Iranian Journal of Soil Research
Year:2016 | Volume:30 | Issue:3 |Papers Count:12

Fertilization is one of the main factors affecting yield and quality of kiwifruit. There is little information on fertilization methods effect on qualitative and quantitative characteristics of kiwifruit. Therefore, this research was conducted with the objective of evaluating different fertilization methods-including broadcast application (as control), drill hole fertilization, and fertigation alone or in combination with foliar application-on yield and nutrient content in kiwifruit, at Iran Citrus Research Institute of Ramsar. Results showed that fertilization methods had a significant effect on yield and fruit weight, and the highest amounts were observed in fertigation combined with foliar application. Furthermore, foliar application increased tree yield 157 percent at all treatments. Firmness and total dissolved solid (TSS) decreased by foliar application at all treatments, except for the broadcast that caused an increase. Mineral concentration in fruit was significantly affected by the fertilization methods e. g., foliar application had significant effect on the concentration of potassium (K), calcium (Ca), and nitrogen (N). In addition, the mineral concentration in fruit decreased in the order of K> N> Ca, regardless of fertilization method. The correlation results showed that fruit firmness had significant relation with Ca and negative relations with K/Ca, N/Ca, and (K+N)/Ca. In addition, TSS showed significant regressions with K and N. Since all kiwifruit orchards in the North of Iran are equipped with micro jet irrigation system, fertigation and foliar application not only can save time and money but can also cause an increase in yield and improve fruit quality.

Soil testing has an important role in proper management of plant nutrition in the field. Recommendations based on soil testing results are regional, therefore, these tests and calibrations must be carried out for each specific climatic condition. Bean (Phaseolus vulgaris L. ) is one of the most widely grown crops in Markazi province and has high nutritional value for human. Because of lack of information about zinc critical levels and regional calibration, this study was conducted in Markazi province. Twenty soil samples from different zones of the province were taken from the surface layer with wide range of soil properties and Zn concentration and were prepared for greenhouse cultivation of bean. Greenhouse experiment was conducted as complete randomized design with three replications. Treatments included two levels of zinc (0, 10 mgkg-1 soil). At the end of vegetative stage, plants were harvested and prepared for laboratory analysis. Analysis of variance results showed that effects of soil type and fertilizer were significant on dry matter weight (DMW), Zn concentration, and uptake. Interaction effects of soil and fertilizer were significant on DMW, zinc concentration, and uptake. Results of Duncan multiple range test showed that fertilizer application caused significant differences on DMW, and plant Zn concentration and uptake. Zinc critical level was determined by Cate– Nelson graphic method at 8 mg Zn kg-1 soil (DTPA extraction method). Regression equation showed that available zinc was significantly related to organic carbon content and calcium carbonate equivalent. Relative yield showed significant relation with soil available zinc. Coefficient ‘ c’ in Mitscherlich– Bray equation was 0. 87. Critical level of soil available zinc at 80%, 85%, and 90 % of bean relative yield was obtained as, respectively, 0. 8, 0. 95, and 1. 14 mg Zn kg-1 soil.

Vermicompost is a type of organic fertilizer that contains the necessery nutrients for plant growth. In order to investigate the effect of vermicompost on morphophysiological traist of basil (Ocimum basilicum L. ), an experiment was conducted as factorial arrangement based on a completely randomized design with three replications under greenhouse conditions, in 2012. Treatments included two ecotypes of basil(green and purple) and five vermicompost levels (0, 20%, 40%, 60%, and 80% vermicompost volumetric). The results showed that there was significant difference in the studied traits (p<0. 01): increasing vermicompost persentage to 80% increased the SPAD number by 34%, and the leaf area became seven times larger compared to the control treatment. The effects of ecotypes were significant (p<0. 01) in total wet and dry weights, leaf number, and photosynthesis. The interaction between vermicompost and ecotypes was significantly different in length of inflorescence, length of branches, photosynthesis and stomata conductivity (gs). According to the results, the maximum length of inflorescence and length of branches were obtained in the green basil and 80% vermicompost, corresponding to 8. 7 and 32 cm, respectively. The overall results indicated that the response of growth characteristics and yield of basil plant was significantly affected by the vermicompost application, such that with increase in vermicompost application, growth indices and yield also increased. Based on the results, it is recommendedthat by considering soil condition, water quality, soil analysis results, type of crop, and plant nutrition conditions, about 4 to 8 kg vermicompost per square meter be used every two to three years.

