Water and Soil

Abstract Introduction Due to Iran's geographical location and climatic conditions, the quantity and quality of water resources are considered one of the limiting factors for agriculture in this country. Droughts in the last two decades, on the one hand, and lack of attention to the optimal use and proper exploitation of water, on the other hand, have exacerbated the water crisis in Iran. For this reason, the agricultural sector has witnessed serious developments and new perspectives on the rational exploitation of water resources, limited irrigation shortages, the use of saline water resources in agriculture, changing irrigation systems, and cultivating water-intensive plants over the same period. Quinoa has been introduced as a forage crop for ensuring food security in the world, which can tolerate drought stress conditions to some extent. However, the development of its cultivation under drought stress conditions in Khuzestan Province should be based on determining the limits of irrigation water quantities and determining its tolerance to salinity.   Material and Methods The present study was conducted to investigate the effect of different amounts of irrigation water and different levels of salinity on quantitative and qualitative parameters of quinoa. To carry out the work, quinoa was cultivated under drip and pulsed drip irrigation. The treatments studied included irrigation water quantity (I1: 60, I2: 80 and I3: 100% of field capacity), water quality (F (fresh): 0.5 and S (saline): 6 dS/m), and two irrigation managements: continuous drip (C) and pulsed drip (P). At the end of the growing season, sampling was performed to determine quantitative plant characteristics such as height, stem diameter, leaf area index, root length, root volume, fresh and dry root weight, and fresh and dry forage yield. Also, to investigate the effect of treatments on quinoa forage quality, qualitative parameters including leaf chlorophyll a and b content, leaf proline content, total digestible nutrients (TDN), crude protein (CP), Neutral detergent fiber (hemicellulose and lignin) (NDF), and Acid detergent fiber (hemicellulose-free cell wall) (ADF) percentage were measured. To investigate the distribution of salinity in the soil profile during and at the end of the growing season compared to its beginning, soil samples were taken from dug profiles in the center of all experimental plots at depths of 0-30 cm and 30-60 cm. These samples were transferred to the laboratory and saturated extraction was prepared from them. Then, the electrical conductivity of these samples was determined using an EC meter. All data collected from the experiment were entered into EXCEL 2019 software. After categorizing the data, SAS 9.1 software was used to analyze them. Data analysis of variance was performed at the 5% and 1% significance levels, and then means were compared using Duncan's multiple range test.   Result The results showed that the treatments of continuous drip irrigation with fresh water at 100% depth, and pulsed drip irrigation at 100% depth (first, second and, third pulses of fresh water) had the highest quantitative traits. Continuous drip irrigation with fresh water at 80% depth, and pulsed drip irrigation at 80% depth (first, second and, third pulses of fresh water) also had high quantitative traits. The highest values of plant height, stem diameter, leaf area index, fresh biomass, and dry biomass were 94 cm, 1.10 mm, 23.152 cm², 25.31420, and 14.8256 tons per hectare, respectively, which were obtained from the continuous drip irrigation treatment at 100% of the plant's water requirement using fresh water. In these treatments, the final soil salinity was close to the initial salinity at the time of the experiment, and the highest amounts of chlorophyll a and b and carotenoids were also observed. The TDN and ADF values were high in two treatments: continuous drip irrigation with fresh water and 100% depth, and pulsed drip irrigation and 100% depth (first, second and, third pulse of fresh water). However, these treatments had low soluble sugar, proline, and protein levels. Applying saline water alone or in combination with sweet pulses and water stress in treatments 2, 4, and 12- 30 increased the quality of the produced forage (due to high soluble sugar, proline, and protein). The highest water use efficiency was obtained from treatment 26, which included pulsed drip irrigation and a depth of 60% (first pulse of fresh water, second pulse of salin water, third pulse of fresh water).   Conclusion Therefore, considering that both water use efficiency and quality are important in forage production, it is recommended to use this treatment under conditions of saline water and pulsed drip irrigation.

