حسین عسگرزاده

The present study was conducted to investigate the impact of organic (vermicompost and biochar) and chemical (gypsum and elemental sulfur) amendments and combination of vermicompost and chemical treatments on salinity, sodicity, and biological characteristics of a saline-sodic soil. This study was performed as factorial with two factors (with and without microbial inoculation) based on a completely randomized design with three replications in greenhouse conditions. After mixing with different treatments, soil samples were kept in the field capacity for 120 days, and wheat was cultured for 150 days following leaching soil samples. The most important chemical and biological properties of all soils were determined after harvesting the wheat plants. The results showed that the effect of each of the main factors of chemical and organic treatments including microbial inoculation and without microbial inoculation significantly (at the level of 5, and 1%, respectively) decreased the pH, EC, and ESP, the interactions of the factors did not have a significant impact on reducing them. For both factors, the role of combined treatments in improving the above indices was significantly greater than individual treatments. The main effect of experimental factors significantly affected (p <0.01) most biological indicators including basal respiration, substrate induced respiration, and soil microbial biomass carbon. However, the interactions of the factors significantly affected only microbial biomass carbon (p <0.05). Among all the treatments of both factors, the combined treatment of vermicompost and gypsum had the greatest effect on all three soil biological indices. This suggests that this treatment may have improved the soil ecosystem to increase and improve the activities of microorganisms by better improving soil chemical conditions than other treatments (such as reducing soil salinity and pH), and providing a substrate with more degradable carbon storage.

This study was conducted in the summer of 2021 to evaluate and validate the gravimetric soil water content measurements using a field oven. Ten soil types with a salinity of saturated paste (ECe) less than 4 dS m-1 and three saline soils were studied around Urmia Lake. Plots with dimensions of 1 m × 2 m were prepared for the selected soils to measure gravimetric soil water content and soil physical and chemical properties. The gravimetric water content (θm) values measured using the field oven (i.e., θmFO), were compared with those measured by a standard lab oven (i.e., θmLO). The soil water content values measured in the lab, regarded as a benchmark, were measured at 105 °C for 24 h. Temperatures of 120, 140, and 160 °C with three durations of 10, 15, and 20 min were used to dry the soil samples in the field oven. There was very good compatibility between the values of θmFO and θmLO when the soil samples were dried in the field oven for 15 or 20 min at all three temperatures. Significant linear relations were obtained between the θmFO and θmLO values as the slopes of linear relations were close to 1, the intercepts of relations were negligible and the distributions of measured data around the line 1 to 1 were unbiased. The minimal effects of soil organic matter content, clay content, salinity, and bulk density on water content measurements by the field oven indicate an important advantage of this method. These results confirm the high efficiency of the field oven for fast and reliable measurements of water content in different soils.

Soil salinity has a negative effect on physical, chemical and biological properties of soil. Salinity also affects the relationships between soil and plants, which in turn has a significant effect on plant growth. One of the solutions used to reduce the effects of salinity and improve the physical properties of the soil is application of organic and chemical conditioners. Organic matter as well as calcium improve the structure and physical condition of the soil. Conditioners in saline soils include soluble calcium salts such as gypsum (CaSO4.2H2O), calcium chloride (CaCl2.2H2O) and phosphogypsum (phosphorous gypsum), and acids such as sulfuric acid, sulfur, pyrite, Aluminum sulfate and sulfur lime (calcium polysulfide). Strategies aimed at evaluating and ameliorating the structural quality of soils should be developed to ensure the sustainable use of lands. The least limiting water range (LLWR) attempts to incorporate crop-limiting values of soil strength, aeration, and water supply to plant roots into one effective parameter (on the basis of soil water content). The LLWR can be a useful indicator of soil quality and soil physical constraints on crop production. Therefore, the objective of this research was to study the effects of organic and inorganic conditioners on some structural and hydraulic indices of saline sodic soils.

In this study, the effect of two types of organic and chemical conditioners and the simultaneous application of them on modifying the physical properties of 5 saline soils around the lake of Urmia were investigated. Treatments included algae, salfit and algae+salfit. The soil samples were transferred to culture boxes (40 × 40 × 40) according to the bulk density of the sampling site. The soil samples were wetted and dried several times. Conditioners treatments including application of calcium and organic compounds. After reaching the field capacity, wheat seeds were sown and irrigated with water (electrical conductivity 0.28 dS/m and pH= 7.78). It should be noted that irrigation was done at intervals of 8 days. Two months after the beginning the experiment, irrigation was stopped and soil moisture was allowed to reach a permanent wilting point. At this stage, undisturbed soil samples were prepared from the treated soil of each box and the mean weight‐diameter of dry (MWDdry) and wet (MWDwet) aggregates were measured. Then the values of least limiting water range in two suctions of 330 and 100 cm and water integral capacity of samples were measured.

