جستجوی مقالات مرتبط با کلیدواژه « micro » در نشریات گروه « آب و خاک »

This study was conducted to investigate the type and origin of clay minerals via several profiles in Lordegan hilly lands. The profiles were located in two kinds of land uses including forest and dry farm at different slope positions as sampling sites. The soil saples were collected from two depths of soil horizons to indicate CEC, soil texture, OC%, calcium carbonate equivalent, X-ray diffraction and micro-morphological study via undistributed soil sampling. The results illustrated that the dominating clay minerals are Illite، Smectite, Chlorite and Chlorite-Smectite as mixed minerals. According to the result, the origin of minerals in both land uses and different slope positions is inheritance from parent material. These minerals are mostly apparent in lower positions of the slope especially rain feed. Thin sections investigation of some horizons in the both land use in different slope positions showed that there was no difference regarding the kind of soil voids and C/F ratio between two sampling sites. (including land use and slope positions). Complex packing voids, Vugh and planar voids were the most dominant voids of these profiles. The observed b-fabric in all horizons was crystallitic and soil structure in back slop was subangular blocky. In all horizons of rain feed land use except for shoulder and back slop, clay films and calcite coatings were observed.

Appropriate nutrition is necessary for obtaining high quality crop. In this research، the effect of different NH4+ / NH4+ + NO3- ratios on vegetative growth and N، K، Ca، Mg، and Fe concentration in apple seedling leaf was studied. The NH4+ / NH4+ + NO3- ratios were (0. 03، 0. 07، 0. 10، 0. 14، and 0. 04 meq L-1). Nutrient solution pH was adjusted at 6. 5 ± 0. 1. The experimental design was randomized complete block and was performed in three replicates. The results of the evaluation indicated that the increase in ammonium concentration caused significant (at 5% level) increase in leaf area، stem length، branches current year length، moisture content، and iron concentration of leaf. However، stem diameter، calcium، potassium، and magnesium concentration of leaf showed significant decrease with increasing concentration of ammonium. Number and diameter of current year branches as well as total nitrogen concentration did not show significant differences under different NH4+ / NH4+ + NO3- ratios.

Determination of crops water requirement in different environmental conditions is essential for preparation of precise and suitable irrigation scheduling. The effect of soil compaction and texture on crop coefficient and evapotranspiration of maize was investigated in this study, which was conducted as a factorial experiment with a completely randomized design in a research farm in Jey and Qahab district in Isfahan. The study included three soil texture treatments of silty clay loam, loam, and sandy loam, and three compaction treatments including natural density of field soils, compaction by dropping 2.5 kg weights 25 and 50 times (based on the standard Proctor test). In order to determine the reference evapotranspiration of maize, evaporation pan method was used, and for actual evapotranspiration, volumetric soil water balance method was adopted by using micro-lysimeters-drains (32 cm diameter and 80 cm height). The results showed that by increasing soil compaction crop evapotranspiration and crop coefficient of maize were reduced at the different growth stages. The maximum 10-day average evapotranspiration of maize was obtained at 8.76 mm/day in silty clay loam soil with natural bulk density of 1.27 g/cm3. This value was 70 percent higher than the minimum 10-day average evapotranspiration in the fifth decade of growth. Increasing the soil bulk density decreased total crop evapotranspiration 23%, 20.8%, and 12.8% in loam, silty clay loam, and sandy loam soil, respectively. The maximum and minimum impact of soil bulk density on crop coefficient of maize was observed in the middle and initial growth stages, respectively. The maximum and minimum impact of increased soil bulk density on reduction of crop coefficient of maize in the middle growth stage was 40.3% in loam soil and 20.7% in sandy loam soil for the second bulk density treatment.

The objective of this study was to evaluate the effects of crop residues management on soil physical and biological properties. The impacts of residue management on yield of forage corn and barley and soil micro-organisms population were also studied. The results showed that application of crop residues increased soil organic matter (22.2 %), saturated hydraulic conductivity (51.9 %), porosity (3.7 %), mean weight diameter (MWD) of the aggregates (5.4 %), and field capacity (5.8 %) and decreased bulk density (3.7 %) Whereas crop residues burring decreased soil organic matter (31.8 %), saturated hydraulic conductivity (36.6 %), porosity (0.5 %), mean weight diameter (MWD) of the aggregates (5.1 %), and field capacity (4.1 %) and increased soil bulk density (1 %). Soil water characteristic curves showed that the observed differences in soil water retention of application and burning residues treatments were higher at low matric suctions than those at high water matric suction. The results demonstrated that micro-organisms population significantly (P<0.05) decreased in residues burning treatment compared with the residues application treatment. Therefore, based on the results of this study residue's burning is not recommended in Ardabil.

Due to high variability and complexity of the soils, direct measurement of hydraulic parameters is difficult, time-consuming and expensive. Therefore, these properties are estimated using indirect methods. In this study, 74 soil samples were taken from Guilan province, and particle (PSD) and micro-aggregate size distribution (MASD), bulk density and water content at matric suctions of 2, 5, 33, 100 and 1500 kPa were measured. Fractal parameters of soil PSD and MASD and particle’s size distribution parameters of Fredlund’s model were calculated and used to estimate water content at different matric suctions. The results showed that entering fractal parameters of PSD did not improve the estimation of water content. By adding fractal parameters of MASD to the model, estimation of water contents at different matric suctions was improved significantly (P<0.05) and the root mean square error (RMSE) value decreased by 6.5% for the validation step. This may be the result of the influence of soil structure on water retention. But using of PSD parameters of Fredlund’s model was more effective in estimation of water content and decreased the RMSE of validation step up to 27.0%. The best estimation of water content was observed at the matric suction of 5 kPa, in which the coefficient of determination of training step increased by 0.36. It may be due to the large number of parameters of Fredlund’s model and better simulation of PSD. In general, using parameters of PSD and MASD improved the estimation of soil water retention curve.

In this study the effects of irrigation with raw or diluted municipal effluents along with foliar micro-nutrients fertilizer spray were examined on the growth, yield and mineral nutrient in foxtail millet plants. The experimental design was a split-plot with three irrigation sources (namely raw sewage, 50% diluted sewage and well water) as main-treatment and four combinations of Mn and Zn foliar spraying as sub-treatments, which were applied with three replications. The experiment was conducted at the Zabol University research farm during 2009. The applied municipal effluents contained higher levels of macro and micro-nutrients than the well water. The experimental results indicated that irrigation of plants by raw or diluted sewage improved the measured growth parameters and productivity of foxtail millet plants. In addition macro and micro-nutrients concentrations were improved. These improvements were attributed to the presence of high levels of essential nutrients such as nitrogen, phosphorus, and organic matters in wastewater. Manganese and Zn supplied through sewage water alone were not able to raise the productivity of millet to the level obtained through fertilizers at the recommended level, which indicated that additional nutrients through fertilizers are required to obtain higher productivity of millet under sewage farming. Despite the differences in nutrients concentration among different irrigation water sources, the micro-nutrients foliar spray did not affect concentration of macro and micro-nutrients in foxtail millet plant. Overall, the results suggest that municipal sewage could be efficiently utilized as an important source of water and nutrients in growing foxtail millet Sewage water irrigation did not have any appreciable harmful effect on crop productivity.