Abstract Introduction Increasing the quality of food grains is one of the goals of sustainable agriculture. Mung bean (Vigna radiata L.) is one of the most important legume crops cultivated on more than 6 million hectares worldwide. There are few studies on the effect of mealworm frass application and its effectiveness on plant growth and yield. On the other hand, given the soil and climatic conditions of Iran, its high potential in legume production, and its economic justification, it seems necessary to pay attention to feeding mung beans with organic fertilizers. The cultivation of mung bean is increasingly developing in Iran, and its use for food and medicinal purposes is also increasing. Therefore, considering the possible positive effect of mealworm frass and zinc fertilizer on the growth of this plant, the present study was conducted to investigate the effect of these fertilizers on growth, yield indices, and the molar ratio of phytic acid to zinc in the seeds.   Materials and Methods In this study, an experiment was conducted as a factorial experiment in a randomized complete block design with three replications. The aim was to investigate the effect of different levels of mealworm frass and zinc lignosulfonate foliar application on growth characteristics, yield, zinc concentration, the molar ratio of phytic acid to zinc, and some biochemical factors of mung bean seeds. The treatments included four levels of mealworm frass (0, 500, 1000 and 1500 kg ha^-1) and three levels of zinc foliar application during the flowering period (foliar application with irrigation water as a control and foliar application with concentrations of 2.5 and 5 g L^-1 of zinc lignosulfonate). Growth and yield indices including plant height, number of secondary stems, number of pods per plant, number of seeds per pod, pod length, and seed yield were measured. Also, some biochemical properties such as molar ratio of phytic acid to zinc, flavones, total flavonoids, total phenols, tannin concentration and percentage of antioxidant activity were measured. Nitrogen, phosphorus and potassium of mung bean seeds were also measured.   Results and Discussion The results showed that the simple effect of mealworm frass was significant for all measured traits except the number of secondary stems, pod length, and number of seeds per pod. The simple effect of zinc lignosulfonate was significant for all measured traits except the number of secondary stems, pod length, number of seeds per pod and total phenol concentration, and seed tannin. The interaction effect of mealworm frass and zinc lignosulfonate for all measured traits except pod length and number of seeds per pod was significant. The highest grain yield (115.2 g m^-2) was related to the treatment of 1500 kg of mealworm frass and 5 ppt zinc lignosulfonate foliar spray, which was in the same group as the treatment of 1500 kg mealworm frass with 0 and 2.5 g L^-1 zinc foliar spray, and the treatment of 1000 kg mealworm frass and 5 g L^-1 zinc foliar spray. While the lowest amount (80.1 g m^-2) was observed in the control treatment. The highest plant height (37.05 cm) was measured in the treatment of 500 kg mealworm frass with zero zinc application, and the lowest stem length (24.68 cm) was observed in the treatment of 500 kg of mealworm frass with the application of 5 g L^-1 zinc. The highest molar ratio of phytic acid to zinc (30.8) was observed in the treatment of 500 kg of mealworm frass and no foliar application of zinc lignosulfonate, which was not significantly different from the treatments of 0 kg of mealworm frass and 0 and 2.5 g L^-1 of zinc lignosulfonate application. While the lowest ratio (24.1) was observed in the treatment of 0 kg of mealworm frass and 5 g L^-1 zinc lignosulfonate application, which was not significantly different compared to the treatment of 1500 kg of mealworm frass and 2.5 and 5 g L^-1 of zinc lignosulfonate application. Foliar application of zinc reduced the molar ratio of phytic acid to zinc in the grain (maximum 21%), and application of mealworm frass increased this ratio up to 500 kg and then decreased it. Based on the results of this study, the application of 1000 kg of mealworm frass without zinc application was more effective in increasing the concentration of flavonoids and antioxidant activity. However, zinc foliar application was effective in increasing the concentration of phenolic compounds and tannin. The highest antioxidant activity (72.44%) was observed in the treatment of 1000 kg of mealworm frass without foliar application of zinc, and the lowest (58.18%) was measured in the treatment of 1500 kg of mealworm frass and application of 2.5 g L^-1 zinc lignosulfonate, followed by treatments of 500 kg of mealworm frass without foliar application of zinc lignosulfonate and foliar application of 2.5 g L^-1 zinc lignosulfonate. Zinc foliar spraying was effective in increasing the concentration of phenolic compounds and tannin content. Foliar application of zinc lignosulfonate increased the zinc and nitrogen content of the grain but had no effect on the phosphorus and potassium concentrations. Application of mealworm frass increased the nitrogen, phosphorus, and potassium content of the mung bean grain but simultaneously reduced the zinc concentration.    Conclusion In general, the results of this study showed that the use of mealworm frass increased mung bean grain yield, and foliar spraying of zinc lignosulfonate increased the grain zinc concentration and reduced the molar ratio of phytic acid to zinc. Overall, the use of mealworm frass increased the yield, and the use of zinc lignosulfonate improved the grain quality.

