نشریه پژوهشهای خاک (علوم خاک و آب)
سال سی و پنجم شماره 1 (بهار 1400)

In this study, the effect of fertigation (83.3, 124.8, 166.4 kg Nitrogen per hectar) and “Pit-fertilization” on fruit yield and quality of Hayward kiwifruit was investigated. Control treatment was the common manner of fertilization by local orchardist. The results showed that leaf mineral nutrient elements significantly changed by fertilization treatment. Fertilization with 166.4 kg N /ha and pit-fertilization significantly increased leaf nitrogen, potassium, and calcium, but no significant difference was found between treatments for phosphorus. Furthermore, the highest nitrogen was found in pit-fertilization treatments (1.01%). The highest fruit yield per vine was found in pit- fertilization treatment (56.8 kg/vine) and fertigation with 166.4 kg N/ha (42.82 kg). The mean fruit weight of all fertilization treatments was more than 90 g, which was higher than the control (85.82g). No significant difference was found for dry matter percentage in fertilization treatments, and all were more than 17%, except the pit method treatment. Fruit firmness of fertigation treatments with 83.3 kg N/ha and pit method was more than other treatments: with 7.69 and 7.35 kg/cm, respectively. Fertigation increased fruit soluble solid content (SSC) and resulted in early ripening. In addition, fertigation with 83.3 and 124.8 kg N/ha increased significantly fruit vitamin C. Overall, pit fertilization and fertigation with 166.4 kg N/ha are recommendable due to increasing yield and maintaining fruit quality as well as reducing fertilizing cost and ecological problems.

Heavy livestock grazing is a severe threat to soil quality in the rangelands, particularly in the semiarid regions. However, grazing exclusion is the effective and low cost management measure combating improper grazing impact. The purpose of this study was to investigate the effects of grazing exclusion on soil physicochemical properties in Dalahoo Rangeland, Kermanshah, Iran, and was carried out during 2016-2019. For this purpose, two linear transects were performed in exclosure (Ex) and grazed (Gr) sites. In each transect, 12 sampling points were selected with 250 m interval and soil samples were taken from topsoil and repeated annually. The results of this study revealed that the respective value of soil organic carbon (SOC) in Ex and Gr was 1.10 and 1.09 %, showing no significant differences between them in the first year. However, in the fifth year, SOC was enhanced to 3.70% in Ex, which was significantly higher compared to Gr (p <0.05) and 5.5 times higher than the first year. The bulk density (BD) in the Ex and Gr soil in the first year was 1.56 and 1.57 gcm-3, respectively. Over five year time, the BD of Ex significantly decreased to 1.266 gcm-3, while there was no significant change in Gr site. Furthermore, the respective ratio of coarse soil aggregate (CSA) with > 1 mm diameter in Ex and Gr was, respectively, 9.18% and 8.09% in the first year, while it was, respectively, 30.29% and 6.90% in the fifth year, which was significantly higher in Ex (p<0.05) and indicated 3.3 times improvement through exclosure measure. Finally, the limitation class for soil quality in the Ex was changed from high (1st year) to no limitation (5th year), while Gr site, which was in “high limitation class” in the first year, showed no change during five year. This study demonstrates that five years grazing exclusion significantly improved soil quality.

The qualitative characteristics of forest soils can change under the influence of complex climatic interactions, soil type, management type, and tree species type. The aim of this study was to investigate the variability of soil quality characteristics in two forest plantations of Quercus castaneifolia C. A. Mey and Pinus radiate D. Don in Wood and PaperForests of Mazandaran Province. In both stands, 36 samples were randomly selected for determination of soil physical characteristics, in one season (autumn), and chemical and biological characteristics, in four seasons (autumn, winter, spring and summer). Physical characteristics (clay, silt, sand, moisture, bulk density and lime), chemical characteristics (pH, EC, nitrogen, phosphorus, potassium, carbon to nitrogenratio) and soil biology (soil respiration, microbial biomass carbon, fine root biomass, metabolic rate, and urease enzyme activity) were measured. The results of this study showed that the concentration of nitrogen, phosphorus and enzyme urease activity in oak stands was significantly higher than pine stand (p < /span><0.01), but potassium concentrations were significantly (p < /span><0.01) higher in the pine stand. In all seasons, the rate of soil respiration in the pine stand was higher than in the oak, but this difference was only significant in summer (p <0.05). Characteristics such as carbon to nitrogen ratio, soil carbon, microbial biomass carbon, fine root biomass, and metabolic coefficient were significantly higher in pine stand than in oak in all seasons (p <0.01). The results of this study showed that, in the nitrogen cycle, the oak stand, but in relation to the carbon cycle and global warming, the pine stand had more effects on the soil characteristics. Overall, the practical results of this study suggest that, to improve soil conditions in the degraded forestlands in northern parts of Iran, plantation of oak species is preferred.

The purpose of this study was to use the Multi-Temporal Sentinel-2 images and phenological index in separating and determining the cultivated area of the agricultural land in the Bastam region. To this end, the agricultural crops of the region were identified according to their types and phenological periods comprising apricot, grape, wheat, and forage corn. Three classifiers including support vector machine, maximum likelihood, and minimum distance models and field observations (points and boundaries provided by GPS) were used in order to compile a land use prediction map. Comparison of the accuracy of the three models showed that the support vector machine had the best performance, with overall accuracy and kappa coefficient of 0.86 and 0.82, respectively. The minimum distance model had the lowest classification performance with overall accuracy and kappa coefficient of 0.69 and 0.61, respectively. According to the model of support vector machine, the highest area (3423 hectares) was obtained for wheat, and the lowest was predicted for forage corn (738 hectares). Finally, the results showed that multi-temporal images and the phenological index had an acceptable capability for separation of the crops, prediction of their areas, and making suitable agricultural land use maps for the study area.

