence showed that this type of erosion in Loess deposits created habitats favorable to plant growth and that it might be considered as an opportunity in land management in semi-arid regions to grow native plants and trees.

Employing the Q-methodology, this article addresses the barriers hindering the realization of the participatory management of irrigation water resources as viewed by the executive managers and experts at Gilan Regional Water Authority, Agricultural Jihad Organization, and Gilan University. The research findings indicate that the viewpoints regarding the barriers may be classified into the three institutional-structural, technical-hardware, and cultural-software categories. Accordingly, the following provisions and measures may be proposed to overcome these barriers: 1) Revision and modification of the governance system at the Ministry of Energy to allow for participatory management of irrigation systems; 2) disambiguation of the laws pertinent to water resources in favor of more transparent ones and spelling out the status of the bodies in charge of irrigation; 3) using public-private partnerships to finance schemes designed and implemented to improve and rehabilitate irrigation and drainage facilities; 4) mobilizing public funds toward projects that encourage and attract matching local private investments; and finally, 5) educating farmers and raising awareness among them on government policies and objectives in the field of water, water crises at the global and national levels, the need for transferring irrigation management to users and stakeholders and the principles and objectives behind irrigation associations and bodies.

Supercritical visibility, defined as a 100-meter horizontal field of view (HFOV), is taking an incremental trend in Khuzestan Province due to the increasing development of drought-stricken eroded land as the source of airborne dust, continued drought, and the rising trend in climate change. Surveying the internal land sources of airborne dust, the present study explores the effects of wind direction and speed on this phenomenon in the metropolitan city of Ahvaz. For this purpose, 100-meter HFOVs are initially zoned for a 15-year statistical period to identify the more critical locations in terms of HFOV frequency. Moreover, the long-term annual changes and monthly distributions of the event measured at Ahvaz synoptic station are plotted for the 65-year statistical period of 1952‒2017. Given the significance of steady and calm weather for 100-meter HFOV events, the monthly and hourly events recorded at the station in Ahvaz under steady calm atmosphere are studied. The WR-PLOT software is then used not only to plot the general long-term annual dust rose but also to derive the seasonal distributions of wind direction and speed associated with the events in order to plot and analyze the dust rose for each season. It is found that the annual number of 100-meter HFOV events and its monthly distributions indicate a higher frequency in cold seasons such that the highest number of events belongs to January, December, and February while the lowest belongs to June and July. It is also observed that most dust storms in the warm season have western and northwestern origins while those in the cold season originate from the east and southeast. Due to the heavy air weight and inversion in cold seasons, the 100-meter HFOVs occur mostly at 6 am local time. No significant direct or inverse correlations are observed between 100-meter HFOVs and wind speed due to the dual role of wind in the removal and deposition of dust particles. Overall, 83% of the events are observed to occur during the hours before the noontime and 61.8% of the events occur in very stable weather conditions and calm atmosphere, which allow for the subsidence and deposition of dust particles. Knowledge of the temporal and spatial distributions of supercritical 100-meter HFOVs can be useful for planning operations by the air monitoring and dust control center, flight schedules, and suspension of schools and public offices during critical dust storms.

Water Utility Index (WUI), first introduced by D. White (1958), is defined as one kg of crop produced per one cubic meter of water evpotranspired. This concept was later replaced with the more inclusive one of ‘water productivity’ (WP). The objective behind this latter concept was to provide a measure for interpreting the results of field experiments of water consumption used in making proper provisions for irrigation management, detecting opportunities for water saving and enhancing water productivity, and developing water allocation decision-making support systems. In order to address the water crisis at the national level, the present article presents a detailed definition of the index and the challenges facing its application to develop realistic water saving measures. It is claimed that evaluations solely based on the WP Index, in which the water applied (or, water withdrawn) is the denominator (WPAW), are to some extent misleading. It is argued that the index does not represent real amounts of water saved or effectively used, especially when it comes to the assessment of the so-called ‘water-saving irrigation systems (e.g., pressurized irrigation). To overcome this inadequacy, it is initially proposed that the ET-based WP (i.e., WPET), rather than the plain WP index, should be used for this purpose. In a second stage of the study, a simple computational methodology is developed that is based on the currently available and cost-effective data on ETc and crop yields across the nation (as reported in the national document on water or in the statistical reports on agriculture). As an illustration, the data available on the Karkheh River Basin and the WPET values measured for the major crops of wheat, barely, alfalfa, potato, silage maize, clover, grain maize, sugar beet, onion, tomato, cucumber, and watermelon grown in the basin are computed to be 1.32, 1.49, 1.22, 5.74, 7.93, 1.73, 1.37, 6.17, 6.61, 8.24, 5.07, 6.94, and 2.05 kg/m3, respectively, which are then used to calculate the average value of 2.05 kg/m3 for the whole basin. Finally, WP values reported in the literature and measured using the conventional filed methods (i.e., WPAW) for the above crops grown both in the study basin and across the state are used to derive a proper regression relation between WPET and WPAW, which exhibits a satisfactory goodness of fit (R2=0.96). Using this relation, the average value of WPAW for the basin is obtained to be about 1.20 kg/m3, which is consistent with the values reported elsewhere. Based on the above observations, application of the proposed method as a low-cost and reasonably accurate one is recommended for the estimation of WPET and, thereby, WPAW.

Potential evapotranspiration (PET) is an important parameter of the hydrologic cycle whose estimation is essential for irrigation and water facility schemes as well as drainage and hydrologic studies. The parameter represents potential losses from moist surface soil and vegetation cover. The present study uses different evapotraspiration estimation methods and compares the results obtained from each against those obtained from the FAO-Penman-Monteith method used as the reference in the environment of the Ref-ET software to determine the accuracy of each and to select the best method for estimating PET in Khorrambid Township, Fars Province. All the methods are evaluated in terms of their efficiency using the statistical parameters of Normalized Root Mean Square Error (NRMSE), Efficiency of Model (EF), Agreement Index (d), and Mean Bias Error (MBE). The results are found to rank the investigated methods in the following order: ASCE stPM, ASCE PM, ASCE PMrs, KPen (1972), FAO 24Pn, FP 17 Pen, KPen (1996), Pen (1948), Harg (1985), FAO 24Rd, FAO 24BC, Prs –Tylr, Makk (1957), Turc (1961), and FAO Pan in terms of the lowest MBE and NRMSE but the highest EF and d values recorded. Although the Penman-based equations are found capable of yielding more accurate estimates of evapotranspiration rates by using temperature, relative humidity, wind speed, and sunny hours, in the absence of such data, however, it is the Hargreaves-Samani empirical method that can be effectively used to estimate evapotranspiration in Khorrambid Township with a lower error level than other empirical methods.