نشریه پژوهشهای خاک (علوم خاک و آب)
سال بیست و هفتم شماره 4 (زمستان 1392)

The study area is located in south west of Iran، Agili plain، Gotvand، Khuzestan province. Based on Shoushtar synoptic station، the climatic type of the area is semi-desertic. The maximum daily air temperature is 46. 6 °C in June and the minimum daily air temperature is 8. 1 °C in December. The annual rainfall is about 324 mm. The aim of this research was to elaborate an approach for the prediction of the land production potential for irrigated winter wheat، taking into account the environmental condition in the study area. The results showed that irrigated potential yield based on crop growth model method was 8041 kg/ha in the study area and land production potential for irrigated wheat، taking into account the effect of soil limitations، ranged between 2454 to 6687 kg/ha with Square Root method، and between 2296 to 6756 kg/ha for Storie method. The reduction in yield was due to high calcium carbonate، poor drainage، salinity and alkalinity، and management method. For evaluation of the model، three different regression methods، namely، standard multiple regression، stepwise regression، and curve estimation were used for comparison of the yield predicted by the model with the yield harvested by the farmers. Based on the results، coefficient of determination (r2) for predicted yield with Storie، square root، and characteristics methods were 0. 83، 0. 80، and 0. 33. These results show that the predicted yield can estimate the observed yield with 83 percent accuracy for Storie method، 80 percent for Square Root method، and 33 percent for Land Characteristics. Meanwhile، the Root Mean Square Error was، respectively، 598، 648، and 1258 kg/ha. Based on the results، it can be concluded that Storie method can predict yield better that the other methods because of higher coefficient of determination and lower RMSE.

In this research، the effects of variety، water regimes، nitrogen and phosphorus on the concentration، content، and translocation factor of iron، zinc، and manganese in rice was studied in greenhouse conditions in a calcareous soil. This factorial experiment was done in a randomized complete blocks design with three replicates. The factors included two varieties of rice (Hashemi and Ali Kazemi)، water regimes at two levels (continuous submergence and intermittent saturation)، N at three levels (0، 75، 150 mg kg-1) as urea، and P at three levels (0، 25، 50 mg kg-1) as mono calcium phosphate. Having completed 90 days، plants were harvested and total content and concentrations of Fe، Mn and Zn in shoot and root were measured. According to the results، N application caused an increase in Fe concentration of shoot (the above-ground parts)، but caused a decrease in Zn and Mn concentration. However، N application caused an increase in Fe، Zn، and Mn content of shoot. P application caused a decrease in Fe and Zn concentration of shoot، but caused no significant change in Mn concentration of shoot. Also، P application caused a decrease in Fe، Zn، and Mn content of shoot. The result showed that Zn concentration in root and Fe concentration in shoot of Hashemi variety was greater than in Ali Kazemi variety. Fe، Mn، and Zn concentrations in shoot and root in flooded conditions were greater than in periodic saturation. In this research conditions، the content of Fe in shoot and root of both cultivars were not significantly different، but the content of Fe in the shoot and roots of the continuous flooded conditions were greater than the intermittent saturation. In the case of Zn content in shoot and root، there were no significant difference between the two varieties، but the Zn content of shoot was greater under the continuous submergence than in intermittent saturation. Interactions between nitrogen and phosphorus had significant effect on Zn، Fe، and Mn concentrations of shoot and root. Translocation factor of Zn in Hashemi variety was greater than Ali Kazemi variety، but، in the case of Fe and Mn، difference in the translocation factor between the two varieties was not significant. In this experimental condition، translocation factor of Mn was greater than that of Zn and Fe.

Comprehensive evaluation of cultivated soil quality helps to achieve sustainable agriculture. Providing suitable methods for soil quality assessment is essential for management strategies to improve agricultural practices. In this regard، various models of soil quality and feature selection methods were compared to assess the soil chemical and biological quality. Twelve chemical and biological variables were considered as Total Data Set (TDS) and Minimum Data Set (MDS) were chosen by using the principal component analysis (PCA). Four combinations of methods and models for calculating quality and also the most effective indicators for assessment of soil quality and features were chosen. The linear relationships between IQITDS and IQIMDS (R2=0. 883) and between NQITDS and NQIMDS (R2=0. 818) indicated that IQI had better performance for soil quality assessment in the study area. IQITDS index provides more comprehensive and more accurate assessment of soil quality than other indices. However، the use of Minimum Data Set (MDS) reduces workload and costs associated with the care that is appropriate.

