Iranian Journal of Soil and Water Research
Year:2010 | Volume:41 | Issue:1|Papers Count:15

Nonexchangeable soil-K release rate can significantly affect K dynamics and it's bioavailability during plant growth. In this study, twelve soil samples taken from different wheat cropping regions of Iran were incubated with NaBPh4 to (i) investigate the kinetics of nonexchangeable K release and (ii) to compare the ability of various kinetic equations (zero-, first- and second-order, parabolic diffusion, simplified Elovich and power function) to describe nonexchangeable K release. Results revealed that potassium release was initially rapid followed by a slower rate. Almost 80% of total released soil-K after a time passage of 192h occurred in the first 48hs. The portion of soil total K that was released by NaBPh4 during the 8 day incubation period varied between 12.8 and 55.8% in different soils. NaBPh4-extracted K in a 5min period was highly correlated with NH4OAc-extracted K (r2=0.78, p<0.0001). Results indicated that nonexchangeable K release from most soils has been approximately completed after 96h incubation time. Comparison of coefficients of determination (r2) and standard errors of estimate (SE) showed that the power function, parabolic diffusion and simplified Elovich equations would be of the capability to describe the nonexchangeable K release (r2=0.951 to 1.000). Rate index, as the product of two rate parameters of the power function equation, was highly correlated (r2=0.99) with illitic-K in soils where K release was approximately completed within 192h period. Fit of the data to the parabolic diffusion model yielded two linear relationships with different slopes, suggesting two different rates of K diffusion from soils.

Yazd Asfordi phosphate rock (PR) was partially acidulated at five levels (0, 40, 60, 80, 100%) for increasing the Relative Agronomic Effectiveness (RAE) of canola (Brassica Napus L.), var. RGS in two calcareous and non-calcareous soils. The Partially Acidulated Phosphate Rock (PAPR) was compared vs. the standard fertilizer (triple superphosphate) in two levels (50 and 100 mg P/kg). This study was carried out in greenhouse as a factorial experiment in a completely randomized design, and replicated three times. Results indicated that the relative effectiveness of fertilizers as based on dry mater (DM) and phosphorous (P) uptake significantly (p<0.001) increased with an increase in acidity level. In 0% application of acidulated PR, the relative effectiveness based on DM and P uptake was very low (0.8 and 1.8% respectively). In 100% acidulated PR (in match with single superphosphate) the relative DR and P uptake were 75.7 and 67.5% respectively indicating that DR and P uptake amounts were low as against standard fertilizer application but very high against no PR application, the difference being significant. The relative DM yield in calcareous soil (with low free Fe2O3) was significantly higher than that in non-calcareous soil (with high free Fe2O3). Also, the relative DR yield and P uptake at 100 mg P/kg was significantly higher than that in 50 mg P/kg.

This fertility experiment was carried out using split plots based on a randomized complete block design of three replications in 2006 at Sari Agricultural Sciences and Natural Resources University. The aim of the experiment was to investigate some macronutrient and micronutrient accumulation in leaves of different soybean cultivars as influenced by some organic fertilizer types and levels. Main plots included 8 fertilizer treatments consisting of 20 and 40 tons per hectare of compost, vermicompost and sewage sludge; chemical fertilizer treatment (75 Kg ha-1 of potassium sulfate and ammonium phosphate) as well as control (with no application of organic or chemical fertilizers). Sub plots consisted of three genotypes of soybean (032, 033 and JK). Results showed that maximum grain yield was recorded in levels of 20 and 40 ton ha-1 of sewage sludge (2663.1 and 2842.1 Kg ha-1, respectively), 40 ton ha-1 municipal compost (2791.4 Kg ha-1) and chemical fertilizer (2676.7 Kg ha-1). Among fertilizers 40 ton per hectare of municipal compost, vermicompost and sewage sludge produced significantly higher (P<0.05) grain yield, as well as higher nitrogen, phosphorous, copper and iron content in leaves as compared to other treatments. Ferthermore, maximum grain yield, nitrogen and phosphorous content of leaves were observed in JK (2535 Kg ha-1, 3.9 and 0.25% respectively) and 033 (2667.4 Kg ha-1, 3.7 and 0.26% respectively). The results of mean comparisons revealed that interaction effects of fertilizer and cultivar exerted significant effect on Cu content in soybean leaves so that most Cu accumulations were observed in 032 and 033 lines when 40 tons per hectare of municipal compost was applied. Grain yield had a significant and positive correlation (r=0.35**, r=0.59** and r=0.46**, respectively) with N, P, and K content of leaves.

