Soil Physics, Erosion and Conservation
Bahareh Kiani; Farshad Kiani; Azam Rezaee; Pouneh Ebrahimi; Samaneh Mahzari
Abstract
Introduction: Different strategies have been proposed to sustainable soil management, including conservation agriculture. Conservation agriculture is based on four principles. Reducing plowing and soil disturbance, leaving an appropriate amount of plant residues on the soil surface, crop rotation with ...
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Introduction: Different strategies have been proposed to sustainable soil management, including conservation agriculture. Conservation agriculture is based on four principles. Reducing plowing and soil disturbance, leaving an appropriate amount of plant residues on the soil surface, crop rotation with an economic cultivation pattern, and sustainable production of agricultural products with benefits are the basis of these four principles. The economic benefits of conservation agriculture and tillage in the early years have challenges in terms of implementation. There are few studies on the impact of the initial phase of conservation agriculture on soil nutrients and its consequences, so this study aims at the impact of Various protection management on some soil quality indicators during the initial years of implementation. Recently, farmers in Golestan province have been following the conservation agriculture in their fields without implementing a standard method and uniform instructions. Therefore, different results are obtained by implementing conservation tillage methods. In general, the economic benefits of conservation agriculture in the first year of its implementation are very controversial, and farmers think that the implementation of conservation agriculture may not be profitable due to the high consumption of herbicides and low yield, especially in the early years of its implementation.Methods and Materials: This study was conducted in Nokandeh region of Golestan province in the form of a randomized complete block experiment in three types of management including optional(minimum) tillage (MT), Conservation agriculture (CA) and conventional tillage (CT) and in 4 years. In each management, 30 soil samples were selected from the depth of 0 to 20 cm and the indicators were evaluated. Soil pH, Texture, Electrical Conductivity, Total Neutralizing Value (TNV), Soil Carbon, Total Nitrogen, Available Phosphorus and Potassium, and soil micronutrients contain Fe, Mn and Zn were evaluated using scientific methods. Data normality was also tested using the Kolmogorov-Smirnov test. The difference between the means has been calculated using Duncan's test at the confidence level of 0.01 and 0.05. SAS ver 9.4 software was used to analyze the data.Results and Discussion: he results show that the effect of tillage management on pH changes is not significant, while the effect of time on pH changes is significant at the one percent level (p ≤ 0.01). The pH in no-till in the fourth year was (7.64) and minimum tillage (7.62) and conventional tillage (7.4). The lowest pH value was in conventional tillage treatment, which decreased by 3.6 percent compared to the first year. The main decrease in electrical conductivity was observed in no-till, with a 32% decrease in soil electrical conductivity in the fourth year compared to the first year, and the minimum changes were observed in conventional tillage. The amount of organic soil in conservation agriculture and then OC was observed to increase by 47% and 17%, respectively, compared to the first year. The implementation of conservation management in different years was not significant on the amount of TNV, but the percentage of the amount of TNV was observed in tillage managements, CT > CA > CT respectively. The amount of total nitrogen has increased in MT and CA, which means a decrease in nitrogen leaching in four years. Conservation agriculture in the fourth year can increase the amount of available phosphorus in the soil by 47% compared to the first year, and the potassium element has increased by 58% in CA and 52% in MT, while the potassium content has increased by 6%. The elements of iron and zinc in MT and the amount of manganese in CA were higher. The results of the present study showed that the most important management factors affecting the initial years are the amount of soil organic matter. Soil nutrients are sensitive indicators of fertility. Changes in soil nutrients increase with a gentle slope in the initial years. And this trend is sometimes accompanied by uncertainties. There are significant aspects of water, plant, and soil interactions in nutrient cycling, etc., that are still unknown.Conclusion: The results of this study showed that although low tillage and no-till treatments improve soil nutritional and fertility indices compared to conventional tillage, the trend of changes in these indices over time is different, which may discourage farmers and promoters in the early years of implementation. Considering that different results have been obtained in this research, it seems that to achieve better and visible results by farmers, sufficient time is needed for implementation. These findings provide a practical perspective to farmers, promoters and managers to realistically pay attention to the achievements in the early years of implementation. It is suggested that in the initial years of implementation in farms with greater fragility and uncertainty, government support should be provided to reach the final sustainability of the plan.