Use of salt-tolerant cultivars is one of the ways to deal with salinity. Therefore، in order to investigate the physiological aspects of salt tolerance، a factorial experiment based on completely randomized design with three replications was conducted at the Agricultural Biotechnology Research Institute of Iran in 2010. In this experiment، five fodder plant species collected from saline pasture areas in Iran were evaluated at six different salinity levels (0، 50، 100، 150، 200، and 250 mM). Plants were cultivated in sand culture and were supplied daily by Hoagland solution. Salinity treatments were applied for 21 days at the end of vegetative stage and the shoots were sampled. The results showed that the species Festuca ovina had the highest percentage of fresh and dry weights compared to their control (zero salinity). About RWC، with increasing salinity، four species Hordeum vulgare، Festuca arundinacea، Bromus confines and Agropyron elongatum were able to largely maintain their relative water content (RWC)، while the reduction of RWC in the species F. ovina was maximum (40%) at the salinity level of 250 mM. The results showed that the maximum absorption of sodium was for H. vulgare and then F. arundinacea، A. elongatum، B. confines and F. ovina، respectively. Also، F. ovina had much lower potassium than the other species. Finally، based on fresh and dry weights and osmotic regulation، results showed that H. vulgare was in the first place for salinity tolerance، followed by F. arundinacea، A. elongatum، B. confines، and F. ovina at lower ranks.

In order to increase crop production and its profits per unit area and to control bio-environment and water resources pollutions، producers and farmers need to have information about nutrients accumulation in various plant parts at different growth stages. Proper fertilizer application time is one of the effective factors in increasing fertilizer use efficiency. Meanwhile، determination of mineral nutrients distribution at various growth stages is very useful for proper management and timing of fertilizer application. Therefore، to evaluate nutrient (N، P، K) distribution in various plant parts and determine proper application time and the best management of fertilizer in corn (Zea Mays L.)، this study was conducted in a randomized complete block design with 3 replications. Phosphorus and potassium fertilizers were applied at planting time according to soil test (180 kg ha-1 triple super phosphate and 160 kg ha-1 potassium sulfate). Nitrogen fertilizer (400 kg ha-1 urea) was applied at planting time and as split at two other growth stages (V4 and V7). Plant sampling was performed randomly at different growth stages (3-، 5-، 7-، and 10-leaves stages، tasselling، silking، and maturity stages: V3، V5، V7، V10، VT، R1، and R6). Fresh weight، dry matter، and N، P، K accumulation rate of plant parts (leaves، stems، flowers، ear، and seeds) were determined. According to the results of the experiment، as the growing seasons progressed، plant dry weight significantly increased. Maximum amount of N، P، and K uptake occurred at early growth stages and mostly at 10-leaves stage. At maturity stage، the accumulation of N and P in shoots and leaves decreased while K accumulation in the shoots increased. The main parts of N and P accumulated in seeds، while K accumulated in shoots.

Phosphorus (P) is one of the most important nutrients in crop production. Large amounts of P applied as fertilizer enters into the immobile pools through precipitation reaction with Ca2+ in calcareous soils. In order to economically use the phosphate depositions accumulated in the calcareous agricultural soils and increase the efficiency of P-fertilizers in Iran، an experiment was carried out in the greenhouse of Agricultural College، Tarbiat Modares University، in 2011. The study had a Randomized Complete Block Design with 8 treatments and 4 replications. The experimental treatments were: T1) control، T2) Phosphate Solubilizing Microorganisms (PSM)، T3) Triple Super Phosphate (TSP)، T4) TSP+PSM، T5) Golden Bio Phosphate (GBP)، T6) GBP+PSM، T7) Rock Phosphate (RP) and T8) RP+PSM. The results revealed that P uptake by canola inoculated with phosphate solubilizing microorganisms increased by 80. 44 percent compared to the control treatment. There was a significant difference (p=5%) between inoculated treatments and the control. The highest P uptake was obtained in T4 (TSP+PSM) treatment، which was 84. 57 mg pot-1. Also، the highest amount of relative agronomic efficiency and recovery percent of fertilizer was obtained in T4 treatment، which was 109. 29% and 71. 91%، respectively. Inoculation with phosphate solubilizing microorganisms (PSM) significantly increased dry weight، pod numbers، P concentrations، P uptake، relative agronomic efficiency، and recovery percent of fertilizer in all treatments compared with the control pots. The overall results demonstrated that due to the higher price worldwide of P fertilizers and considering environmental issues، it is recommended that the experiment be further tested in the field.

