Research Article
Irrigation
R. Saeidi
Abstract
IntroductionSalinity stress causes reduction of crop evapotranspiration (ETc) and yield. An unsuitable seed planting date can result in negative atmospheric effects, such as temperature stress, during the crop growth period. Consequently, salinity stress and unfavorable climatic conditions during this ...
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IntroductionSalinity stress causes reduction of crop evapotranspiration (ETc) and yield. An unsuitable seed planting date can result in negative atmospheric effects, such as temperature stress, during the crop growth period. Consequently, salinity stress and unfavorable climatic conditions during this period interact to reduce crop water uptake. The mentioned conditions effect, should be investigated on crop transpiration amount (actual water requirement) and soil surface evaporation losses. This research results will have a determinative effect on the optimal use of water resources. Materials and MethodsThe studied crop in this research was S.C 704 maize. The crop planting was conducted in mini-lysimeters with a diameter of 40 cm and a height of 70 cm. The experiment factors included soil salinity stress and seed planting date. Soil salinity treatments were selected at four levels of 1.7 (S1), 2.5 (S2), 3.8 (S3), 5.9 (S4) dS.m-1. Seed planting date included of 5 May (P1), 25 May (P2) 14 June (P3) and 4 July (P4). Crop growth period for all planting date treatments, was 140 days (FAO-56). Experiment was conducted as factorial based on completely randomized design with 16 treatments and three repetitions. Variance analysis and average comparison of data was done by SPSS software and with Duncan's multi-range test (at 5% probability level). Daily soil moisture amount was measured by a moisture meter. Irrigation time was determined for without water stress conditions. Readily available water limit was determined 0.4. Irrigation volume was calculated according to soil moisture deficit (up to FC limit), soil density, root depth, leaching fraction and soil surface area. To separate the evapotranspiration components, all treatments were performed in two series of mini-lysimeters. In the first series, soil moisture reduction was related to crop evapotranspiration amount. But in the second series, the plastic mulch was placed on soil surface. Soil moisture reduction in the second series, was only related to crop transpiration amount. Difference of data in the first and second series was equal to the evaporation amount. Linear function of Mass and Hoffman (1977) was used as the function of evapotranspiration-salinity, transpiration-salinity, and evaporation-salinity. Results and DiscussionAs salinity increased from S1 to S4 levels, evapotranspiration, transpiration, and evaporation amounts were measured on the planting dates P1, P2, P3, and P4. The measurements were as follows:Evapotranspiration (mm): 619-548 (P1), 621-549 (P2), 624-547 (P3), and 625-544 (P4)Transpiration (mm): 429-309 (P1), 421-295 (P2), 418-281 (P3), and 412-265 (P4)Evaporation (mm): 190-239 (P1), 200-254 (P2), 206-266 (P3), and 213-279 (P4)These ranges reflect the measured amounts for each variable under increasing salinity levels across the different planting dates. Under the influence of salinity stress, soil water potential decreases, leading to a reduction in water uptake by the crop and subsequently decreased crop transpiration. As a result of this reduction in crop water uptake, the remaining water in the soil is utilized for evaporation. In S4 level and on dates of: P1, P2, P3 and P4, crop transpiration portion decreased to 12.9%, 14.1%, 15.6% and 17.2%, respectively, and evaporation portion increased to the same amount. By adjusting the seed planting date to optimize the utilization of favorable atmospheric conditions during crop growth stages, the increase in the portion of evaporation is prevented. In initial stage of growth period, only 0 to 10% of soil surface is covered by crops (FAO-56) causing the evaporation component to have a dominant portion in the crop evapotranspiration parameter. As a result, placing of initial growth stage in warm days of year caused an increase in evaporation losses. It seems that S1P1 treatment was the optimal condition for transpiration increase and evaporation decrease. The estimated functions showed that (in salinity stress conditions) crop transpiration decreased more than ETc. Therefore, the transpiration rate should be considered as the crop's net water requirement instead of ETc (crop evapotranspiration). According to the Mass-Hoffman function, under stress conditions, the decreasing slope of transpiration and evapotranspiration and the increasing slope of evaporation become more pronounced. For instance, in planting dates of P1, P2, P3, and P4, for each unit (dS.m-1) of increase in soil salinity, the evapotranspiration rates decreased by 2.51%, 2.82%, 3.3%, and 3.65%, respectively. Similarly, the transpiration rates decreased by 6.1%, 7.34%, 8.42%, and 9.2%, respectively, while the evaporation rates increased by 5.5%, 6.7%, 7%, and 7.82%. ConclusionSalinity and atmospheric temperature stresses had interaction effects on evapotranspiration and components rates. Postponing the seed planting date and not utilizing optimal weather conditions, especially during spring, can lead to damage to transpiration, which is a favorable aspect; however it is unfavorable in evaporation,. Therefore, in irrigated crops, it is advisable not to plant seeds during the warm months of the year, especially in July and August. Consequently, by controlling soil salinity and selecting the appropriate planting date, water can be optimally utilized.