Salinity and sodicity are the major factors of soil degradation in arid and semiarid areas. The main aim of this study was to evaluate the capability of LISS_III data for soil salinity and sodicity mapping in a selected part of the Qazvin plain, an area of arid environment. During the study, spectral classes were carried out of the remotely sensed data and then with the help of field observations and soil analysis regrouped to soil salinity and sodicity classes. Finally soil salinity and sodicity maps were prepared. Soil sampling was implemented using stratified random sampling method, depending on landscape complexity and homogeneity as well as on the representativity to LISS_III data. Also, in each soil map unit, at least one profile was studied for subsoil salinity variations. Field samples from augur and profiles were analyzed in laboratory for Na+, Ca2+, Mg2+ cations, as well as for soil texture, ECe and pH. The effectiveness of such additional data as digital elevation model and slope which may improve the accuracy of classification was analyzed. Also NDVI, SRVI, PVI, SAVI, SI, BI and NDSI indices as well as, PCA were taken into account in the analysis. Optimum index factor (OIF) was used for a detection of best band combination. Soil salinity map of each selected bands was produced and crossed with the ground truth map. The results indicated that maximum likelihood algorithm is of a higher accuracy than either Box Classifier or minimum distance algorithm. A combination of DEM with LISS_III bands benefits from a highest accuracy. The indices benefitted from an almost high degree of accuracy among the studied processing techniques. The SI and BI indices were in the most correlation with EC and could well distinguish the saline and no saline soils. PCA had a low accuracy in differentiating the saline soils. The optimum index factor had a low overall accuracy. Also results indicated that smooth crusts with no cracks caused increases in the reflections. The accuracy of sodicity map was less than that of the salinity map. The accuracy in moderate sodicity levels was less than in cases with either low or high sodicity levels.

This study is carried out under the assumption that the effective depth of root zone is not restricted to the conventional predefined root depth. Following the reduction of soil moisture within the root zone water uptake potential gradient between the soil in the rootzone and that underneath enables the root to use the available moisture from the soil deeper than the root zone. Based on this assumption, a lysimeter study was conducted in a complete randomized block design of three treatments (A, B, C) and three replications on soybean crop plant. The difference among irrigation treatments was related to irrigation scheduling (amount and interval of irrigation). Treatment A (control) was designed for irrigations when 55% of available moisture was depleted (MAD=55%) and the depth of irrigation was enough only to compensate for moisture deficit. Treatment B (delayed) was set at MAD=65% and net irrigation the same as that in treatment A. Treatment C (excess) was set also at MAD=65% but accompanied by 30% of extra water. The yield under each treatment was recorded and statistically analyzed. Results of soil moisture monitoring throughout the growing season showed that treatment B was faced with water stress due to excess water depletion, delayed irrigation and absence of adequate moisture storage in soil depth. In treatment B, some such yield traits such as number of pods, grain weight in pods, and grain yield were less than those obtained in treatment A. However in treatment C, in spite of the fact that MAD was set similar to treatment B and irrigation interval extended, no signs of water stress were observed in the plants. In addition the yield was not significantly different that that under treatment A. In treatment C, extra amount of irrigation, often assumed to be lost, was preserved beneath the root zone. When water in the upper soil layers was depleted, the reserved water was accessible to the plant which was able to take up the excess water to protect itself from water stress. Such observations show that presence of soil moisture beyond the root zone could be critically beneficial under water stress conditions. Finally, based on the assumed irrigation efficiency of 70% the total amount of applied water would be equal to 404.7 mm. At treatment C, beneficial use was equal to 328.7 mm for which actual irrigation application efficiency would be equal to 81.2%. This comparison shows that from the assumed 30% water loss, an extra 11.2% was available for plant water use. This phenomenon indicates that taking into account of moisture preserved under root zone can somehow increase irrigation efficieancy.

The present study was conducted to evaluate the application of Azotobacter chroococcum inoculants and mycorrhizal fungi Glomus intraradices as well as phosphorus on responses of forage maize in a factorial experiment in completely randomized block design with three replications the study was conducted in Research Station Research Center of Agriculture of Arak in 2004. Under the experimental conditions mycorrhizal fungi caused an increased amount of P uptake, as well as root colonization. Azotobacter caused an increased amount of N uptake too. The different levels of phosphorus caused increased P concentration while decreasing the K and Ca concentration in shoot tissues, increased the amount of P uptake and significantly decreased root colonization. The synergic effects of concurrent application of mycorrhiza, fungus, and Azotobacter cause increased N and P uptake while decreasing root colonization. Application of mycorrhiza along with the third level of phosphorus (100 kg/ha) had the highest effect on P and N concentration and also on the amount of N and P uptake.