Abstract Introduction Potassium is one of the macronutrients essential for plant growth and plays significant physiological and biochemical roles in plant yield. There are four forms of potassium in the soil, listed in order of their availability for plant uptake: soluble potassium, exchangeable potassium, non-exchangeable potassium, and structural potassium. Determining the concentration of available potassium using an efficient extractant that is applicable to different soil types is essential for soil and crop management, such as fertilizer recommendations. One of the most common extractants for available potassium is 1N ammonium acetate (NH₄OAc). This extractant is widely used in many soil science studies and fertilizer recommendations due to its ability to extract exchangeable potassium and a portion of non-exchangeable potassium  However, this method may not have sufficient accuracy to measure the potassium readily available for plant uptake. In soils with high amounts of potassium-containing minerals, due to the presence of specific adsorption sites, a large portion of potassium is held strongly at these sites and can be partially extracted during NH₄OAc extraction. This issue could be one reason for the weak correlation between NH₄OAc-extracted potassium and plant response to potassium fertilizer in such soils. The critical level of available potassium is the threshold below which plant growth is limited. Since the amount of potassium extracted depends on the concentration of the extractant, evaluating the effect of different NH₄OAc concentrations on the determining the critical level is important. The objective of this study was to assess the impact of various NH₄OAc concentrations on the extraction of available potassium and to determine the critical potassium level in the calcareous soils of Shahrekord Plain.   Material and Methods In order to evaluate different concentrations of NH₄OAc of the calcareous soils of the Shahrekord plain, 30 agricultural soil samples were collected from a depth of 0–30 cm. Four different concentrations of NH₄OAc including 1, 0.5, 0.25, and 0.1 molar were evaluated for extracting available potassium. The greenhouse experiment was carried out as a factorial experiment in a completely randomized design with two factors (soil type and potash fertilizer rate) and three replications. The potash fertilizer (potassium sulfate) was applied at two levels of potassium: 0 and 100 mg K kg⁻¹. At the end of the vegetative period, corn plants were harvested, and plant indices including dry matter weight, potassium concentration, potassium uptake, relative yield, and plant response were determined. To assess the significance of treatment effects in terms of plant indicators, factorial analysis of variance was performed. Then, the correlation between plant indices and potassium extracted using different concentrations of NH₄OAc was calculated, and based on the results, the most suitable concentration for extracting available potassium by NH₄OAc was determined. The potassium critical level was determined using the Cate-Nelson graphical method for NH₄OAc extractants with concentrations of 1, 0.5, 0.25, and 0.1 molar.   Results and Discussion The results showed the range of available potassium extracted using NH₄OAc extractants at concentrations of 1, 0.5, 0.25, and 0.1 molar was 157–581, 155–598, 160–596, and 168–590 mg kg⁻¹, respectively. Furthermore, the results showed that the differences among the mean values of potassium extracted at different concentrations of ammonium acetate were not statistically significant. The results of the analysis of variance showed that the main effects of soil type and potassium fertilizer were significant (p<0.01) for dry matter weight, potassium concentration and uptake. However, the interaction between soil and fertilizer was not significant for dry matter weight. Based on the strong correlation between potassium extracted by NH₄OAc at concentrations of 1, 0.5, 0.25, and 0.1 molar and the relative yield and plant response indices, these concentrations can be considered suitable for use in these soils. By using the Cate-Nelson graphical method, the potassium critical level with concentrations of 1, 0.5, 0.25, and 0.1 molar was 250, 250, 255, and 250 mg kg^-1 respectively.   Conclusion The results showed that reducing the concentration of ammonium acetate does not affect the efficiency of this extractant. The results showed that the amounts of available potassium extracted with NH₄OAc at different concentrations were close to each other, with less than one percent difference. Commonly, NH₄OAc 1 M is used for extracting available potassium; however, our results show that lower concentrations of NH₄OAc (0.5, 0.25, and 0.1 M) can be effectively used as a substitute to the 1 M solution. Therefore, it is recommended to use 0.1 molar ammonium acetate for the extraction of available potassium. This substitution could result in a considerable reduction in chemical consumption.   Acknowledgements The authors would like to thank the Soil Science Department of the University of Shahrekord for providing 

