JWSS - Journal of Water and Soil Science

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Nitrogen fertilizer application for corn (Zea mays L.) based on available N of soil can decrease the need to N fertilizer and, consequently, reduce the risk of environmental pollution, especially that of groundwater and drinking water. The objectives of this study were i) determining soil N0₃-N critical level at 4 to 6 leaf stage, ii) to study soil nitrate distribution, iii) determining N rate required for maximum corn grain yield, iv) measuring soil residual nitrate nitrogen after harvesting, and v) using hand chlorophyll meter to evaluate N status of corn. The experiment was conducted under field conditions in Bajgah and Kooshkak research stations (Fars Province) in 1996 using a split plot randomized complete block design with four replications. Main plots were control, 60, 120, and 180 kg N ha^-1 as urea. At 4 to 6 leaf stage each main plot was divided into two sub-plots and N was applied at 60 kg N ha^-1 rate to one sub-plot and the other sub-plot was left as control.

 Results showed that critical soil N0₃-N level at 4 to 6 leaf stage in 0-30 cm depth for 90 percent relative yield in Bajgah was 12-14 and for Kooshkak was 8-10 mg kg^-1 soil. The highest coefficient of determination between corn grain yield and soil N0₃-N in 0-30 cm depth for Bajgah was in furrow sample and for Kooshkak was in furrow and shoulder composite sample. In both sites, maximum corn grain yield, with 15.5% moisture content, was about 14 mg ha^-1 that was obtained through the application of 120 kg N ha^-1 as preplant plus 60 kg N ha^-1 as sidedress which is about 1/2 of the application rate used by local farmers. The highest residual soil N0₃-N after harvesting was 24 and 18 and the lowest was 2.6 and 3 mg kg^-1 soil for Bajgah and Kooshkak soils, respectively. When maximum corn grain yield was obtained, chlorophyll meter reading at the middle of leaf blade at dough stage, was 49 for both sites. It seems that N fertilizer application rate by local farmers is excessive.

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Watermelon (Citrullus Lanatus) cv. Charleston Gray is one of the most important cultivars grown in Iran. It has some good quantitative and qualitative characteristics but unfortunately is sensitive to Blossom End rot. To solve this problem, this experiment was conducted in a factorial manner in randomized complete block design with four replications in Research Station and Laboratories of Department of Horticulture, College of Agriculture, the University of Tehran, during 1997 & 1998. In this experiment, black polyethylene mulch was used and calcium nitrate was foliar sprayed at concentrations of 0, 4, and 6 g/L. Results indicated that mulch could increase yield by 85% over two years due to weed growth suppression and conserving soil moisture for a longer time. Foliage fresh weight, number and average weight of fruits per plant and precocity were also significantly affected by black polyethylene mulch. Furthermore, mulch reduced the number and weight of fruits affected by Blossom End rot by about 13% and 12.5% (average of two years), respectively. Calcium nitrate addition during both years had no significant effect on the measured fruit characteristics nor on Blossom End rot.

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In recent decades, the use of nitrogen fertilizers has increased irrespective of their effects on soil properties, agricultural products and, particularly, on environmental pollution. Nitrate easily leaches from soils into groundwater. The objective of this study was to determine temporal and spatial nitrate concentrations in groundwater in agricultural, industrial and urban regions in some parts of Isfahan Province. Water samples were collected monthly from 75 agricultural, industrial, and urban wells of Isfahan, Najaf-abad, Shahreza, Natanz and Kashan during January-May 2001. The results indicated that NO₃-N concentrations in most of the regions studied were higher than the standard level (10 mg/l) and nitrate pollution must be reckoned among the most serious problems of sustainable agriculture and exploitation of groundwater resources. Average NO₃-N concentration in different wells ranged from 1.03 to 50.78 mg/l (4.64 to 228.5 mg/l as nitrate). The average NO₃-N concentration in groundwater of Najaf-abad, Shahreza, Isfahan and Natanz-Kashan was 17.56, 14.6, 16.04, and 8.24 mg/l and 95.5, 100, 84 and 33.3 % of total wells in these regions had nitrate concentrations above the standard level, respectively. Maximum NO₃-N concentration was detected in the agricultural region south of Najaf-abad (64.6 mg/l). Nitrate pollution in most of the sampling areas was mainly linked to agricultural activities. The average NO₃-N concentration in groundwater of all agricultural, industrial, and urban regions, except for urban regions of Natanz and Kashan, were above the standard level. Generally, nitrate concentration level in groundwater increased with time and was maximum in March and April.

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Tuberose is one of the tropical and subtropical bulbous cut flowers cultivated extensively in most floricultural regions of Iran. Although it has a high potential for a long vase life after harvest, tuberose declines rapidly at home. In order to overcome this problem, two experiments were conducted on a local cultivar, “Goldorosht-e-Mahalat”, using a completely randomized design. To find a suitable preservative which provides the longest vase life for tuberose, the experiment was carried out by applying the carelessness of most consumers: not recutting stem ends nor changing the vase solutions. In the first experiment the preservative solutions were: sucrose (1, 2 and 3%), silver thiosulphate (0.4, 0.8 and 1.2 mM), silver nitrate (50, 100 and 150 mgl^-1), citric acid (150, 300 and 450 mgl^-1) and tap water as the control. In the early days of the experiment, silver thiosulphate caused severe burning of the florets, silver nitrate caused the wilting of the florets and bent the end of the flower spikes and sucrose didn’t have any positive effect, but decreased the vase life. The longest vase life belonged to citric acid, after which the control (tap water) was placed. The second experiment was conducted to determine the role of the water quality and citric acid. The treatments were: sterilized distilled water, citric acid made with sterilized distilled water (150, 300 and 450 mgl^-1) and tap water as the control. The longest and the shortest vase life belonged to sterilized distilled water and the control (tap water) respectively. The citric acid prepared with sterilized distilled water had a desirable effect on the vase life of cut tuberose flowers. This effect increased with the increment of the acid up to 450 mgl^-1.