Understanding the factors that limit prediction of regional performance of sugarcane crop and improve management practices is essential. The purpose of this study was to select a model that could estimate the potential of sugarcane production by considering the climatic, plant, and soil and terrain characteristics of the region. The study areas in the south of Khuzestan Province included the agro-industries of Amir Kabir, Miza Kuchak Khan, Dabal Khazaei, Salman Farsi, and Farabi. For this purpose, 100 sites in farms of different areas under sugarcane cultivation were studied based on diversity in soil characteristics. The method of this research was done in two hierarchies. In the first stage, estimation of sugarcane production potential using FAO growth model and, in the second stage, estimation of land production potential for sugarcane according to the effect of limiting factors in soil (as calculated using soil index with parametric method) that reduced yield in the first stage. To analyze the data, regression by standard methods, stepwise, and estimation curve were used. In standard and stepwise regression, soil properties were considered as an independent variable and the observed yield was considered as a dependent variable. In the linear, second and third degree estimation curve methods, the observed yield of sugarcane was considered as an independent variable and predicted yield was selected as dependent variable. The results of the first phase showed that the production potential of the FAO growth model was 95.8 tons/ha while the results of the second phase showed that the production potential of sugarcane in the region at different management levels was estimated from 18 to 69.3 tons/ha. Factors of yield reduction included limiting factors such as lime content, heavy and very heavy soil texture, drainage, salinity and sodicity, and lack of proper management. The results of standard and stepwise regression methods showed that the coefficient of determination was 0.52 and 0.49 and the standard error (ME) was 10.13 and 9.77 tons/ha, respectively. Soil properties could predict yield by standard method up to 52% and stepwise method up to 49%. In the estimation curve method for linear model, second degree, and third degree, the coefficients of determination were 0.74, 0.85, and 0.87, respectively, and standard errors were 7.8, 5.8 and 5.3 tons/ha. Therefore, the third degree estimation curve method, which uses the FAO growth model to predict crop yield, has higher accuracy and less error than the standard and stepwise regression model, which use only the effect of land characteristics on the observed yields.

The present study aimed at investigating the transport of lead by colloids in two types of soils with sandy loam and clay loam textures under vermicompost and organic acid treatments. The experiment was conducted in a complete randomized design. Treatments consisted of three factors including soil texture at two levels (sandy loam and clay loam), additive at five levels (50 and 1000 μM levels of oxalic acid, 1% and 2% weight basis for vermicompost, and a zero level as a control), and the amount of leaching water at 10 levels (10 pore volume). PVC soil columns with an inner diameter of 15 cm and a height of 25 cm were prepared and the treatments were applied, then, leaching was performed based on soil suction measurements at different pore volumes. The results indicated that, after the application of vermicompost to the clay loam soil, leaching colloid from the soil increased and the discharged lead decreased. Adding organic acid increased leaching colloid from the soil; however, treating 50 µM organic acids significantly decreased discharged colloid compared to the control and 1000 µM organic acids treatment. The lowest rates of lead discharge were in the control treatment and the more the concentration of the acid, the more was the discharged lead. However, regarding lead discharge, there was no significant difference among the three levels. In the sandy loam soil, the greatest level of colloid transport belonged to the control, and adding vermicompost significantly prevented colloid transport from the soil, which was compatible with the process of lead discharge. Moreover, adding organic acid decreased colloid transport and the greatest rates of the transportation was recorded in the control treatment that was also compatible with the process of lead discharge. Furthermore, the relation between lead and the discharged colloid was only significant in the sandy loam soil. The results of this study showed that the movement of soluble lead in fine textured soils was negligible and insignificant; however, a substantial amount of lead discharge was detected through colloidal adsorption transport in soil columns. Therefore, it may be concluded that such mechanism would result in lead contamination of groundwater in these types of soils.

The aim of this study was to evaluate the potential of uptake of lead, cadmium, manganese and nickel from municipal waste leachate by Vetiver under greenhouse conditions. This research was based on a completely randomized design in three replications with four treatments, including waste leachate with concentrations of 0, 30%, 60%, and 100%. The plants were irrigated at optimum temperature conditions for vetiver (23-23 °C) and based on water requirement for 5 months and 4 watering per week, each time using one liter of leachate. The results showed that there was a significant difference at the level of 1% in the uptake of heavy metals by the plant. Also, with the increase of leachate treatment levels to 60%, there was a significant difference at the level of 1% in root and shoot length. Then, in the treatment with 100% leachate, root and shoot length were significantly reduced. With increasing levels of leachate treatment, the uptake of heavy metals by the plant increased. The highest uptake was by the root with a total average of 200.21 mg /kg in all four treatments. The highest amount of adsorption was related to manganese, lead, nickel and cadmium with averages of 70.70, 52.73, 44.56, and 32.22 mg/kg, respectively. In the shoot, the average of the total uptake of the four elements was 147.93 mg/kg, with the highest averages belonging to manganese, lead, nickel, and cadmium as 53.18, 38.35, 35.13, and 21.27 mg/kg, respectively. The maximum uptake of the four heavy metals in the roots and shoots was related to the treatment with 100%. Also, for all elements in all treatments, the biological concentration factor (BCF) was >1 and the transfer factor (TF) was <1. The results showed that the plant was able to absorb significantly higher amounts of heavy metals at higher concentrations of leachate. Since roots showed greater uptake of the heavy metals in waste leachate than shoots, vetiver plant can act as a phytostablizer and reduce heavy metals mobilization in polluted soil.