Fulfillment of a suitable tillage methods and crop rotation are two important management factors that can affect soil physical and chemical properties. This investigation was carried out to test the long-term effects of different tillage methods and crop rotation on physical and chemical properties of soil, based on a factorial and completely randomized block experiment with three replications at Mahidasht Agricultural Research Station for 5 years. The experimental variables included three tillage methods (no-tillage, chisel, and moldboard) and three different rotations (wheat-corn, wheat-canola, and wheat-safflower). In this project, in order to examine and determine the changes created in soil organic carbon pool, soil samples were taken from two layers: 0-15 and 15-30 cm. Soil bulk density and organic matter were measured. The result showed that the tillage treatments in the first years did not have significant differences, but in the later years, the tillage factor was significant. Indeed, in the last study years and also in the overall five-year period, using the no-tillage method was much preferable due to improving the soil organic matter pool by about 5. 1 ton per hectare. Application of chisel in tillage system decreased soil organic carbon storage by about 1. 5 ton per hectare. Also, wheat-canola rotation was suitable more than the other rotations. Therefore, adoption of no-tillage together with wheat-canola rotation is recommended for the area in the long term.

Soil organic matter (SOM) is a key index in evaluation of the soil degradation and soil carbon sequestration. Therefore, determination of the SOM spatial patterns is essential for developing the suitable strategies of soil and ecosystem management. Geostatistical methods such as kriging have been widely employed to investigate the spatial pattern of different soil properties like SOM. The quality of the spatial maps is significantly influenced by the statistical properties of the raw data. Thus, identification and elimination of spatial outlier data, which has rarely been considered in previous works, is an important step in preparation of accurate and suitable maps of soil organic matter. The aim of the present study was to evaluate the effect of spatial outliers on the spatial pattern of soil organic carbon at the Rozeh-Chay watershed, Urmia, west Azarbayjan province. A total of 89 surface soil samples (0-10 cm) were collected based on the stratified random sampling scheme. After the normalization of the raw SOM data, global outliers were eliminated by box plot method. Spatial outliers were identified by the global and local Moran’ s I indices. Spatial correlogram of the global Moran’ s I showed the highest spatial autocorrelation at distance of 900 m, which was used as a distance band for preparation of spatial clusters map by local Moran’ s I index. Cluster map of the local Moran’ s I index showed four spatial outliers which were eliminated to assess their effects on the accuracy of kriging map of SOM. With the elimination of the spatial outliers, the MAE and RMSE of the SOM map were decreased from 0. 97 and 1. 31 to 0. 85 and 1. 12, respectively. Therefore, the accuracy of the kriging map increased by 13. 5 percent. Generally, it can be concluded that the combination of Moran’ s I index and kriging method improves the efficiency of organic matter map in the study area.

As an essential micronutrients, iron (Fe) has significant effect on activity of antioxidant enzymes and thereby influences the crop tolerance to environmental stresses. On the other hand, environmental stresses, i. e. air pollution might modify Fe nutritional status of plants by affecting the activity of antioxidant enzymes. The purpose of this study was to investigate the changes in Fe concentration and activity of Fe-dependent antioxidant enzymes in leaves of Plantago major L. with distance from two major sources of air pollution in Shiraz city. Oil Refinery of Shiraz (ORS) and urban traffic of Imam Hossein square were selected as two major air pollutant sources in Shiraz city. Plant leaf samples were collected at different distances from the air pollutant sources. The concentrations of Fe, zinc (Zn), chlorophyll a and b, carotenoids, and activity of catalase and peroxidase in the leaves were measured. The results showed that Fe concentration in the plant leaves increased with distance from the ORS. Leaf Fe concentration was 34. 86% and 44. 73 % higher in the plants at the Rokn Abbad (12 km far from the ORS) town and Melli garden (20 km far from the ORS), respectively, in comparison with those plants close to the ORS. Chlorophyll concentration increased with distance from the ORS. Activity of catalase and peroxidase was increased by distance from the ORS. For the second route, traffic of Imam Hossein square, leaf Fe concentration significantly increased with distance from the source of pollution while no regular trend was found for the changes in chlorophyll concentration and catalase and peroxidase activity. Although many factors including soil properties may be effective in this regard, considering the similarities observed in the characteristics of the studied soils, it can be concluded that there was a close relationship between the Fe nutritional status of Plantago major L. and intensity of air pollution.

Estimation of saturated hydraulic conductivity (Ks) is important as an essential parameter in soil physics. Up to now, a variety of different models have been developed for estimation of Ks which include artificial intelligence (AI) models recently developed for this purpose. Although ROSETTA as an old computer program could simulate soil hydraulic parameter, Fuzzy Inference System (FIS) might be useful to estimate this parameter since it is less time-consuming with lower complexity and cost. A new challenging issue which has received less attention is the uncertainty analysis of the results due to different dataset and different membership functions. In this study, dataset of 151 samples collected from arable land around Bojnourd City in north Khorasan province were analyzed based on stepwise regression and bulk and particle densities determined as the most important inputs to FIS. Monte Carlo simulations of 1000 different samples were achieved and results derived from training period with some available membership functions in Matlab. Totally, three performance criteria showed reliable estimates of hydraulic conductivity for low and high values and, specifically, the best result was obtained from Gaussian membership function.