Research Article
Irrigation
A. Kazemi Choolanak; F. Modaresi; A. Mosaedi
Abstract
IntroductionPredicting river flow is one of the most crucial aspects in water resources management. Improving forecasting methods can lead to a reduction in damages caused by hydrological phenomena. Studies indicate that artificial neural network models provide better predictions for river flow ...
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IntroductionPredicting river flow is one of the most crucial aspects in water resources management. Improving forecasting methods can lead to a reduction in damages caused by hydrological phenomena. Studies indicate that artificial neural network models provide better predictions for river flow compared to physical and conceptual models. However, since these models may not offer reliable performance in estimating unstable data, using preprocessing techniques is necessary to enhance the accuracy and performance of artificial neural networks in estimating hydrological time series with nonlinear relationships. One of these methods is wavelet transformation, which utilizes signal processing techniques. Materials and MethodsIn this study, to evaluate the efficiency of discrete and continuous wavelet types in the Wavelet-Artificial Neural Network (WANN) hybrid model for monthly flow prediction, a case study was conducted on the Kardeh Dam watershed in the northeast of Iran, serving as a water source for part of Mashhad city and irrigation downstream agricultural lands. Monthly streamflow estimates for the upstream sub-basin of the Kardeh Dam were obtained from the meteorological and hydrometric stations' monthly statistics over a 30-year period (1991-2020). The WANN model is a hybrid time series model where the output of the wavelet transform serves as a data preprocessing method entering an artificial neural network as the predictive model. The combination of wavelet analysis and artificial neural network implies using wavelet capabilities for feature extraction, followed by the neural network to learn patterns and predict data, potentially enhancing the models' performance by leveraging both methods. The 4-fold cross-validation method was employed for the artificial neural network model validation, where the model underwent validation and accuracy assessment four times, each time using 75% of the data for training and the remaining 25% for model validation. The final results were presented by averaging the validation and accuracy results obtained from each of the four model runs. To evaluate and compare the performance of the models used in this study, three evaluation indices, Nash-Sutcliffe Efficiency (NSE), Root Mean Square Error (RMSE), and Pearson correlation coefficient (R), were employed. Results and DiscussionThe analysis of meteorological and hydrometric data in this study revealed that monthly streamflow in two time steps, T-1 and T-2, were the most effective predictive variables. Each of the two runoff variables of the previous month (Qt-1) and the previous two months (Qt-2) were analyzed by each of the Haar and Fejer-Korovkin2 discrete wavelet transforms and the two continuous Symlet3 and Daubechies2 wavelets at three levels. The results of each level of decomposition was given as input to the ANN model. The presented results at each decomposition level indicated that hybrid models could accurately predict lower flows compared to the single ANN model, and the estimation of maximum values also significantly improved in the hybrid models. Among the wavelets used, Haar wavelets exhibited the weakest performance, and the less commonly employed Kf2 wavelet showed a moderate performance. Since the Haar and Fk2 wavelets, with their discrete structure, did not perform well in decomposing continuous monthly streamflow data, continuous wavelet models outperformed discrete wavelet models. The hybrid models, combining wavelet analysis and artificial neural networks, demonstrated up to an 11% improvement over the performance of the single neural network model. ConclusionStreamflow is a crucial element in the hydrological cycle, and predicting it is vital for purposes such as flood prediction and providing water for consumption. The objective of this research was to evaluate the performance of different types of discrete and continuous wavelet models at various decomposition levels in enhancing the efficiency of artificial neural network (ANN) models for streamflow prediction. Since climate and watershed characteristics can influence the nature of data fluctuations and, consequently, the results of the wavelet model decomposition, choosing an appropriate wavelet model is essential for obtaining the best results. Considering the existing variations in the results of different studies regarding the selection of the best wavelet type, it is suggested to use both continuous and discrete wavelet types in modeling to achieve the best predictions and select the optimal results. Given that a lower number of input variables in neural network models lead to higher accuracy in modeling results, it is recommended to perform decomposition at a two-level depth to reduce input components to the neural network model, thereby reducing the model execution time.
Research Article
z
E. Karamian; M. Navabian; M.H. Biglouei; M. Rabiee
Abstract
IntroductionMany agricultural lands in Guilan province of Iran, especially paddy fields, remain uncultivated in the second half of the year due to various reasons including heavy rainfall, low soil permeability (stickiness of soil particles) and inefficiency of the existing drains. Mole drainage as a ...