Abstract Introduction Soil erosion is the most important cause of land degradation in the world, which threatens the sustainable use of the world's soil resources, especially in semi-arid regions. Despite the important implications of soil erosion in sustainable land use, there is limited information about soil erosion in Iran’s watersheds. The lack of this information is related to the complexity of erosion processes, which makes predicting soil erosion costly, time-consuming and difficult. This difficulty has led to the development of various models and tools that seek to simplify soil erosion models and improve our understanding of soil erosion patterns and processes. In recent years, with the development of computer technologies, the evaluation of different machine learning algorithms used in creating predictive models has become the focus of researchers. Machine learning models have been used in numerous studies and have proven as a helpful tool for assessing and mapping various types of water-induced soil erosion. Accordingly, machine learning methods could be used to study the K-factor to identify the areas with higher soil erodibility potential. This research aimed to model and predict the soil erodibility coefficient using various machine learning methods, introduce the most important parameters affecting the prediction of this factor, as well as predict soil erosion using the RUSLE model, and ultimately present a soil erosion risk map in part of the lands of central Iran.   Materials and Methods The Revised Soil Loss Equation (RUSLE) model, which estimates annual soil erosion rate and evaluates erosion risk by considering five factors rain erosivity (R), soil erodibility (K), slope length and percentage (LS), vegetation cover (C) and conservative operations (P) was employed in this study. Across the study area, 100 points were sampled using the cLHS method to calculate the spatial variations of the K factor. Some of the soil properties including soil organic matter, primary particle size distribution, soil structure stability, and saturated hydraulic conductivity were measured in the laboratory to aid in the K factor calculation. Subsequently, the K factor was estimated using three machine learning methods (SVM, Cubist, and RF) and a map of its spatial variations was predicted. R factor estimated using data from five climatic stations located within and outside the watershed. The LS factor derived from a digital elevation model (DEM) with 12.5 × 12.5 m resolution. The P factor was considered as 1, while the C factor calculated from the NDVI map. Finally, all factors were integrated into the RUSLE model using ArcGIS to estimate the average annual soil loss.   Results and Discussion The results of the effective factors in soil erosion showed that the western parts of the studied basin have more rainfall than the eastern part of the region. The value of soil erodibility factor in agricultural lands and also in highlands due to the topographical conditions had higher values than the pastures of the study area. The length and percentage of the slope are other effective factors in the calculation of soil erosion. Moreover, the findings confirmed that the amount of soil erosion increased significantly with the increase of the slope. The vegetation factor exhibited high diversity across the region, with low values in areas of proper vegetation like agricultural lands near the river, and high values in degraded pastures. In the study area, no conservation measures, including cultivation on contour lines, strip cultivation, and traces or implementation of banquets, had been carried out. The soil erosion in the central parts of the study area, which includes plains and lands with topographical changes and low slope, had a lower amount than the high lands on both sides of the watershed. In addition to topography, issues such as the loss of vegetation in pastures due to over-grazing and poor management are the main drivers of soil degradation and high erosion in these areas. Various inappropriate management practices, unprincipled cultivation and tillage, the conversion of pastures to low-yielding rainfed agriculture, and excessive grazing are primary drivers of soil degradation in the study area. Factor K modeling results indicated that the random forest model generally exhibited higher performance compared to Cubist and SVM models in almost all machine learning modeling. In all cases, the combination of all environmental variables, including remote sensing indicators, topographic features, and thematic maps (third scenario), resulted in the highest spatial modeling performance. The results of the implementation of RUSLE model showed that the soil erosion rate for the study area was 8.27 ton/ha/yr. The erosion risk map was prepared using the RUSLE model for the study area and revealed that the critical parts of soil erosion are located at the northeastern part of the basin, which should be given special attention in the executive operations related to watershed management. According to this map, about half of the study area has very low and low erosion, but about 21% of the study area is in severe and very severe soil erosion classes, which require urgent measures to prevent sediment production in the sub-basin.   Conclusion In predicting soil erodibility coefficient with DSM method, RF model had better results than Cubist and SVM models. Implementing RUSLE model estimated soil erosion rate of the study area to be 8.27 ton/ha/yr. Soil erosion classes were weak, moderate, severe and very severe with about 33, 20, 26, 18 and 3% respectively. About 21% of the basin was classified as severe and very severe, which require urgent soil conservation measures.