According to the initial analysis, all soils used were saline and the amount of calcium carbonate was high in two soils (number 3 and 5). Soil organic carbon content was also low. The results of salfit analysis also showed that the dissolved calcium and sulfur content were 8 and 3.9%, respectively. The results showed that soil 1 had the highest amount of MWDwet and soil 5 had the lowest amount of MWDwet. The highest and lowest aggregate stability values were obtained in soils 3 and 5, respectively, where soil 5 was very saline soil. The studied soils differed in terms of soil water relations. The highest amount of LLWR330 was found in soil 5, while the lowest amount of LLWR100 and IWC parameters was also obtained in same soil. The results of this study showed that salfit treatment caused the highest increase in aggregate stability (74.9%) LLWR330 (14.5%) and integral water capacity (26.2%) compared to the control and the highest mean weight‐diameter of aggregates in both wet and dry conditions was obtained in salfit-algae treatment (52.4% and 40.4% increase, respectively). The results of correlation analysis among the measured parameters showed that the highest correlation was found between aggregate stability and MWDwet. Among the measured parameters, aggregate stability had the highest correlation with other parameters and the correlation of this parameter with LLWR330, LLWR100, IWC and MWDwet were 0.36, 55, 75 and 88 %, respectively. Soil water integral capacity also had a significant correlation (p < 0.01) with LLWR330 (0.84) and MWDwet (0.7).

The effect of initial soil properties on studied parameters was significant and the use of conditioners improved studied parameters, and use of conditioners increased indices structural and hydraulic of saline soils. In general, the results of this study showed the positive effect of conditioners on physical properties of the studied soils, in which salfit and salfit-algae have a better effect on studied parameter, and they could be useful to improve soil physical condition. It seems that the application of different rates of conditioners as well as their interaction with each other should be considered according to the basic properties of the soil.

This study was conducted to evaluate the soil physical quality (SPQ) indices of topsoil and subsoil of wheat and sunflower fields in Urmia plain. Principal component analysis (PCA) was used to distinguish the effect of soil layer and cultivation type on SPQ. Soil samplings and measurements were done in two layers (topsoil and subsoil) of 30 agricultural fields (15 wheat fields and 15 sunflower fields). Soil water retention and penetration resistance curves of undisturbed samples were determined using sand box and pressure plate, and micro-penetrometer, respectively. Then, least limiting water range (LLWR), integral water capacity (IWC), and Dexter’s index of soil physical quality (S-value) were calculated. There were significant differences (p < /em><0.05) in the mean values of physical quality indices between the topsoil and subsoil. The relative bulk density (RBD) values of subsoil were bigger than topsoil. Also, the IWC, LLWR, and S values of subsoil were much smaller than those of topsoil, indicating poor physical quality of subsoil layer in the studied fields. This might be related to conventional tillage with heavy machinery, especially under high soil moisture conditions in last decades, which induced some compaction effects in the subsoil. These findings recommend improving of tillage systems and continuous monitoring of cultivation effects on SPQ in the studied area. Evaluating the SPQ indices of wheat and sunflower fields, using the means comparison and PCA, showed that wheat fields had better soil physical quality compared to sunflower fields. The difference of root systems and more human trafficking in the sunflower fields could be the main reasons of lower soil physical quality in sunflower cultivation compared to wheat cultivation.

The aim of this study was to determine the critical limits and optimal range of relative bulk density (RBD) obtained using proctor test (RBDProctor) and axial stress of 200 kPa (RBD200kPa) for a silty clay loam soil which were determined based on relative grain yield, relative shoot dry, relative height and relative root volume of sunflower (Helianthus annuus L.). The relative values were obtained by dividing the absolute mean values of mentioned traits to observed maximum values of each trait. A range of soil bulk density (1.35 to 1.59 Mg m-3) was prepared in 10 bins (40 cm × 50 cm with 50 cm depth) using rollers of different weights. The bins were located out-doors after sowing sunflower and the weight of bins and drained water volume were measured daily. The soil water content was retained in the range of field capacity (FC) to 0.6FC through irrigation. The optimal ranges of RBDProctor and RBD200kPa were assumed to be the ranges in which the relative traits of sunflower were greater or equal to 0.95 of maximum value predicted by obtained equations fitted to relative data versus RBD. Sunflower yield was maximum at RBDProctor equal to 0.854 and the optimal range of RBDProctor based on relative grain yield was from 0.823 to 0.884. In this range sunflower relative grain yield was greater or equal to 95%. The corresponding values of RBD200kPa were 0.975, 0.940 to 1.009, respectively. This finding revealed that at the RBD values less than lower limit and greater than upper limit of starting restriction, unsuitable physical conditions reduce sunflower relative grain yield.