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IntroductionMany agricultural lands in Guilan province of Iran, especially paddy fields, remain uncultivated in the second half of the year due to various reasons including heavy rainfall, low soil permeability (stickiness of soil particles) and inefficiency of the existing drains. Mole drainage as a low-cost drainage method, proportion for rice cultivation conditions and easier to implement than pipe drainage, can be a suitable solution in the development of second cropping. Due to the oil content of 40% of the seed, the rapeseed plant is one of the valuable oil plants and has the ability to be cultivated as a second crop in paddy fields. Nitrogen plays a key role in the performance of plants and its deficiency causes limitations in plant production. Equipping paddy fields with mole drains along with the application of appropriate level of nitrogen fertilizer can increase the quantitative and qualitative yield of rapeseed as a second crop and contribute to the food security of the country. Therefore, the development of the cultivated area of rapeseed in paddy fields after rice harvesting in Rasht region, the study of the combined effect of mole drainage and different levels of nitrogen fertilizer on yield and yield components were the aims of this project. Materials and MethodsIn order to investigate the effects of mole drainage and nitrogen fertilizer on the yield and yield components of rapeseed as a second crop in Rasht rice fields, a factorial layout based on a randomized complete block design with three replications at the research field of the Faculty of Agricultural Sciences of Guilan University was implemented in the crop year of 2022-2023. The factors included mole drainage at three levels (without drainage, without gravel and with gravel) as D0, D1 and D2 respectively, and nitrogen fertilizer as urea source at two levels (180 and 240 kg ha-1) as N1 and N2 respectively. Rapeseed plant (Brassica napus) of Delgan cultivar was selected as the second crop after rice harvest. To carry out the experiment, at first the desired land was blocked and divided into plots, then the underground drains of mole were created without gravel and with gravel with a special blade in the desired plots. To drain the drainage from the mole drains, the polyca pipe was installed at the end of each mole tunnel, then the other side of polyca pipe was connected to the sub-pipe collection and finally led to the main surface drain. This experiment was conducted in 18 plots and each one was 9 × 6 meters. The distance between plots was 1.5 m, between replications was two meters, and the distance between plants was 15 and between rows was 25 cm. To avoid the effectiveness of drainage treatments from undrained treatments, undrained plots were considered at the end of the field. Before cultivation, basic chemical fertilizers, 200 kgha-1 of potassium from potassium sulfate source and 200 kgha-1 of phosphorus from ammonium phosphate source were applied. Nitrogen fertilizer from urea source was applied at the level of 180 and 240 kgha-1 in equal amount at three stages. Just before the harvest stage, to determine the traits of the number of seed in the pods of sub-branches, the number of seed per pod, the weight of seed in sub-branches, the weight of seed in the main branch and the weight of seed per plant, ten plants were randomly selected and harvested manually from the crown area. Also, to determine the seed yield, one square meter was randomly selected from each plot, taking into account the borders, and the bushes were manually harvested from the crown area. After the moisture content of the seeds reached the desired level, the seeds were separated from the pods and weighed using a laboratory scale with an accuracy of one thousandth of a gram, and the seed yield was calculated in kgha-1. SOXTEC SYSTEM HT 1043 Extraction Unit set was used to determine oil percentage and Kjeldahl set was used to determine seed protein. Statistical analysis of the data was done using SAS software (version 9.4) and comparison of means was done using the minimum significant difference test at 5% probability level. Excel software was used to draw the graphs. Results and DiscussionThe results of variance analysis of the data showed that the interaction effects of mole drainage and nitrogen fertilizer on the traits of seed weight in the main branches, seed weight in the plant and seed yield was significant at 5% probability level, so that the highest seed weight in the main branch with 0.733 seeds in the mole drainage with gravel with a nitrogen fertilizer level of 180 kgha-1 (D2×N1) treatment was obtained and the highest seed weight in the plant with 1.443 g in the mole drainage without gravel with a nitrogen fertilizer level of 240 kgha-1 (D1×N2) treatment was obtained. Also, the highest seed yield was obtained under 3579.48 kgha-1 in the treatment of mole drainage without gravel using 240 kgha-1 of fertilizer (D1×N2) which is compared to the treatment of without drainage and drainage with gravel with the same level of fertilizer 13.63 and 2.31 percentage was higher, respectively. In addition, rapeseed plant is more important in terms of oil percentage, no significant difference was observed between drainage and nitrogen fertilizer treatments in terms of average oil percentage. Therefore, the mole drainage treatment without gravel with a fertilizer level of 240 kgha-1 (D1×N2) is the most suitable option for rapeseed cultivation as the second crop after rice harvesting. ConclusionThe results of this study showed that mole drainage without gravel by improving soil ventilation conditions and preventing waterlogging of paddy fields along with the level of nitrogen fertilizer of 240 kgha-1 increased the yield of rapeseed compared to the condition of without drainage at the same level of nitrogen fertilizer. Therefore, rapeseed cultivation in vast paddy fields after rice harvesting can be recommended as a basic solution in order to increase the production of oilseeds and provide part of the country's oil consumption.