Homogeneity and uniformity of soil particles is a most potent factor which affects soil spectral signatures. Geometric standard deviation of soil particles (sg) exhibits the homogeneity of soil components. This study presents the influence of sg on spectral studying of soil geometric mean particle diameter as well as lime. The study was conducted in Pol-e-Dokhtar using the data set of LISSIII-P6, September 7th 2007. Subsequent to satellite data preprocessing, some such processes as: Normalized Difference Vegetation Index, Principal Component Analysis, Soil Line Euclidean Distance and Unsupervised Classification were carried out on the acquired data. By stratified randomized sampling method and according to the false color composite as well as photomorphic units of the main image of the study area, 95 sample points were eventually selected and samples collected from 0-5cm of soil surface. Geometric standard deviation (sg), geometric mean particle diameter (dg) and lime (CaCO3) were later determined for each soil sample in the lab. Samples were accordingly divided into two parts on the basis of the computed geometric standard deviation: the first, sg<10 (homogeneous soil samples) and the second, sg³10 (heterogeneous soil samples). Subsequently via correlation operations in SPSS for both groups, it was expressly displayed that for the first group (sg<10), dg and lime were very forcefully and explicitly correlated with the remotely sensed data, in comparison with the second group (sg³10). Hence, the geometric standard deviation of soil particles (sg) in the study region can powerfully impress soil spectral reflectance.

Constant Rate of Strain (CRS) consolidation is a rapid test method used for determination of compressibility of clayey soils. In a CRS test, the appropriate strain rate is selected based on pore water pressure ratio, i.e. the ratio of pore pressure to total stress. In the present study, to investigate the effect of strain rate on variation of relative pore water pressure, four different clay samples of different plasticity were tested in CRS apparatus. The results of the experiments showed that the trend of variation of pore water pressure is dependent on the drained water flow regime which may be either Darcy or non-Darcy. The results also indicated that the plasticity of the clay has no considerable effect on the variation of the pore water pressure.

In a control structures, it is often preferred to minimize the gate width while utilizing the canal width in full for a stilling basin. Therefore, to reach this, a gradually diverging stilling basin may be used. In this study, the effect of broad-crested sill on the expanding hydraulic jump in a rectangular channel was investigated. A total number of 79 tests were carried out for the range of initial Froude number from 3.1 to 10.3. Sills with various heights and of different locations, relative to the jump toe, were installed in the basins with divergence angles of 3 and 5 degrees. In all the tests, the main characteristics of hydraulic jump including sequent depth ratio, relative length of jump and longitudinal surface profile were recorded. The results indicate that installing broad-crested sills exert an insignificant effect on the sequent depth ratio but may considerably decrease the length of jump. In addition, observations indicate that the increase in divergence angle of stilling basin will increase the effect of sill in decreasing the jump length.

Expansive soils show swelling and shrinkage behavior when subjected to cyclic wetting and drying. The variation in water content influence the volume change in this kind of soil. These volume changes can cause ground movement which may result in damage to the buildings and structures. To study the behavior, a number of successive wetting-drying cycles were conducted on a statically compacted expansive soil in a modified oedometer apparatus. Axial deformations and changes of void ratio as well as the degree of saturation of soil during the drying-wetting cycles were determined according to variation in its water content. Results show that cyclic wetting-drying reduces the susceptibility of soil to swelling. Also variations of water content and void ratio demonstrate that water content-void ratio swell-shrink paths are S-shape curves, while shrinkage of soil occuring in three different phases, happening in specific water content and degrees of saturation.

To analyze and manage the risk of drought in a region, access to some certain information is required, the most important of which is the frequency of drought severity-duration. Realizing the high correlation of these factors, one must pick up a method that pinpoint the relation and effects of these factors on drought analysis. In this paper, numerous copula families were employed to model the correlation structure of variables. Drought data and a three month standardized precipitation index in six stations of Tehran were employed. It is illustrated how to fit a model and compare different copula families to find the most appropriate copula function for the data. Next, by using the best selected copula function, the probabilistic behavior of drought from the severity-duration aspect was modeled based on the observations. The results show the relative closeness of frequencies of drought duration-severity in these stations, so that they can be presented for the province. In addition, the data were also analyzed based on the fitted model and the drought thresholds. That would make the results be more applicable, especially in bringing about the possibility of defining drought scenarios.