Mansoreh Bameri; Farhad khormali; Hossein kheirabadi
Abstract
Introduction. Soil is an essential part of the environment. It is important for the production of food and other crops. Soil erosion and sedimentation are complicated and least well-known environmental problems worldwide (Mahmoodabadi et al, 2014). Recently, the application of compounds that modify and ...
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Introduction. Soil is an essential part of the environment. It is important for the production of food and other crops. Soil erosion and sedimentation are complicated and least well-known environmental problems worldwide (Mahmoodabadi et al, 2014). Recently, the application of compounds that modify and improve soil quality and also reduce soil erodibility has been more thoroughly researched. These compounds are known by the common name of soil amendments with a relatively high variety such as gypsum, basanite, zeolite, chemical amendments, organic additives, a variety of chemical, biological and composite polymers, soiltac, fungi, polyvinyl acetate, vermicompost and cattle manure, biochar, straw mulching and cyanobacteria and bacteria (Behzadfar et al, 2017). The objective of this study was to investigate the influence of bentonite clay and slope gradient on runoff and sediment concentration and some hydraulic Characteristics in the Loess soil using a rainfall simulator. Materials and Methods The experiments were conducted using a rainfall simulator at the Soil Erosion and Conservation Laboratory, Gorgan University of Agricultural Sciences and Natural Resources, Iran. The soil used for the experiments is taken from the surface layer (0-30 cm depth) of loess lands from Golestan province (37° 55ʹ N and 55° 29ʹ E). The soil sample at first was air-dried, thoroughly mixed and then crushed to pass through 10 mm sieve size. Experiments were done as factorial based on completely random design with three replications. The factors were the bentonite clay at four level (0, 2, 5 and 10 % weight) and slope steepness at three level (10, 20 and 30%). In all experiments, each soil sample was put in the flume, then was saturated from the bottom for 24 h. Afterwards, the drainage water was removed out of the tray, and the experiment lasted for 45 min. For each rainfall event, the sediment-laden overland flow was sampled at selected time intervals and volumetrically measured. The sediment-laden overland flow was sampled at several time intervals and the sediment concentration was determined . The sediment in the collected samples was allowed to settle, separated from the water, and dried in an oven at 105 °C for 24 h. The sediment concentration was determined as the ratio of dry sediment mass to sampled runoff volume for each time interval.Different hydraulic parameters including flow depth, shear stress, stream power, and unit stream power were measured.Results and Discussion The result showed that the sediment concentration decreased with increasing levels bentonite at all slopes. At 10 % slope steepness, the mean sediment concentration varied 32.48 in the control treatment to 24.67 kg m-3 at level 3 bentonite treatment. At 30% slope the corresponding value were 474.52 and 224.14 kg m-3. Therefore, with increasing slope steepness the sediment concentration increased. Totally, the use of bentonite at level 10 % weight could decrease 46% of sediment concentration in comparison with control treatment. Defersha and Melesse (2012) found that rain intensity and slope gradient had significant influences on sediment concentration. Slope gradient is important as more soil particles are splashed down-slope than up-slope (Dunne et al. 2010; Grismer 2012). According to Fig. 2, the obtained flow depth was 1.92×10−4, 1.92×10−4, 1.92×10−4 and 1.92×10−4 m for 0, 2, 5, 10% clay treatment, respectively. Also, the depth flow ranged from 3.6×10− 4 to 1.96×10−4 m on 10 to 30 % slopes. Totally, the depth of flow decreased with increasing slope steepness for all treatments. In fact, due to higher flow velocities at steeper slopes, shallower flow depths were achieved. Statistical analysis (Table 2) confirmed a significant positive main effects of application levels of bentonite and slope on shear stress, power flow and unit power flow. The clay treatment showed significant reductions ranging from 2 to 50% compared to the control treatment for all slopes. Unit stream power varied from 0.0084 to 0.0095 ms-1, 0.0176 to 0.0241 ms-1 and 0.030 to 0.057 ms-1 for 10, 20 and 30 % slope, respectively. Totally, with increasing slope steepness, all the hydraulic parameters, except flow depth, increased. While with increasing percentage of bentonite clay, shear stress and depth flow and stream power, decreased. Consequently, the maximum values were observed at the steepest slope (30 %) and control treatment (0%). Conclusion Based on the results obtained during the present study, it can be concluded that the bentonite can be considered as an effective modifier of soil physicochemical properties leading to better performance in soil and water conservation in loess lands. Keywords: Bentonite, Simulator Rain, Slope, Sediment Concentration, Hydraulic Characteristics