Research Article
Soil science
Z. Sohrabzadeh; Y. Kooch
Abstract
Introduction Shrub covers play a pivotal role in pasture ecosystems, exerting considerable influence on various biochemical processes that occur within the habitat and surface layers of the soil. Despite their significance, there is a scarcity of research exploring the impact of different ...
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Introduction Shrub covers play a pivotal role in pasture ecosystems, exerting considerable influence on various biochemical processes that occur within the habitat and surface layers of the soil. Despite their significance, there is a scarcity of research exploring the impact of different types of shrubs covers on soil properties within pasture ecosystems. Consequently, this present study was undertaken to address this gap in knowledge and investigate the effects of shrub cover on soil characteristics specifically within a semi-arid climate, which is known for its delicate and vulnerable habitats. Materials and MethodsThe implementation of this research involved the consideration of the mountainous region of Kiakola, Nowshahr city. The current investigation focused on assessing the impact of various shrubs, namely Carpinus orientalis Miller, Crataegus microphylla C. Koch, Berberis integerrima Bunge, Prunus spinosa L., and Rhamnus pallasii Fisch. and C. A. Mey, on specific soil properies within the mountainous area of Kiakla, Nowshahr city. To carry out this research, 15 sites were selected for each of the aforementioned shrub species. Soil samples were collected from under the canopy of these species, specifically at a depth of 0-10 cm and a surface area of 30 cm × 30 cm. A total of 75 soil samples were then taken to the laboratory for analysis. The samples were divided into two parts: one part underwent physical and chemical tests after air-drying and passing through a 2 mm sieve, while the other part was stored at 4 degrees Celsius for biological tests. The presence or absence of significant differences in soil properties related to the type of shrub cover under investigation was determined using a one-way analysis of variance test. Principal component analysis (PCA) was utilized to establish the relationship between different soil characteristics within the studied shrub covers. Results and DiscussionAccording to the findings of this investigation, alterations in the shrub species present in the examined pasture habitat resulted in modifications to the majority of soil quality properties. Nevertheless, no statistically significant disparity was observed in the quantity of soil organic matter. However, it is worth noting that the quantity of organic matter in the subsoil of Carpinus species exceeded that of the other examined shrubs. Carpinus and Crataegus shrubs were associated with the lowest values of bulk density, while the shrubs under investigation had no significant impact on soil particle density. Furthermore, the subsoil of the Carpinus shrub cover exhibited the highest values of soil porosity. In the studied area, the most stable soil aggregates were observed beneath the Carpinus and Rhamnus shrubs. The subsoil of Rhamnus and Carpinus shrubs exhibited the highest and lowest quantities of sand, respectively. Similarly, the subsoil of Carpinus and Rhamnus displayed the highest and lowest quantities of clay, respectively. The soil under Rhamnus displayed the highest ratio of CR and MCR indices, whereas the subsoil of Carpinus exhibited the lowest values of these indices. Fulvic and humic acids demonstrated the greatest values beneath the Carpinus, Crataegus, Berberis, Prunus, and Rhamnus shrubs, respectively, following a comparable pattern. Additionally, the subsoil of Carpinus exhibited the greatest quantity of microbial ratio, while the soil under Rhamnus displayed the lowest quantity of this characteristic. The outcomes of the principal component analysis (PCA) revealed that the quantity of organic matter, clay content, fulvic and humic acids, porosity, and stability of soil aggregate in the soil beneath Carpinus played a significant role in enhancing the soil microbial ratio of this shrub in comparison to the other shrubs. Conclusion The findings of this investigation validate the capability of Carpinus foliage to ensure the conservation of soil quality indicators on the hilly grasslands of northern Iran. Therefore, it is proposed that restoration efforts be conducted in the designated region and other areas with similar ecological conditions. Additionally, it is recommended that special attention be given to the implementation of Carpinus and other indigenous shrub species to protect soil integrity.
Research Article
Soil science
S. Naseri; Sh. Kiani; H.R. Motaghian
Abstract
IntroductionUrea is one of the nitrogen chemical fertilizers for vegetable production in soil. But it is seldom used in soilless cultures. Leafy vegetables such as Lettuce (Lactuca sativa L.) contain high levels of nitrate and attempts have been made to reduce the nitrate concentration in this crop for ...