Gully erosion is a serious problem for land use/cover in many parts of the world, because of the characteristics of climate, lithology, soils as well as relief. In contrast to sheet and rill soil erosion, relatively few studies have been focused on investigating gully erosion during the last decades. The causes of gully erosion have recently aroused the interest of many researchers in different environments. The ongoing research was applied to two catchments (5397.36 ha) located in Taleghan watershed. The boundary of the gullied area was drawn on orthophoto produced on aerial photographs. Land use/cover map was depicted on satellite images. The digital maps of geology, soil, rainfall, temperature, climate, land use/cover, altitude, slope and aspect were used for a study of their combination in relation with the gullied area. Then the digging of profile was carried out in the region. Results indicate, gullies have been formed on Neogen formation by parent materials of marl, slope less than 15%, southern aspect, humid and semi humid climates. Land use and soils in the gullied area are respectively, rangeland, and Typic calcixerepts and Typic Haploxerepts. The rate of silt is high in the gullied area and the rate of clay has caused increase in soil depth in the gullied area. The rate of gully retreat from 1370 to 1380 is estimated as 3.34 hectares.

One of the most important limitations for selection of second crop in paddy fields in Guilan is waterlogging in the second half of the year. For an evaluation of waterlogging effect (in adequate drainage) on canola yield, a lysimeter study was conducted implementing -10, -5, 0 and +5 cm water level for 2, 5, 7 and 10 day durations at 3 plant growing stages namely: emergence, beginning of flowering and 50% flowering stage in a factorial randomized block design. The variety of canola was Hyola 308. The results showed, increasing waterlogging duration would result in a substantially different lower yield, yield components and other traits except 1000-weight. Increasing waterlogging duration from 2 to 10 days resulted in 19.2% and 8.04% yield reduction and lower oil content, respectively. In addition, for every extra day of waterlogging from 2 to 10 days yield and oil content were lowered by 0.9 g and 0.44%. Yield and 1000-weight were substantially higher as a result of lowering the imposed water level from +5 to -10 cm. Yield and oil content increased by 11.7g and 7.4% when water level was lowered to -10 cm or 0.23 g and 0.15% for every cm of lower water level. Yield, number of sheath, dry matter and harvesting index show no sensitivity to stage of waterlogging. But number of seeds per sheath and oil content were sensitive to waterlogging during the third stage; namely: 50% flowering. One thousand weight was sensitive to waterlogging at the emergence stage.

Application of sulfur as a means of lowering soil pH (even if at micro sites) is one way to increase the availability of insoluble nutrients/ Effectiveness of elemental sulfur in lowering soil pH depends on the activity of sulfur oxidizing bacteria especially, Thiobacillus genus/ To evaluate the possibility of partially substituting sulfur along Thiobacillus inoculum for phosphorus and micronutrient fertilizers, a randomized complete factorial experiment was carried out on Wheat under greenhouse condition/ The treatments included eight levels of sulfur (the rates of sulfur which reacts with 0.5, 1, 2, 4, 8, 12, 16, 20 percent of neutralizing materials), two levels of Thiobacillus inoculum (at rates of 0and 104 cfu gr-1 soil), three calcareous soils with different calcium carbonate content, a control and balanced fertilization based on soil tests/ Following soil preparation and establishment of 216 pots, each fertilizer was applied according to the treatment schedule, and finally 10 germinated seeds of Chamran variety of wheat was planted on each pot/ At the end of the growing season the plants were harvested, then the dry weight, as well as the concentrations of phosphorus were determined in the straw, and grains/Results showed that there were significant treatment effects with respect to dry weight of grain and straw Phosphorus concentration and absorption, in the shoots. Interaction effects of sulfur and thiobacillus inoculum was significant on grain yield, The forth treatment of sulfur in addition to thiobacillus inoculum increased the grain yield 16.7 percent in compare with control.

Soil erosion and its associated land degradation represent major problems for development as well as for environmental resources protection. There is an urgent need to obtain reliable quantitative data on the extent and rates of soil erosion worldwide.The use of 137Cs radionuclide for studying soil erosion and deposition is a valuable tool employed throughout the world. In the present study, use of 137Cs technique as well as proportional, MBM1 and MBM2 models were employed to make measurements of soil loss in Ardal district in Charmahal and Bakhtiari Province. Soil samples were collected from regular grid patterns of 20×20 m. All sample equally weighted 500 g and then 137Cs activity measured through gamma spectroscopy by means of a high-resolution germanium detector. The local reference inventory was estimated at 2130 Bqm-2 with the 137Cs inventories of all soil cores collected from the catchment, ranging from 245 to 4744 Bqm-2. The mean erosion rates for PM, MBM1 and MBM2 models were estimated 20.9, 29.8 and 20.1 t ha-1yr-1 respectively. The overall results indicated high soil erosion rates in the hilly regions of Ardal district. The results of delivery ratio analysis indicated that a high proportion of soil particles are deposited subsequently after initial erosion, not moving to rivers. A Comparison of the three studied models showed that MBM's have estimated soil erosion rate more than PM has. This difference is more pronounced where there are high erosion artes, whereas low differences observed in places of lower erosion rates.