Effects of different tillage systems on soil bulk density، yield، root growth and nutrient uptake by wheat grain and straw was investigated using an experiment with a completely randomized block design. The experiment had 5 tillage treatments in 4 replications and was carried out in the Research Farm of Gorgan University of Agricultural Sciences and Natural Resources، during the growing season of 2008-09. Tillage treatments were: Moldboard plough at 20-25 cm depth followed by one disc harrowing (MP); Rotary cultivator at 12-17 cm depth (RP); Disc harrowing at 8-10 cm depth (DH); Chisel plow at 25-30 cm depth (CP); and No-tillage (NT). Results showed that، throughout the growing season، the lowest and the highest soil bulk densities at 0-8 cm depth occurred with MP and NT treatments، respectively. At 8-16 cm depth، however، the lowest soil bulk density was observed with MP treatment، except for the stages before tillering and at harvesting stage. Soil bulk densities at 0-8 and 8-16 cm depths gradually increased during growing season in all tillage methods. This increase was less in no-tillage than the other tillage methods. The highest and the lowest values of root weights were obtained with MP and NT treatments، respectively، in stages before tillering and at harvesting stage. The highest nutrient uptake by gain and straw was found in MP treatment with maximum yield. MP raised grain and straw yield by 65. 9% and 58. 61%، respectively، relative to NT. Therefore، MP is suggested as the most appropriate tillage method for optimizing production resources (land، moisture، and soil nutrients).

Quantification of soil water retention curve (WRC) is essential to study soil water movement in unsaturated soils. Direct measurement of soil moisture and matrix potential is too costly and time consuming. Moreover، due to the phenomenon of hysteresis، moisture in the drying branch cannot be used on wetting branch. Therefore، using the indirect method to find the relationship between the two branches of the WRC is needed. Development and use of the pedotransfer function (PTF) is one of the indirect methods. The purpose of this study was to provide a function for the parameters of van Genuchten model estimation in wetting branch using drying branch data. Required information in this research was collected from soil data base (Unsuda). These data include moisture retention curve data of drying and wetting and soil bulk density of 21 soil samples classified in sandy (10 samples)، clay loam and loam (7samples)، and silty clay loam (4samples) texture. To provide the functions، all samples were used. Results showed that nw in van Genuchten model was estimated with good accuracy، while the introduced function for the parameter αw had lower performance. The model obtained for estimation of the parameters of van Genuchten model in the wetting branch of WRC had a higher accuracy in low potentials. Results show that PTF are more powerful than Parlange hysteresis model for estimation of WRC in the wetting branch.

Data on soil hydraulic properties are required to model water movement in soils. Their direct measurements are difficult، time consuming، and expensive، because of high variability and complexity of soil systems. Pedotransfer functions are developed to estimate soil water retention curve (SWRC) using different techniques. In this study، pedotransfer functions were developed to estimate SWRC using the model of Groenevelt and Grant. Sixty nine soil samples were collected from Guilan Province. Soil particles and micro aggregate size distributions، SWRC، and basic soil properties were measured in the laboratory. Fractal and non-fractal models were fitted to the particles and micro aggregate size distributions and their parameters were calculated. Linear regression technique was used to predict the parameters of Groenevelt and Grant’s model. In order to estimate every parameter of the model of Groenevelt and Grant، four pedotransfer functions were developed using each technique and fractal parameters of particles and micro aggregates were used as predictors. Then، estimated parameters were used to simulate SWRC and were compared with the measured SWRC. Fractal parameters of the particle size distribution rendered better predictions of SWRC compared with the other predictors. In spite of the large number of the parameters، using Fredlund’s model did not result in more accurate predictions for SWRC in comparison with using fractal parameters. Probably، these results showed the priority of fractal theory in the particle size distribution and SWRC modeling.