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IntroductionUrea is one of the nitrogen chemical fertilizers for vegetable production in soil. But it is seldom used in soilless cultures. Leafy vegetables such as Lettuce (Lactuca sativa L.) contain high levels of nitrate and attempts have been made to reduce the nitrate concentration in this crop for human consumption. Using reduced forms of nitrogen, i.e. urea, is one of the applied strategies for reducing nitrate accumulation in lettuce. Little information is available concerning urea as a source of nitrogen for production of leafy vegetables such as lettuce in soilless culture. This experiment was conducted to investigate the effect of different ratios of urea:nitrate in nutrient solution on the growth indices, yield and nitrate accumulation of red French lettuce (Lactuca sativa L. cv. Lolla Rossa) in soilless culture. Materials and MethodsA hydroponic experiment using completely randomized design was carried out with seven ratios of urea:nitrate in nutrient solution and four replications in the research greenhouse of Shahrekord University. Urea:nitrate ratios in nutrient solution were: 0:100, 10:90, 20:80, 30:70, 40:60, 50:50 and 60:40. Lettuce seedlings were grown in 2 L plastic pots (one plant per pot) containing mixture of cocopeat + perlite at the ratio of 2:1 (v/v) and were manually fertigated with nutrient solutions on a daily basis. Four weeks after transplanting, lettuce plants were harvested and fresh weights of shoot and root were determined. Plant growth indices including of plant height, plant diameter, leaf length, leaf width, leaf number, leaf greenness index and leaf brix level were measured. After measuring the growth indices, the leaves were grouped separately according to leaf numbers 1-10=outer leaves, >11= inner leaves. The samples were dried in an oven at 60 °C and were ground. Nitrate concentrations in samples were determined calorimetrically using a spectrophotometer at a wavelength of 410 nm. Analysis of variance was performed using SAS software version 9.4. Means comparison was conducted using least significant difference test at 0.05 probability level. Results and DiscussionThe results indicated that application of different ratios of urea to nitrate in nutrient solution had not significant effect on the lettuce growth indices including of plant diameter, leaf length, leaf width, leaf number, leaf greenness index and leaf brix level in comparison with 0:100 of urea:nitrate ratio. Also, root and shoot fresh weights were not affected by urea:nitrate ratio in nutrient solution. The greatest quantity of shoot fresh weight (141 g per plant) was obtained with a 50:50 urea:nitrate ratio. However, this was not significantly different from the shoot fresh weight (125 g per plant) observed when urea was not included in the nutrient solution. Shoot nitrogen concentration (except for plants nourished with a 50:50 urea:nitrate ratio) was not affected by increasing the urea:nitrate ratio in the nutrient solution. The results revealed that application of urea in nutrient solution effectively provided the nitrogen requirement of lettuce. This indicates that lettuce plants can efficiently hydrolyze urea and use it efficiently as a nitrogen source. Application of urea in the nutrient solution led to significant decrease in the nitrate concentration of lettuce root (P< 0.05). Moreover, increasing urea:nitrate ratio in nutrient solution resulted in significant decrease of the nitrate concentration of outer leaves, inner leaves and all leaves of lettuce (P< 0.01). The highest and lowest nitrate concentration in inner, outer and all leaves of lettuce were obtained in plants nourished with 0:100 and 50:50 urea:nitrate ratio in nutrient solution, respectively. Application of urea:nitrate ratio of 50:50 led to the meaningful decrease of nitrate concentration in root (43%), outer leaves (41%), inner leaves (44%) and all leaves (43%) of lettuce in comparison with 0:100 of urea:nitrate ratio. Urea had a repressive effect on nitrate influx and decreased its uptake by plants. Also, after urea uptake by plant root, it is first degraded by cytosolic ureases and then ammonium is incorporated via the GS-GOGAT (Glutamine Synthetase- Glutamine α-OxoGlutarate Amino Transferaze) cycle. Therefore, application of urea in nutrient solution can lead to the reduction of nitrate accumulation in plants. ConclusionBased on the shoot fresh weight and nitrate concentration in lettuce leaves, replacing 50% of nitrate in nutrient solution with urea is recommended for red French lettuce production in hydroponic culture under the conditions of the present study. Compared to other nitrogen fertilizers, urea has a lower price and its application in nutrient solution is useful in reducing production costs.
Research Article
Soil science
A. Barikloo; P. Alamdari; A. Golchin
Abstract
IntroductionHeavy metals such as lead, aluminum, mercury, copper, cadmium, nickel, and arsenic are now commonly found worldwide. Among these, cadmium and lead are the most hazardous, posing significant risks to both the environment and human health. Cleaning soils contaminated with organic and inorganic ...