Abstract Introduction Wheat is the principal crop in Iran in terms of both production and cultivated area. Enhancing its production is critically important for the economy and national food security. Assessing the water productivity of commercial wheat varieties is key to achieving more efficient water use. Previous studies have demonstrated that wheat water productivity is influenced by cultivar type and irrigation amount, with different varieties exhibiting varying grain yields under both water deficit and surplus conditions. Increasing yield and water productivity depend on several factors, most notably the selection of high-yielding, improved cultivars with lower water requirements, coupled with irrigation management strategies tailored to the characteristics of these varieties, especially in hot and arid climates.   Materials and Methods A two-year field experiment was conducted during the 2021-2022 and 2022-2023 growing seasons at the Safiabad Agricultural and Natural Resources Research and Education Center, using a randomized complete block design with three replications. The experimental treatments consisted of five irrigation levels (25%, 50%, 75%, 100%, and 125% of crop evapotranspiration) as the horizontal factor and six bread wheat cultivars (Azadegan, Ouj, Barat, Jalal, Darion, and Mehregan) as the vertical factor. Following land preparation, fertilization with macronutrients was applied before planting and during the vegetative growth stage, based on soil test recommendations. Sowing was performed using a Wintersteiger row planter, and irrigation was supplied via a T-tape drip irrigation system. Water was sourced from the Dez irrigation and drainage network. The designated irrigation treatments were implemented starting from the third irrigation event, with water volumes measured using volumetric water meters. Crop evapotranspiration was calculated using the evaporation pan method, and soil moisture balance was monitored by auger sampling and the gravimetric method. Weed control was achieved through appropriate herbicide applications.   Results and Discussion In the first and second years, total evapotranspiration (ET) was 310 mm and 300 mm, while total rainfall was 145 mm and 289 mm, respectively. Accounting for effective rainfall, the irrigation treatments supplied 42, 62, 82, 102, and 122% of the crop ET in the first year, and 60, 76, 89, 103, and 117% in the second year. A combined analysis of variance revealed a significant year effect. The grain yield of the cultivars in response to ET showed maximum variations of 10% and 30% in the first and second years, respectively. Water productivity, measured as grain yield per millimeter of water consumed, ranged from 18.43 to 22.38 kg ha⁻¹ mm⁻¹. By selecting an appropriate cultivar and managing deficit irrigation, the applied water productivity and crop water productivity indices increased by 63% and 93%, respectively. The relationship between plant water supply and grain yield followed a quadratic function. Based on this model, the optimal deficit irrigation strategy was to supply 70% of wheat ET, which resulted in an acceptable grain yield reduction of approximately 15%. Across irrigation treatments in both years, the Darion, Mehregan, and Jalal cultivars exhibited higher average grain yield and crop water productivity than the mean of all cultivars. A cluster analysis was performed using R software, based on the regression coefficients of the grain yield, relative water supply, and evapotranspiration data. The cultivars were grouped into distinct clusters, and practical, cluster-specific management recommendations are provided.   Conclusion Hot and dry climates are characterized by high variability in evaporation, precipitation patterns, and crop water requirements across different wheat growth stages. Consequently, to achieve sustainable production and enhance water productivity within the genetic potential of wheat varieties, breeding programs should target the development of cultivars capable of producing more than 24 kg of grain per hectare per millimeter of water consumed.

