مجله تحقیقات آب و خاک ایران
سال پنجاه و پنجم شماره 5 (پیاپی 101، امرداد 1403)

This research was carried out to determine the simultaneous optimal management of nitrogen (N) fertilizer and the time and duration of mid-season drainage (MSD) of rice from an environmental point of view. This experiment was conducted in three treatments: application of N fertilizer and then drainage 7 days later for 7 days (T1), drainage for 7 days and then application of N fertilizer (T2), and drainage for 10 days and then application of N fertilizer (T3). The control treatment included fertilization at the same time as T1 treatment and without mid-season drainage.The quality parameters of drain water were measured. The results indicated that the time of applying fertilizer and drainage has a direct effect on pH. The average EC during the growth period in T2 and T3 decreased by 46 and 73%, respectively, compared to T1. The trend of NH4+ changes was upward before MSD, but after MSD, it decreased by 23% in T1 and 54% on average in T2 and T3. The average concentration of NO3- in the end season in T1, T2, and T3 was 22, 36, and 69% lower, respectively, and PO43- was 29, 31, and 67% lower than in MSD. The statistical analysis showed that the effect of time and treatments on SAR, and Cl- was insignificant. Applying fertilizer after drainage for 10 days has lower negative impact on environment. Compating yield and component yield in treatments show that T2 (7 days mid drainage and then appling nitrogen fertilizer) is a more appropriate option.

In this study, the effect of biochar, leonardite and coal was investigated on humification and germination index, and the concentration of some elements in the co-composting of manure and forest organic materials. The experiment was conducted in a factorial design with two factors, namely treatments at two levels (2 and 4% by weight) mixed with the raw materials and time was the second factor. Sampling was carried out during the composting process in the first to 12 weeks, measuring temperature, EC, C/N ratio, nitrate, and total concentrations of P, K, Ca, Mg, Na, Fe, Zn, Cu, and Mn, humification and germination index in the compost. The results showed that the coal (2%) had the highest temperature, while the leonardite (2%) had the longest thermophilic phase period. The coal (4%) led to a significant increase in EC, and biochar increased nitrate concentration and C/N ratio. The addition of leonardite resulted in a significant increase in humic and fulvic acids concentrations, as well as the highest values of humification and of polymerization index. The additives did not have a significant effect on germination index and the E3/E5 and E4/E6 ratios. The control had higher concentrations of measured elements compared to other treatments. The results of this study suggest that considering the cost of raw materials, coal is a suitable treatment for accelerating the production and improving the quality of compost, and leonardite, due to its high humic substrate, can be used at the end of composting for the enrichment of the produced compost.

Examining the changes in the water quality parameters of the Karun River using satellite data and determining the modified quality indicators can be used to assess the vulnerability of irrigation water. In this research, the data of seven qualitative parameters: Na+, SAR, pH, Cl-, HCO3-, EC and TDS were used in six water measuring stations of Abbaspur, Ahvaz, Farsiat, Gotvand, Molasani and Soosan of the Karun River (1392-1398) and NSFWQI general water quality index was calculated. Correlation relationship and estimation errors were determined for two principal component reduction (PCA) and multivariate linear correlation methods. The results showed that multivariate correlation method is more suitable. The coefficient of determination for the seven water quality parameters was calculated as 0.44, 0.43, 0.03, 0.43, 0.09, 0.45 and 0.46 respectively, and for the NSFWQI index it was calculated as 0.46. The statistical correlation for pH and HCO3- is at a very low level; but for the other five parameters and the NSFWQI index, it is in average state. The significance level of estimation for Na+, SAR, Cl-, HCO3-, EC and TDS parameters is acceptable (P<0.001), and for pH is unacceptable (P<0.122). In general, there is an acceptable correlation between the bands extracted through the Landsat 8 satellite and most of the quality parameters of the Karun River, but necessary actions are proposed to improve the correlation relationships. Also, the NSFWQI index shows that the quality of water in the Karun River along the Khuzestan plain is not good enough.