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IntroductionHeavy metals such as lead, aluminum, mercury, copper, cadmium, nickel, and arsenic are now commonly found worldwide. Among these, cadmium and lead are the most hazardous, posing significant risks to both the environment and human health. Cleaning soils contaminated with organic and inorganic contaminants is one of the most significant and fundamental challenges facing society today. One effective method for soil purification is to extract or immobilize the contaminant within the soil. Materials and MethodsIt is unclear how water-soluble polymers contribute to the immobilization of heavy metals. The purpose of this study is to examine how various polymers affect the immobilization of lead, zinc, and cadmium in the soil near a lead and zinc mine in the province of Zanjan. A factorial experiment with three replications was conducted using a randomized complete block design. The experimental treatments included one type of soil and three different kinds of acrylic polymers (cationic, nonionic, and anionic) applied at four different levels (0, 0.05, 0.1, and 0.2). The absorbable amounts of lead, zinc, and cadmium were tested at various intervals after the polymers were applied to the soil samples. After that, SAS statistical software was used to examine the data. To do this, the Duncan multiple range test was used to compare the means. The necessary tables and graphs were then created using Excel. Results and DiscussionThe findings demonstrated that, at 1% probability level, the kind of polymer had a considerable impact on the amount of lead, zinc, and cadmium that may be absorbed in the soil. The average concentration of soil-absorbable lead for the different types of polymers employed was 239.8, 260.15, and 267.65 mg/kg; anionic polymer had the lowest concentration. Stated differently, anionic polymer decreases the capacity to absorb lead and stabilizes more lead in the soil than the other two forms of polymer. Anionic polymers most likely have a stronger impact on soil granulation. Additionally, at 1% probability level, the impact of acrylic polymer intake on the amount of lead, zinc, and cadmium absorbable in the soil was considerable. With an increase in the amount of polymer utilized in the soil, the greatest absorbable lead concentration (301.58 mg/kg) in the control treatment dropped to the lowest absorbable lead concentration (0.2). It was possible to determine the polymer percentage and the lead concentration, which came out to be 205.9 mg/kg of soil. Zinc concentration dropped as acrylic polymer consumption increased; in the control treatment, absorbable zinc concentrations ranged from 0.2 to 83.5 mg/kg of soil, with 0.2 being the highest concentration. At 1% probability level, the impact of the polymer's contact time with the soil on the amount of lead, zinc, and cadmium that the soil may absorb was significant. As a result, the tested soil had 414.52 mg of these elements at the initial stage of polymer treatment. The quantity of absorbable lead in the soil became 66% immobilized after a month, and after 720 hours, the amount of absorbable lead dropped to 141.83 mg/kg. As the polymer's contact time with the soil increased, so did the concentration of absorbable zinc in the soil. At 1% probability level, there was a strong correlation between the kind and amount of acrylic polymers and the amount of lead, zinc, and cadmium that may be absorbed in the soil. The ingestion of 0.2% anionic polymer resulted in the largest amount of lead immobilization, lowering the soil's absorbable lead concentration from 300 to 192 mg/kg of soil. A higher amount of anionic polymer immobilized the lead, and both cationic and non-ionic polymers were positioned after it. Additionally, anionic polymer was more prevalent than cationic polymer. It caused the non-ionic polymer's absorbable zinc to become immobile. Following 720 hours of polymer treatment, the soil's absorbable zinc element was immobilized to a greater extent by the anionic polymer (20%) than by the cationic and non-ionic polymers (26%), respectively. In comparison to the original concentration, the largest amount of immobilization by anionic polymer after one month was 78%, and the lowest amount of immobilization by nonionic polymer was 61%. Anionic polymer was 27% more effective than non-ionic polymer, 18% more effective than cationic polymer, and stabilized more cadmium. Conclusion The results of this study showed that with increasing the duration of contact of polymers used with the soil, the amount of mobility of heavy metals in the soil decreased and also with increasing the amount of polymer consumption, the rate of metal stabilization in the soil increased. Anionic polymers immobilize more lead, zinc and cadmium in soil. To reduce the mobility of lead, zinc and cadmium and improve the stability and increase aggregation in soil, the use of acrylic polymer in contaminated soil is recommended.
Research Article
Soil science
Sh. Asghari; M. Hasanpour Kashani; H. Shahab Arkhazloo
Abstract
IntroductionThe penetration resistance (PR) of the soil shows the mechanical resistance of the soil against the penetration of a conical or flat probe; it is important in terms of seed germination, root growth and tillage operations. In general, if the PR value of a soil exceeds 2.5 MPa, the growth and ...