Abstract Introduction  Phosphorus (P) is an essential nutrient for plant growth. In calcareous soils, the presence of calcium carbonate affects the availability of phosphorus to plants. Due to the special behavior of phosphorus and its low availability in calcareous soils of Iran, the need to identify crop varieties that are efficient in absorbing and utilizing this nutrient is vital. On the other hand, following the global fertilizer crisis and the sharp increase in input prices, focusing on efficient fertilization strategies has become an important priority. Among oilseed plants, sesame (Sesamum indicum) ranks fifth in the world and second in Iran in terms of oil production. Despite its economic importance, sesame has received less attention in phosphorus nutrition management studies. Therefore, this research was designed and implemented with the aim of providing a practical solution to improve yield per unit of phosphorus consumed, as a necessary step towards increasing farmers' profitability and strengthening the country's food security.   Materials and Methods This study was conducted as a factorial experiment in a randomized complete block design at Darab Agricultural Research Station, Fars Province, for two years during the 2019 and 2020 growing seasons. Soil available phosphorus was below the optimal range and the irrigation system used was drip irrigation. The soil texture was relatively heavy, the percentage of soil organic carbon was low, and the equivalent calcium carbonate was high. The soil was non-saline and the amount of available phosphorus and zinc was insufficient. The irrigation water was non-saline. The treatments studied included five phosphorus levels (0, 5, 10, 15, and 20 kg ha^-1 of phosphorus from a triple superphosphate source with 20% phosphorus) and two sesame cultivars, Darab 14 and Darab 1. The phosphorus levels, along with 50% of nitrogen fertilizer, 50 kg ha^-1 potassium sulfate and 30 kg ha^-1 of zinc sulfate were applied before planting. The remaining required nitrogen fertilizer (50 kg ha^-1 of urea) was applied before flowering. At the harvest stage, yield and yield components, phosphorus and micronutrients concentrations in the grain were measured. Nutrient uptake in the grain, seed oil percentage, and phosphorus efficiency indices of the grain were also determined.   Results and Discussion Based on the two-year average results, the grain and oil yield of the Darab 14 cultivar were 20.4% and 30.6% higher than those of the Darab 1 cultivar, respectively. The number of capsules per plant, the number of seeds per capsule, grain yield, and oil yield increased significantly up to the application level of 10 kg of phosphorus per hectare (by 23.5%, 20.4%, 42.7%, and 52.9%, respectively), although they showed no significant difference compared with the 5 kg P ha⁻¹ treatment. Therefore, for these cultivars, the application of 5 kg P ha⁻¹ is recommended in terms of grain and oil yield. Measurement of seed phosphorus concentration at different phosphorus levels indicated that a range of 0.25% to 0.28% can be considered as the seed phosphorus sufficiency threshold for these cultivars. Over the two-year average, the uptake of phosphorus, nitrogen, iron, manganese, and zinc was higher in Darab 14 than in Darab 1. The maximum uptake of nitrogen was recorded at 10 kg P ha^-1 (49.3 kg ha^-1), which was significantly different from the control treatment (36.3 kg ha^-1). However, with further increase in phosphorus application, the amount of nitrogen uptake decreased. The maximum uptake of iron occurred at 10 kg P ha^-1, but was not significantly different from the level of 5 kg P ha^-1. For the elements manganese, zinc, and copper, the maximum uptake was also recorded at 10 kg phosphorus/ha. Further increase in phosphorus application rate decreased the uptake of these elements. The uptake of zinc at 20 kg P ha^-1 decreased by about 4.9% compared to the control treatment. At all phosphorus application levels, Darab 14 outperformed Darab 1 in terms of grain yield, phosphorus uptake, and phosphorus use efficiency. Darab 14 produced a higher yield per unit of phosphorus applied compared to Darab 1. Sesame seed yield was positively and significantly correlated with seed phosphorus uptake (0.82^**). Sesame is known for its strong root system and low nutrient requirements, but the present study showed that sesame's ability to uptake phosphorus is limited at this level of available phosphorus (8.2 mg kg^-1). Seed yield was significantly correlated with nitrogen uptake (0.82^**), iron uptake (0.59**), manganese uptake (0.86^**), zinc uptake (0.75^**), and copper uptake (0.73^**).   Conclusion By cultivating phosphorus-deficiency tolerant cultivars such as Darab 14, along with minimal phosphorus fertilizer application (5 kg ha⁻¹ under the present experimental conditions), farmers can not only achieve optimal yield but also significantly enhance profitability and increase resource use efficiency in calcareous soils with phosphorus deficiency. For farmers, grain yield is more important than oil yield because sesame seeds are purchased based on seed weight rather than oil content. This results in a more favorable profit-to-cost ratio based on the harvested seed weight.   Acknowledgements This project was part of the National Project of the Soil and Water Research Institute. The cooperation of this institute, as well as the cooperation of the Darab Agricultural Research Station of Fars Province, and the General Directorate of Cotton and Oilseeds of the Ministry of Agricultural Jihad for providing project fundingis gratefully acknowledged.