Empirical and theoretical methods (energy balance) are widely used to calculate the Crop Water Stress Index (CWSI) and irrigation scheduling to describe crop water status. In this study, irrigation scheduling was performed at the research farm of College of Agriculture, Urmia University, using a manual infrared thermometer and the empirical method of Idso et al. (1981) for the black gram under different irrigation regimes using drip irrigation in 2017. The experimental design was carried out in a randomized complete block design with three levels of irrigation I1, I2 and I3 which were 50, 75 and 100 percent water requirement in three replications, respectively. Using the baselines obtained for each treatment, the average CWSI values during the growth season of black gram for I1, I2 and I3 treatments were calculated to be 0.37, 0.23 and 0.15 respectively. The relationship between CWSI and total irrigation depth (mm) was determined as CWSI = -0.0008 (I) + 0.58, and the relationship between black gram grain yield (ton/hec) and CWSI was determined as Yield = -1.8237 (CWSI) + 2.1435 which their correlation coefficients (R2) were 0.98 and 0.99 respectively, which shows the high accuracy of regression models. In general, if the amount of water decreases with stress during the plant growth, the CWSI value increases, and as a result of increasing CWSI, the crop grain yield decreases. Finally, the no stress treatment (I3) with CWSI=0.15 was the basis for irrigation scheduling and then some relationships were established for determining the irrigation time using CWSI in Urmia climate for four stages of black gram growth; flowral induction-flowering, pod formation, seed and pod filling, and physiological maturity as (Tc  ̶ Ta)C = 1.9498  ̶ 0.1579(AVPD), (Tc  ̶ Ta)C = 4.4395 ̶ 0.1585(AVPD), (Tc  ̶ Ta)C = 2.4676  ̶ 0.0578(AVPD) and (Tc  ̶ Ta)C = 5.7532  ̶  0.1462(AVPD), respectively.

Infrared thermometer is one of the proper irrigation scheduling tools that can be used in fields or gardens with different soil texture. In order to schedule irrigation of maize (SC704) in Urmia climate conditions, using a difference in temperature of canopy cover of plant and air in 2017, a research was conducted at research farm of Urmia University college of agriculture under drip irrigation. In this research, the effects of various irrigation water treatments were investigated. The experimental design was carried out in a randomized complete block design with three levels of irrigation I1, I2 and I3 of 50, 75 and 100 percent of water requirement in three replications, respectively. Based on the results, the average values of CWSI for maize during the growth period for treatments of I1, I2 and I3 were calculated to be 0.53, 0.44 and 0.28, respectively. The results showed that the CWSI index increased with decreasing water requirement. The threshold of water stress index (0.28) of I3 treatment (no stress treatment) was the basis for irrigation scheduling. Then, some relationships were presented to determine the irrigation time of maize, using the CWSI index in Urmia climate for July, August and September as ,and  respectively.

Soil structural properties which are influenced by pore size distribution are important physical indicators of soil that affect plant and root growth. Irrigation water quality by affecting salt concentration and sodicity of soil solution alters the soil structure. This study was carried out to investigate the effects of different water qualities on pore size distribution, aeration porosity, soil water characteristic and mechanical resistance curves of a clay loam soil, irrigated with different water qualities. A combination of three levels of EC (1, 6 and 10 dS m-1) and SAR (1, 5 and 12 (meq L-1) 0. 5) values were used to simulate the different types of irrigation water. The undisturbed soil samples (45 mm length and 51 mm inner diameter) were treated with solutions for 5 cycles of saturation and drying. The result showed that at each SAR, as water EC increased, the salinity enhanced the soil macroporosity and aeration porosity as a result of flocculation that is effective in development of stable structure. Due to increasing the micoporosity and water holding capacity, the amount of retained water in filed capacity was increased. Saturated water content was increased due to the effects of salinity on pore alteration, as a result of contraction of diffuse double layer and particle’s flocculation. It is also seen that penetration resistance decreased probably due to development of macro pore. At each EC level, as the sodicity of irrigation water (SAR) increased, the moisture content at field capacity and retained water were increased due to structural disruption, clay swelling and dispersion which lead to increased adsorptive and interlayer surfaces. It was also observed increasing in miroporosity and penetration resistance and decreasing in macroporosity and aeration porosity with increasing SAR.