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IntroductionThe penetration resistance (PR) of the soil shows the mechanical resistance of the soil against the penetration of a conical or flat probe; it is important in terms of seed germination, root growth and tillage operations. In general, if the PR value of a soil exceeds 2.5 MPa, the growth and expansion of roots in the soil will be significantly limited. The direct measurement of PR is also a laborious and costly task due to instrumental errors. Therefore, it is useful the use of different models such as multiple linear regression (MLR), artificial neural network (ANN) and gene expression programming (GEP) to estimate PR through easily accessible and low-cost soil characteristics. The objectives of this research were: (1) to obtain MLR, ANN and GEP models for estimating PR from the easily accessible soil variables in forest, range and cultivated lands of Fandoghloo region of Ardabil province, (2) to compare the accuracy of the aforementioned models in estimating soil PR using the coefficient of determination (R2), root mean square error (RMSE), mean error (ME) and Nash-Sutcliffe coefficient (NS) criteria. Materials and MethodsDisturbed and undisturbed samples (n = 80) were nearly systematically taken from 0-10 cm soil depth with nearly 50 m distance in forest (n = 20), range (n = 23) and cultivated (n = 37) lands of Fandoghloo region of Ardabil province, Iran (lat. 38° 24' 10" to 38° 24' 25" N, long. 48° 32' 45" to 48° 33' 5" E) in summer 2023. The contents of sand, silt, clay, CaCO3, pH, EC, bulk (BD) and particle density (PD), organic carbon (OC), gravimetric field water content (FWC), mean weight diameter (MWD) and geometric mean diameter (GMD) were measured in the laboratory. Relative bulk density (BDrel) was calculated using BD and clay data. Mean geometric diameter (dg) and geometric standard deviation (σg) of soil particles were computed by sand, silt and clay percentages. The penetration resistance (PR) of the soil was measured in situ using cone penetrometer (analog model) at 5 replicates. Data randomly were divided in two series as 60 data for training and 20 data for testing of models. The SPSS 22 software with stepwise method, MATLAB and Gene Xpro Tools 4.0 software were used to derive multiple linear regression (MLR), artificial neural network (ANN) and gene expression programming (GEP) models, respectively. A feed forward three-layer (2, 5 and 6 neurons in hidden layer) perceptron network and the tangent sigmoid transfer function were used for the ANN modeling. A set of optimal parameters were chosen before developing a best GEP model. The number of chromosomes and genes, head size and linking function were selected by the trial and error method, as they are 30, 3, 8, and +, respectively. The rates of genetic operators were chosen according to literature studies. The accuracy of MLR, ANN and GEP models in estimating PR were evaluated by coefficient of determination (R2), root mean square error (RMSE), mean error (ME) and Nash-Sutcliffe coefficient (NS) statistics. Results and Discussion The studied soils had clay loam (n = 11), sandy clay loam (n = 6), sandy loam (n = 12), loam (n = 13), silty clay loam (n = 14), silty clay (n = 1) and silt loam (n = 23) textural classes. The values of sand (13.14 to 64.79 %), silt (21.11 to 74.96 %), clay (2.95 to 42.18 %), OC (1.01 to 7.17 %), FWC (11.58 to 50.47 mass percent), BD (0.84 to 1.43 g cm-3) and PR (1.03 to 5.83 MPa) showed good variations in the soils of the studied region. There were found significant correlations between PR with FWC (r = - 0.45**), silt (r = - 0.36**) and σg (r = 0.36**). Due to the multicollinearity of silt with σg (r = -0.84**), the σg was not used as an input variable to estimate PR. Generally, 3 MLR, ANN and GEP models were constructed to estimate PR from measured readily available soil variables. The results of MLR, ANN and GEP models showed that the most suitable variables to estimate PR were FWC, silt and BDrel. The values of R2, RMSE, ME and NS criteria were obtained equal 0.44, 1.19 MPa, 0.19 MPa and 0.36, and 0.92, 0.41 MPa, -0.05 MPa and 0.92, 0.79, 0.91 MPa, 0.13 MPa, 0.63 for the best MLR, ANN and GEP models, respectively. The former researchers also reported that there is a negative and significant correlation between PR with FWC. Conclusion The results indicated that field water content (FWC), silt and relative bulk density (BDrel) were the most important and readily available soil variables to estimate penetration resistance (PR) in the studied area. According to the lowest values of RMSE and the highest values of NS, the accuracy of ANN models to predict soil PR was higher than MLR and GEP models in this research.
Research Article
Soil science
N. Mollaei; M. Sheklabadi; M. Nael
Abstract
IntroductionSoil aggregate stability is a crucial indicator for evaluating soil structure, quality, and health. This index affects the physical and hydrological functions of the soil, which, in turn, depend on plant primary production and the capacity of organic carbon decomposition. Soil organic carbon ...