Splash detachment and transport of soil particles by raindrops impacting a soil surface are the initiating mechanisms of water erosion. The aim of this research was to study the interaction effects of land use، slope، and rainfall intensity on splash erosion rate and its components (upslope، downslope transport، and total splash) in Lordegan sub-catchment. A factorial experiment with three variables was conducted in a completely randomized design with three replications using a Multiple Splash Set (MSS) which was designed and manufactured for this experiment. The treatments included three types of land uses (rangeland، dry farming and rain-fed farming)، two levels of rainfall intensity (2. 5 and 3. 5 mm. min-1) and two slopes of 5% and 15%. The rangeland soils showed higher organic matter and mean weight diameter of aggregates (MWD) and lower calcium carbonates than the dry farming and rain-fed farming soils. There was no significant effect of land use on splash erosion rate and its components، but there was a significant effect of slope and rainfall intensity values on the upslope، downslope، and total splash. Also، the interaction effects of rainfall intensity and land use type showed a significant increasing in splash erosion rate and its components. Therefore، increase in splash erosion rate due to rainfall intensity (from 2. 5 to 3. 5 mm. min-1) in irrigated farming land use was 1. 58 and 1. 16 times that of rangeland and dry farming land uses، respectively.

Phosphorus، potassium، and iron are among the essential nutrients that play an important role in plant growth and development. This study was conducted to investigate the proficiency of 7 different strains of bacteria in solubilizing K، Fe، and P from insoluble minerals in laboratory. An experiment based on completely randomized design with four replications was conducted under in-vitro conditions. Treatments consisted of seven bacterial strains and control (non-bacterial). Five strains (JK3، JK4، JK5، JK6 and JK7) were the Bacillus megaterium، while strains JK1 and JK2 were the Lysinibacillus fusiformis and Arthrobacter sp، respectively. Aleksandrov''s medium (MA) supplemented with biotite and Pikovskaya medium (PVK) containing tri-calcium phosphate at concentration of 0. 2% and 0. 5%، respectively، were used to investigate solubilizing ability of the studied strains. Release of K، Fe، P and the final pH were investigated in their culture media. The inverse relationships between the final pH and the amount of soluble P in their Pikovskaya medium was observed، while، after 5 days incubation، there were no significant differences in the decrease in the pH of the liquid medium in biotite treatment. Solubilizing ability of the bacteria was higher in the case of phosphorus than potassium and iron. Compared with the non-bacterial treatment، all strains solubilized significantly (P< 0. 01) higher K and Fe from Aleksandrov''s medium; however، the highest P was observed in Pikovskaya medium. Strain JK7 revealed maximum value of solubilized potassium (3. 1 mg g-1)، but had no significant difference with isolates JK3 and JK6. Also، among the inoculated bacteria، strain JK7 recorded the maximum release of iron from biotite mica (0. 29 mg g-1) in Aleksandrov''s medium and showed a significant difference with other isolates. Strain JK7 recorded maximum release of phosphorus from Pikovskaya medium (61. 26 mg g-1) and showed a significant difference with other strains. Therefore، it can be concluded that the strain JK7 is the most efficient P-، Fe-، and K-solubilizing bacteria under in-vitro condition.

In this study، we tried to study the effect of water spreading on some soil chemical properties in the study region. For this purpose، seven sections of water spreading area were selected and each section was divided into three parts. Soil samples were taken in four replicates from the middle of the three parts at 0-25 and 25-50 cm depths. Then، the samples were mixed. The parts of the study area that did not receive flood water were cosidered as the control. Soil sampling method in the control area was similar to other treatment areas. All samples were analyzed in the laboratory. The results showed that there was significant decrease in pH and lime content at 1% and 5% level، respectively. Also، there was significant (at 1% level) increase in organic carbon، organic matter، and electrical conductivity of saturated extract in the top soil (0-25 cm) in the control area compared to the plots receiving flood water. Thus، the results showed significant (at 1% level) reduction in EC and significant (at 5% level) decrease in pH in areas with flood water distribution، but there was no significant difference in lime content of sub surface soil.