Zhang's method can be used to analyze the unsteady state flow of water in the soil. The aim of this study was determining a suitable method for estimating the amounts of saturated and unsaturated hydraulic conductivity in pasture, orchards, and other agricultural land uses and how it is affected by land use change. Originally, many orchards and cropped lands were pasture land. Field infiltration rate experiments were conducted using tension disc infiltrometer at tensions of 0, 3, 6, 10 and 18 cm of water with three replications for each land use. Hydraulic conductivity values for different land use were determined by Zhang method. To estimate hydraulic parameters of Van Genuchten soil hydraulic conductivity model in Zhang's method, Rawls et al. and Carsel and Parrish databases, extracted results of ROSETTA code and HYDRUS-2D software were used. HYDRUS-2D inverse modeling method, also, was used to estimate soil hydraulic properties. Relative Error (RE) and root mean square error (RMSE), as statistical parameters were used to evaluate the estimated hydraulic conductivity versus the measured one. Statistical parameters values showed that, in all the three land uses, Zhang model based on Carsel and Parish had the least amount of RE and RMSE and the highest accuracy in estimating the hydraulic conductivity values. In all land uses, other methods (except Carsel and Parrish) performed weakly at low tensions, but results improved at high tensions. During the land use changefrompasturetoorchardandfield crops, saturated hydraulic conductivity valuesincreaseddue toanincrease in soil organic matter in orchards and cropped lands.

The use of municipal solid waste compost has been considered as an appropriate method for the improvement of soil quality in spite of having heavy metals. For this study, three types of soil textures including clay, loam, and sandy loam soil were used. These soils were mixed with five levels of compost treatments (0, 20, 40, 80 and 120 ton/ha) and this research was done using factorial arrangement in a completely randomized design with three replications. After some basic experiments, the content of heavy metals such as Zn, Cu, Ni, Cd, Pb, and Mn were measured in the various sectors. The results showed that increasing the amount of compost application increased the concentration of heavy metals in all solution, organic, carbonate and residual parts of soils as well as soil pH and EC. The increase in the concentration of these elements was more in the clay soil compared to the other two soil textures. Furthermore, the highest amounts of these elements in decreasing order were as follows: residual fractions> carbonate> organic> dissolved parts, respectively. The maximum amount of heavy metals in the solution part belonged to Mn, while Zn accounted for the minimum amount of heavy metal in the sandy loam. According to the results, it is recommended that, in the application of such compost fertilizers, in addition to measuring the heavy metals contents of these fertilizers, the necessary monitoring should be implemented with regular programs.

Low organic matter in arid and semi-arid soils results in decreasing physical quality and increasing runoff and soil erosion. Application of organic compounds (sewage sludge) in these regions can improve soil physical and chemical properties. In the present research, effect of different levels of sewage sludge (0, 30 and 60 ton ha-1) on organic carbon, aggregate stability (mean weight diameter, MWD and geometric mean diameter, GMD), and plasticity limits (upper plastic limit, UPL, lower plastic limit, LPL, and plasticity index, PI) was studied over three time periods of 30, 60, and 120 days after application of sewage sludge. Soil organic carbon increased with increasing sewage sludge, but decreased significantly over time as compared to that of the control. Aggregate stability increased with sewage sludge application. Aggregate stability decreased 60 days after experiment as compared to that of 30 days, whereas, there was no significant difference between the aggregate stability at 120 and 30 days after the experiment. Upper plastic limit increased with increasing sewage sludge application. This criterion increased over time and decreased after that; whereas, LPL increased with sewage sludge application and did not vary over time. Sewage sludge did not affect PI significantly, while PI increased over time and then decreased. In general, results indicated that application of sewage sludge could increase soil organic matter and water holding capacity. Furthermore, with application of sewage sludge, soils can be tilled at higher moisture contents without any probable compaction. Of course, in addition to considering the positive effects of sewage sludge in improving soil physical properties, economical issues and the probable adverse effects of excessive application of sewage sludge and environmental risks should also be considered.

Tree plantations not only alter aboveground vegetation but also lead to significant changes in the physical and chemical properties of soils. Foresters have always relied on a knowledge of chemical and physical properties of soils to evaluate capacity of sites to support productive forests. The purpose of the present study was to investigate flora and plant species diversity in a tree plantation. To achieve this purpose, 20-year old soft and hardwood plantations (Pinus brutia Ten, Cupressus arizonica Green. and Amygdalus scoparia Spach. ) were selected in Reymaleh region, Lorestan province. In each site, 10 plots of 100 m2 (10 ×10 m), totally 30 plots, were randomly selected and then 5 subplots (2. 5 ×2. 5 m) were located in the center and 4 corners of each (n=150). Composite soil samplings were made at 0-30 cm depth in each plot. The results indicated that there was significant difference among stands regarding organic carbon (%) and potassium (p=0. 01) as well as total nitrogen (p=0. 05). The highest organic carbon (%), potassium, and total nitrogen content were observed in Amygdalus scoparia and Cupressus arizonica stands, respectively. There was no significant difference among these stands with regard to pH, bulk density, and phosphorous content.