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IntroductionSoil aggregate stability is a crucial indicator for evaluating soil structure, quality, and health. This index affects the physical and hydrological functions of the soil, which, in turn, depend on plant primary production and the capacity of organic carbon decomposition. Soil organic carbon plays a positive role in the formation and stability of soil aggregates. Soil organic carbon (SOC) causes a rapid decrease in water penetration into soil aggregates by creating a water-repellent coating around them and increases their stability against instant wetting stress. Land use and management, including cultivation systems and tillage methods, have an important impact on the stability and size distribution of soil aggregates. Mechanized sugarcane cultivation has a long history in Khuzestan province, particularly in Haft Tepe sugarcane cultivation and industry. Haft Tepe Agriculture is the first sugar production unit in Iran. Despite the increase in the use of chemical fertilizers, the yield of sugarcane crops has been decreasing due to the destruction of the physical properties of the soil. The study aimed to investigate the effects of different sugarcane cultivation systems on soil physicochemical-biological properties and soil stability indices in parts of Khuzestan province. Materials and MethodsSoils were sampled from the surface of five farms in the Haft Tepe sugarcane cultivation complex located in the northwest of Khuzestan province. The farms included single-row, new planting cultivation (S-P); single-row, third ratoon cultivation (S-R3); double rows, new planting cultivation (D-P); double rows, first ratoon cultivation (D-R1); and uncultivated land (barren) that had been left unused for a long time. Soil organic carbon content, active carbon content, basal respiration, induced respiration, water-stable aggregates, and aggregate organic carbon fractions were measured in the sampled soil. Mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates were also calculated. Results and DiscussionThe study found that the organic C content was highest in the double-rows+new planting (D-P) method and lowest in uncultivated land (0.95% and 0.12%, respectively). The increase in plant density, biomass, and plant residue addition in D-P cultivation has led to an improvement in SOC content. The higher SOC content in cultivated lands compared to uncultivated land indicates the positive effect of many years of cultivation and irrigation. Among the different cultivations, double-row new planting (D-P) cultivation had significantly higher active carbon. In D-R1 cultivation, returning plant residues to the soil increased the SOC (0.59%) and active carbon content. The burning of sugarcane plant residues during harvesting and land preparation for new sugarcane cultivation in S-P fields appears to have led to a decrease in active carbon. Basal respiration and induced respiration values were significantly higher in single-row, third ratoon (S-R3) and double-row, new planting (D-P) cultivations, respectively. In S-R3 cultivation, the older plants and increased root biomass provided more rhizospheric organic C for microorganisms, resulting in higher microbial activity and respiration. Microorganisms transform and decompose soil organic matter, which is a source of energy for their metabolic processes. Therefore, there is a close relationship between organic matter and soil microorganisms. Lower basal respiration in newly planted lands may be due to the process of land preparation for cultivation. Additionally, single-row new-planted farms had a clayey texture, which could reduce soil respiration. In general, the recycling of organic matter and microbial activity is lower in fine-textured soils compared to coarse-textured soils. The highest MWD and GMD were found in single-row, third ratoon (S-R3) and single-row, new planting (D-P) cultivations. The uncultivated land had the lowest MWD and GMD, indicating unstable soil structure due to low SOC content. The lower MWD observed in S-P cultivation could be related to tillage and hilling up operations. S-R3 cultivation had more plant residues compared to other cultures. Higher plant ages and increased root biomass and rhizodeposits led to an increase in soil aggregate formation and stability. Soil tillage, which reduces soil organic carbon, can decrease the stability of soil aggregates and structure. The S-P and D-P cultivations had the highest value of coarse aggregates (larger than 2 mm) and fine aggregates (0.53-2 mm). The highest amount of medium aggregates were observed in S-P, D-P, and D-R1 cultivations. Agricultural operations can break large soil aggregates into smaller ones, while low SOC content and burning of sugarcane residues can reduce the formation of large aggregates. The study found statistically significant differences in the OC content of aggregates among the different cultivations. The highest content of aggregates OC was found in coarse aggregates (0.25-2.0 mm) of D-R1, D-P, and S-P cultivations. ConclusionThis study investigates the impact of mechanized and long-term sugarcane cultivation on the physical and biological properties of soil. Overall, the water stable aggregates and MWD were found to be unsuitable in some of the studied fields due to the low amount of SOC. This is primarily caused by the annual burning of sugarcane residue. Therefore, returning plant residues after harvesting is suggested as a significant solution to improve problems related to compaction, soil instability, and their harmful consequences.