Heating affects soil physical and chemical properties and sometimes causes soil water repellency. In order to investigate heating effect on water retention curve، an organic soil was heated in a muffle furnace preheated at 100 (T100)، 200 (T200)، 300 (T300)، 400 (T400) and 500 °C (T500). Hence، the soil was exposed to five heating treatments in three replications، in a completely randomized design. Water repellency was determined by using water drop penetration time method and aqueous ethanol method. Water retention curve of the treatments was determined by means of sand box and pressure plate. The van Genuchten equation''s parameters were obtained by minimizing mean square procedure and using RETC software. Then، heating effects were determined using SAS8 and LSD model. Some properties of water retention curve in heated and unheated soils were measured. The results showed that the original soil had low water repellency، while، at 300 °C، strong water repellency appeared، but disappeared by increasing the temperature. Van Genuchten equation''s parameters changed by increasing temperature and water repellency. The hydrophobic soils had low saturation water content compared to the other treatments with similar texture. T500 had the least saturation water content، probably because higher temperature decreased organic matter and increased sand and ash content. The value of α in hydrophobic soil was lower than other treatments with the same texture، but the “n” parameter in hydrophobic soils was higher than that in T100 and T200 treatments. Since this parameter is lower in heavy soils than light soils، it was low in T400 and T500 with sandy loam texture compared with the other treatments with loam texture. Water content at field capacity and wilting point diminished by increasing temperature.

Gas diffusion ratio in the soil compared to its diffusion in the atmosphere (DP/D0) and air permeability in the soil (Ka) is a function of soil physical characteristic، including pore size، pore continuity، and air porosity. Also، gas diffusion in soil is different based on the shape، moisture content، size، and pore tortuosity. In this study، 30 soil samples from different textural classes were prepared as undisturbed soil using a steel cylinder. At different moisture contents، DP/D0 values were measured with oxygen diffusion unsteady method and Ka was measured using falling head method. Finally، DP/D0 and Ka changes at various soil moisture levels and regression equations showing their relation were obtained. The results indicated that with increasing soil moisture، DP/D0 and Ka decreased as logarithmic function such that the maximum values of these two properties were achieved at low soil moisture and their minimum values at near saturation moisture. The obtained R2 values for DP/D0 and Ka (0. 75 and 0. 58، respectively) showed that، assuming other soil physical properties remain constant، we could use these relationships to estimate DP/D0 from the amount of soil moisture with relatively good accuracy and considerable reliability، thus، by this method، the direct measurement of these two properties is not required.

Due to its continuation and extension in time and space، wind erosion has high destructive potential، especially in arid regions، and its damage to economic resources، especially soil and vegetation، is significant. Therefore، a comprehensive understanding of wind erosion formation، performance، affected areas، and overall effects is essential. The objective of the present study was to present a suitable method for providing wind erosion hazard zoning maps. At first، the role of six effective factors on wind erosion including height changes، geomorphology، stone sensitivity to erosion، soil types، diversity and density of vegetation cover and land use were studied according to the status of the study area. For this purpose، Numerical Taxonomy Method، a rating scale method، was used. In the context of this method، facies units were selected by geomorphological method. Then، erosion intensity and effective index were determined in every unit using Taxonomy Method. Finally، the zoning map was presented in GIS based on Arc View3. 2a. The results showed that sand dune units with plant coverage (SDPC)، bare clay grounds (BCG)، and clay grounds with plant coverage (CGPC)، with the greatest quantitative values of، respectively، 0. 76، 0. 76 and 0. 77 were prone to very intense wind erosion. In the meantime، the quantitative value of wind erosion risk for the entire region was estimated at 0. 52، which indicated high potential of the region for occurrence of wind erosion. Generally، based on the final layer، 15% of the area of Khezrabad basin is prone to high risk of very intense wind erosion and threatens70% of the region with intense wind erosion.