In this study, the performance of a Proportional-Integral (PI) automatic control system for the operation of the main channel of the northern branch of the Abshar irrigation network was evaluated under low-water operation scenarios. The actions taken to achieve the research objectives included:1) Development of a hydraulic flow simulation model in the main channel of the Abshar irrigation network using a simplified Integral-Delay (ID) mathematical model. 2) Development of a decentralized PI automatic control operation model. 3) Coupling the automatic operation control model with the hydraulic simulation model in MATLAB and determining the proportional and integral coefficients of each controller using system identification methods. 4) Simulation of the operation status using the designed automatic system under normal, low-water, and severe low-water operation scenarios with input fluctuations. The simulation results demonstrated that the controller had acceptable capability in implementing desirable operation under normal operation scenarios, with performance evaluation indices MAE, IAE, and STE fluctuating within the ranges of 0.11 to 0.140, 0.0013 to 0.0182, and 0.0001 to 0.0011, respectively. With the emergence of low-water scenarios and their intensification, water distribution conditions were assessed as desirable in upstream intakes but uncertain in downstream intakes. The calculated maximum error values in the lower intervals ranged from -10 to -20 and -35 to -45 centimeters, respectively. The results showed that the controller transferred the effects of low-water conditions and inflow fluctuations downstream, resulting in desirable surface water distribution for upstream intakes but inappropriate distribution for downstream intakes.

Conversion of desert soils to cropland may cause changes in some soil properties. The objective of this study was to analyze the effects of converting desert soils to cropland (wheat) and orchard (pistachio) on the soil organic carbon (SOC) content and storage, particulate organic carbon in Abarkooh region (Yazd province). Three land uses included wheat, pistachio, and desert soils were assessed. In order to compare the soil properties in different land uses, In September 2018, soil samples from desert, wheat, and orchard sites were taken from 0–20 and 20–40 cm depths. From each depth, 10 composite soil samples were taken. After pretreatments of soil samples, the soil properties including electrical conductivity, pH, gravel, sand, silt, clay, bulk density, organic carbon, calcium carbonate, were measured according to standard protocols. According to the obtained results, bulk density, gravel content and electrical conductivity decreased after the cultivation of desert soils. The SOC contents in the croplands and orchard were about 3.4-5.8 times higher than those in the desert soils. Also, the results showed an increase of 5.7 to 15.8 times of soil particulate organic carbon in the wheat fields and pistachio orchards compared to desert soils. The lowest SOC storage was observed in desert soils (0.19-0.24 kg.m-2) and the highest was obtained in pistachio orchards (1.08-1.12 kg.m-2). According to the findings of this study, it seems that sustainable cultivation and irrigation of desert soils could be an appropriate method which considerably enhances soil organic carbon sequestration in the study area.

Iran, as an arid and semi-arid region, is facing with reduction of renewable water resources, and the demand for water continues to increase. This has forced the decision makers to preserve high quality water resources for drinking purposes and less quality water resources (including reclaimed wastewaters) to be allocated for irrigation of agricultural lands. However, the accumulation of heavy metals in crops irrigated with reclaimed wastewater is still unclear. Therefore, the concentration of these metals in plants should be measured and monitored, regularly due to their risk of diseases. In this research, the effects of irrigation with municipal reclaimed wastewater on the accumulation of heavy metals in the roots and aerial parts of coriander plant were investigated and compared to well water (control). Results showed that the concentrations of proposed heavy metals in different parts of coriander plant irrigated with reclaimed wastewater were significantly higher than those in the control treatment. Fortunately, the concentrations of all these metals in all the plant tissues were lower than the permissible limits. The highest concentrations of copper and zinc (25 and 51 mg/kg, respectively) were observed in the aerial part of coriander. Therefore, in the current situation of the shortage of water resources in Kermanshah, reclaimed wastewater provides a unique and viable supply of water for the irrigation of large areas of coriander cultivation in such a way that it does not pose any threat to human health in terms of the accumulation of heavy metals in the plant.

Evapotranspiration (ET) plays a crucial role in arid and semi-arid regions, and its precise estimation of ET is essential for effective irrigation planning and management. Semnan province faces challenges due to a scarcity of synoptic and evaporation stations, making spatial estimation of ET difficult. This study utilized the evapotranspiration product from the ERA5-Land reanalysis dataset, in conjunction with auxiliary variables such as elevation and temperature, to estimate ET in the study area. The Random Forest (RF) model was employed to establish the relationship between auxiliary variables and ET data, resulting in the creation of an ET map using the RF model. The accuracy of the RF model in estimating ET was assessed against observational data using four statistical criteria: R², BIAS, RMSE, and KGE. The validation results demonstrated the high efficiency of the RF model (R² = 0.95, BIAS = -4.1, RMSE = 98.6, and KGE = 0.92). It was observed that the RF model's performance in ET estimation is influenced by the relationship between model error (BIAS) and topography, with elevation playing a significant role in ET estimation accuracy. This study underscores the effectiveness of utilizing data mining and processing techniques within the R programming environment to accurately estimate ET in regions with limited weather stations, particularly in arid and semi-arid areas. By leveraging these methods, it becomes possible to enhance the estimation of evapotranspiration in such challenging environments.