The range of soil water content where plant growth is least limited by water potential, soil aeration or mechanical resistance is called least limiting water range (LLWR). This study evaluated the values of LLWR determined according to the procedures proposed by da Silva et al. with those calculated on the basis of sunflower plant (Helianthus annuus L) response (LLWRP). In both methods LLWR is taken as the difference between the two soil moisture limits designated as upper (θUL) and lower (θLL). In the first method, the two limits are determined basically from the soil moisture and soil resistance characteristic curves, almost overlooking the plant type and its particular needs or behaviors. In the second method, as proposed in this research, the two limits are determined based on the stomatal response in a sandy clay loam soil packed into PVC tubes (called pots hereafter) with 30 cm diameter and 70 cm height at three compaction levels (soil bulk density equal to 1.75, 1.55 and 1.35 Mg.m-3) designated as D1, D2 and D3. Each pot was planted with three pre-soaked sunflower seeds and pots were kept under optimum condition until onset of the flowering stage. At this time two successive drying cycles were imposed and soil moisture and midday stomatal conductance were routinely measured. LLWRP were computed on the basis of relationship between soil matric suction and stomatal conductance. Results showed that on the basis of stomatal conductance behavior water uptake began at the soil matric suctions of 44, 16, 60 and continued up to 17394,31614, 39983 cm in D1, D2 and D3 treatments, respectively. Appreciable differences were observed between LLWR and LLWRP particularly when the lower limit moisture suction (equivalent to θUL for LLWR) was set at 330 cm (LLWR330). LLWR330 values of 0.148, 0.147 and 0.080 cm3cm-3 were obtained for D1, D2, D3 treatments, respectively, which were 51, 49 and 63 percent lower than the corresponding LLWRP values. This differences imply that the two moisture limits (θUL and θLL) proposed by da Silva et al. may not be applied indiscriminately for all plants and thus need to be modified according to plant needs or responses.

Integral water capacity (IWC) is the integral of differential water capacity functions in the range of 0 to infinity soil matric potential multiplied [H1] by weighting functions each taking into account the effect of varioussoil limitations that may develop at a given soil matric potential domain and restrict soil water availability to plant roots. The domains selected for development of weighting functions in most studies have seldom been based on plant response, but rather arbitrary. The purpose of this study was implementing midday green leaf temperature (TL) as a plant-response-based variable to compute integral water capacity. For this purpose, a sandy clay loam soil passed through 4.76 mm sieve was evenly compacted to three bulk densities of D1=1.35, D2=1.55, and D3=1.75 g cm-3, each replicated thrice, in PVC tubes (called pots hereafter) with 30 cm diameter and 70 cm height. Sunflower (Helianthus Annuus L) seedlings were planted in the pots and, after their full establishment, two periods of wetting and drying cycles were imposed. By monitoring daily soil moisture content at the three depths in the pots and converting them to soil moisture suctions along with the midday TL measurements, a plant-response-based weighting function was developed and integral water capacity (IWCP) was computed. Integral water capacity (designated as IWCG) was also computed by adopting the weighting functions proposed by Groenevelt et al. IWCP and IWCG in D1 treatment were obtained as 0.187 and 0.229 cm3cm-3, respectively. At the highly compacted D3 treatment, the corresponding values diminished to 0.152 and .038, respectively, equivalent to 19% and 84% reduction in soil water availability and reflecting the dominant effect of soil compaction on water availability. Averaged over the three compaction levels, IWCP and IWCG were 0.169 and 0.14 cm3cm-3,indicating that water availability determined on the plant response basis was 17% greater than that predicted by IWCG. This difference and over-susceptibility (84%) of IWCG to soil compaction imply that the soil suction domains proposed for the various soil limitations and the experimental relations employed in Groenevelt et al. approach to quantify their restricting effects as weighing functions need to be modified according to each particular plant needs or response.