Infiltration is one of the most important parameters in irrigation and agriculture. Knowledge of soil infiltrability is needed for designing an efficient irrigation system. However، determination of soil infiltration variability، though it is a difficult task، is a prerequisite for any precision agriculture setup. In this study، spatial variability of infiltration at the regional scale (Shahrekord watershed) is investigated. A total of 111 infiltration curves، obtained by double ring method with constant water head، were used to scale the infiltration. Four theoretical models، namely، Green- Ampt، Kostiakov، Kostiakov-Lewis، and Philip’s were fitted to the data. Philip model was the best، based on Pearson correlation and MAE statistics. Transfer factor (A) and sorptivity (S) were spatially distributed in the watershed and were scaled by two different scaling factors of and، respectively. Afterwards، all 111 infiltration curves were scaled. Nugget effect and range of was 0. 0001 and 0. 793 km، which implies a high spatial correlation structure. Therefore، scaling by was superior to scaling by. Pearson correlation of 0. 944 and an error of 0. 426 between the measured and de-scaled data were determined.

In sustainable agricultural systems، soil biological potentials، such as useful and efficient soil microorganisms، have received especial attention. Non-symbiotic helpful bacteria in the plant rhizosphere، the so called plant growth promoting rhizobateria (PGPR)، directly and indirectly promote plant growth as well as quality and quantity of yield. One of the important stages in application of PGPRs is selection of efficient isolates. In the current study، in order to evaluate the efficiency of PGPR and Phosphate Solubilizing Bacteria inoculates on yield and chemical composition of corn، an experiment was conducted as factorial completely randomized block design in a field at Dashti region of Isfahan province. Treatments were: inoculation (one PGPR pseudomonas، two Phosphate Solubilizing Bacteria، and one un-inoculated control) and phosphorus fertilizer (0، 25%، 75%، and 100% of the recommended rate based on soil testing). At grains milk stage، maize plants from each plot were randomly selected and harvested، then، the grain yield as well as N، P، Zn، and Fe contents in plants were measured. The results indicated that the effect of inoculation on measured indices was significant (5% level) compared with the control. At all levels of applied fertilizer، inoculation increased corn yield compared with un-inoculated control. The highest grain yield was obtained by application of high levels of phosphorus fertilizer and PGPR inoculation. The two inoculated bio-fertilizer treatments had no significant differences in grain yield، seed weight، and number of grain in corn at different levels of the applied chemical fertilizer. But، there were significant differences in concentration of P، N، Fe، and Zn in corn plants.

In order to study variations of organic carbon، nitrogen، phosphorous، potassium، iron، zinc، copper، and manganese available in soil in response to different wheat based rotations، an experiment was conducted for 5 years with completely randomized block design، with 8 treatments and 3 replications. Treatments were: T1- continuous wheat culture، T2- wheat، wheat، wheat، canola، wheat، T3- wheat، sugar beet، wheat، sugar beet، wheat،T4- wheat، potato، wheat، potato، wheat، T5- wheat، potato، wheat، canola، wheat، T6- wheat، sugar beet، wheat، potato، wheat، T7- wheat، corn، wheat، potato، wheat، T8- wheat، corn، wheat، sugar beet، wheat. Results showed that the amount of macronutrients in surface soil layer varied with rotation and number of years. The %OC and the residual macronutrients and micronutrients were affected significantly in 5 years: %OC was reduced، the residual N increased، the residual P remained constant، and the residual K decreased in 5 years. Also، the residual Fe and Zn increased while the amount of residual Mn decreased، but the residual Cu remained unchanged in 5 years. The amount of %OC and the residual macronutrients and micronutrients were affected significantly by different rotations. T1 rotation had the highest levels of %OC and the amount of residual N، Fe، and Zn and the lowest level of residual K. T2 rotation، too، had the highest %OC and residual N، but the lowest level of residual P، Zn، and Fe and the highest level of residual Mn and Cu. T3 rotation had the highest level of residual P. T4 rotation resulted in the lowest level of %OC and residual N. T5 rotation had the highest level of %OC and the residual N and K. T7 rotation resulted in the lowest level of %OC and residual N. T8 rotation had the highest level of residual P.