The fluctuations in the extent of the dry area have profound implications for the delta's ecology, sediment transport, and overall geomorphological development. This study aims to elucidate the effects of various factors, including storms and cold fronts, as well as river discharge, on the dry area of the Wax Lake Delta (WLD), US. Utilizing the Delft3D hydrodynamic model, a series of simulations covering from August to September 2021 was performed to quantify these influences. The model was calibrated and validated using measured water level data, ensuring the reliability of the simulations. Results indicate that the average dry area of the WLD for September 2021 is approximately 25.1 km², which largely depends on meteorological forces and river discharge. Specifically, extreme storms have the potential to submerge the delta, resulting in prolonged periods of inundation. Moreover, the passage of a cold front can lead to a submersion of up to 48% of the delta's area during the pre-frontal phase, followed by an 80% increase in the dry area in the subsequent post-frontal phase, illustrating the transient but significant impact of such events. The study also determines that river discharge has an inverse relationship with the dry area of the delta; an increase in discharge corresponds to a decrease in the dry area, and conversely, a decrease in discharge leads to an expansion of the dry area. The insights gained from this research underscore the importance of integrating meteorological and hydrological data in the management and conservation strategies of deltaic environments.

Mining activities provide a pathway for the entry and accumulation of heavy metals in soil. Utilization of biochars could remediate such contaminated soils. Therefore, in this study, the impact two percent of different wastes and biochars (prepared at temperature of 600 °C) was investigated on the availability and release kinetics of lead in polluted soil. Sandy loam calcareous soil, which was collected near Bama lead and zinc mine located in Sepahan Shahr city, was treated with residues and biochars and incubated for 120 days. Then the availability and release kinetics of lead were measured in control and treatments extracting with diethylenetriaminepentaacetic acid solutions (DTPA-TEA) during 504 hours. Results showed that treating soils with biochars, decreased the bioavailablaty and release kinetics of Pb significantly in comparison with control. The comparison of the coefficient of explanation (R2) and the standard error of estimation (SEE) of equations showed that simple Elovich equations, power function and first order equations had the highest coefficient of explanation and the lowest standard error of estimate for control and treated soils. So, these mathematical equations have been useful in explaining the cumulative release and release rate of Pb. Values of 1/β (derived from the simplified Elovich equation) and b (derived from the power function equation) changed from 161.47 – 237.18 mg kg-1 h-1 and 0.245 – 0.299 mg kg-1 h-1, respectively. Correlation analysis study, between DTPA-Pb with constants illustrated that among the constants, “K1”, “1/β”, “b”, and “a*b” were better parameters to predict the release kinetics of Pb.

Cover plants, among the most commonly used plants in the realm of green spaces, are typically characterized by shallow roots. In this research, a simple and flexible algorithm has been introduced for calculating the basal crop coefficient and evaporation coefficient of shallow-rooted plants without the use of (micro-) lysimeters. The presented algorithm requires measurements of moisture at three depths for short-term calculations and only surface layer moisture monitoring for long-term calculations. Using this algorithm, it is possible to calculate the potential evaporation and transpiration of the plant. Furthermore, the presented algorithm is independent of time steps. To evaluate this algorithm, nine experimental plots were utilized, including six Frankenia plots with full coverage and three bare soil plots during the peak water demand period. All experiments were conducted at the educational site of irrigation systems in the vicinity of the meteorological site of Ferdowsi University of Mashhad (FUM). For this purpose, the water content and irrigation of these plots was fulfilled (at most) every 48 hr. The results indicated that the presented algorithm has good capabilities for estimating the basal crop and evaporation coefficients. Additionally, the basal crop coefficient for Frankenia plant was found to be 1, and the evaporation coefficient was 0.58. Therefore, this method can be employed for estimating the water requirements of different plants without using (micro-) lysimeters.