This study was conducted to investigate the role of rock fragment content on water retention and soil penetration resistance curves as well as determining the correlation of soil physical quality indices with therock fragment content of the soil.A silt loam soil, containing 5% w/w 2 to 5 mm in diameter rock fragments, was used for this study. Experiment was carried out based on completely randomized design atsix treatmentsand three replications. The treatments including six levels of 5, 10, 15, 20, 25, and 30% w/w 2 to 5 mm in diameter gravel. Large drainable soil bins (40 cm × 50 cm with 50 cm depth) were used in this study. The bins were put outside (under natural conditions) after sowing of wheat (Triticum aestivumL.) and received enough amounts of water using irrigation and rainfall.There were significant differences (p

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.

Air filled porosity as one of the most important properties of the soil, can influence the availability of water, oxygen, and other nutrient elements. In order to investigate the interactions between air filled porosity levels and urea and phosphorus fertilizers it was done on availability of macro elements (N-NO3, P, K). A factorial experiment was carried out based on the randomized completely design with two factors including air filled porosity at seven levels (0, 4, 8, 12, 16, 20, 24%), and fertilizer at two levels (control and optimum level) from mono calcium phosphates and urea sources in the incubation period in three times (40, 80, 120 days) at three replications. Some of the chemical characteristics of treated soils such as pH, concentration of bicarbonate (HCO-3) and nitrate ions, and available phosphorus and potassium at different levels of air filled porosity were measured. Results showed that the correlation between pH, nitrate, bicarbonate, phosphorus and potassium with air filled porosity changes was significant. Increasing the incubation time was caused to reduce the amount of availability nitrate, phosphorus and potassium soil. Also with decreasing air filled porosity levels pH, HCO-3 concentration and availability of phosphorus were increased. The concentration of nitrate ions under the influence of temperature, pH, moisture and oxygen in different of the air porosity levels (12, 16 and 20%) showed a significant increase. So the air filled porosity of 12, 16 and 20 percent were determined the optimal range for the concentration of nitrate, phosphorus and potassium available

Field saturated hydraulic conductivity (Kfs) is one of the most important soil properties that considerably contribute to soil quality. However, specifically in the structured soils, the measurement of Kfs is difficult and time-consuming. Therefore, verifying the simple and fast methods for Kfs measurement is needed for effective soil monitoring. This study was conducted to investigate the effect of ring size (rings with diameters of 5.5, 10.88, 16, and 31.8 cm) on the Kfs measured with simplified falling head (SFH) single ring method in a structured clay loam soil. Furthermore, the effect of conventional tillage on Kfs was assessed and the Kfs measured with double ring (DR) method and SFH procedure was compared. Results showed that while the ring size affected the measured Kfs, the discrepancy between Kfs results of given ring size compared to the smallest ring size (d = 5.5 cm) was practically negligible (factor of discrepancy ≤ 0.27). The effect of tillage operations on the measured Kfs was substantial (discrepancy between Kfs results of 2.1 to 3.1). The SFH and DR techniques yielded statistically different means of Kfs. However, the discrepancy between the Kfs values obtained with the SFH method using the largest ring size and the Kfs values determined with DR method was practically negligible (factor of discrepancy

A laboratory method was proposed and its capability was evaluated for quick and reliable determination of soil available water (SAW) for plant using concepts of plant available water (PAW), least limiting water range (LLWR) and integral water capacity (IWC). Water retention (θ) of 20 agricultural soils was detemined at 13 matric suctions (h) using sand box and pressure plate apparatuses. These data were fitted by the van Genuchten model and considered as the reference method. We used the soil water retention at h values of 0, 330 and 15000 hPa for the model fitting in the proposed method. Penetration resistance (Q) was measured on 10 undisturbed cores at different water contents for each soil using a lab micropenetrometer. Except for PAW (with h of 100 hPa considered as field capacity), there were not significant differences between the mean values of SAW determined by the reference and proposed methods. Strong regression lines were obtained between corresponding SAW values calculated by the two methods. Therefore, it is not needed to measure soil water retention and penetration resistance curves at several h values; instead water retention measurement at h values of 0, 330 and 15000 cm and quick measurement of penetration resistance at different water contents could be used for determination of different quantities for SAW. The PAW, LLWR and IWC were negatively and significantly regressed with relative bulk density (RBD) in the studied soils. These findings show that the SAW values calculated by the proposed method are susceptible to soil structure and might be considered as soil physical quality indices. The results showed suitability of the proposed method for quick and reliable determination of soil available water quantities which are useful for applied purposes and irrigation scheduling.