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Fertilizers in agriculture are potential sources of environmental pollution, especially in ground water quality and soil resources. Studying factors effective in water and nutrient transport through soil profile is helpful for nutrient management to minimize adverse impacts on environment and nitrate leaching below the root zone. In this study, the ground water level and nitrate leaching transportation below the root zone were measured in a paddy rice field and the data were simulated with the DRAINMOD-N model. For evaluating DRAINMOD-N software in a paddy rice field under surface drainage in Mazandaran, the ground water level and nitrate transportation were measured during four months (June, July, August and September) in 2008. The DRAINMOD-N model was calibrated by adjusting nitrification and denitrification rate constants to reach the best fit between measured and predicted data. Results indicate that predicted ground water level and nitrate concentration by model were significant at one percent level. The statistical comparison was done by model efficiency (EF) 0.84 for estimation of ground water level and 0.97 for estimation of nitrate concentration, respectively. The DRAINMOD-N model can be used as a tool to manage environmental pollution of nitrate in paddy rice fields.

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The effect of sugarcane straw anion exchanger with Micro and Nanostructure scale as the adsorbent for contaminated water treatment was investigated. The effects of operating conditions such as adsorbent loading, initial anion concentration, pH and the presence of competitive ions on the adsorption performances were examined. Equilibrium time and pH and adsorbent dosage were 3h, 6 and 0.5g respectively. The effect of initial concentration on the adsorption of NO3- ions by sugarcane straw anion exchanger was investigated by varying solution concentrations (5-120 mg L-1) using 0.5g adsorbent dose. For micro and nanostructures, adsorption capacity was (0.38-6.94 mg g-1) and (0.44-7.51 mg g-1) respectively. In the column experiment, for micro and nanostructures with (15, 50 and 120 mg L-1) and 0.98 L hr-1 flow rate, adsorption capacity was (8.73, 25.71and 36.25 mg g-1) and (12, 27 and 48.15 mg g-1) respectively. The result of this study indicated that sugarcane straw anion exchanger with micro and nanostructure scale could be used for the removal of nitrate ions in the contaminated water treatment. sugarcane straw anion exchanger -nanostructure adsorbent had higher adsorption than micro adsorbent for nitrate removal.

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Nitrate leaching from agricultural lands can pollute groundwater, and the degree of pollution caused significantly depends on agricultural practices implemented on farms. Field studies required to evaluate the effects of various agricultural management strategies on nitrate leaching are expensive and time consuming. As a result, it is suggested to use crop models to simulate the effects of management practices on nitrate leaching. Plant growth models such as DSSAT software package can simulate daily plant growth and development, and also are capable of simulating daily nitrate leaching and nitrogen uptake by plants. However, it is required to evaluate the performance of any model before using it for any specific region. In this study, the performance of nitrogen balance model of DSSAT software package was evaluated to simulate nitrate leaching from the root zone of silage maize at different levels of applied water and nitrogen fertilizer. The experiment consisted of three levels of nitrogen fertilizers, including zero, 150 and 200 kg N ha-1 and four levels of applied water 0.7SMD (soil moisture depletion), 0.85SMD, 1.0SMD and 1.13SMD. Nitrate-nitrogen leaching from 36 plots at the 60 cm depth during the growing period was measured by soil moisture suction equipment (ceramic suction cups, CSC). After calibrating the model by using field data, its performance was evaluated to simulate nitrate leaching. Maximum amount of N leaching 8.4 kg N ha-1 was obtained from over irrigation treatment with the application of 150 kg nitrogen per hectare. The model simulated nitrate leaching for this treatment as 7.8 kg N ha-1. The model consistently underestimated the nitrate leaching however, it followed the behavior of nitrate leaching during the growing season. In deficit irrigation treatments, the nitrate leaching was very low and close to zero and the model simulated the same result accordingly. The results showed that the model, in addition to phenological stages and performance indicators, can simulate nitrate leaching from the root zone and could be used to evaluate the effects of various irrigation and fertilizer management strategies on nitrate leaching.

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Nitrogen (N) loss from irrigated cropland, particularly sandy soils, significantly contributes to nitrate contamination in surface and groundwater and increases N applications to crops. This is because negatively charged nitrate normally does not have much affinity to soil particles. To retard the movement of nitrate, materials should have high affinity for anions, which most naturally occurring minerals do not have. The cation-exchange properties of natural zeolites can be exploited to modify their surface chemistries so that other classes of compounds, particularly anions and non-polar organics are retained. In this study, the ability to remove nitrate from aqueous solutions with different Cl- concentrations using Iranian zeolite (Semnan) modified by hexadecyltrimethylammonium bromide in millimeter and nanometer particle sizes was determined and the equilibrium isotherms were characterized. The nitrate release as affected by time and ionic strength was also evaluated. It was demonstrated that SMZ is capable of adsorbing more than 60 mmol kg-1 and 80 mmol kg-1 nitrate in millimeter and nanometer sizes, respectively, and adsorbed nitrate can be easily released under different ionic strengths. The millimeter and nanometer-sized SMZ showed 26.7% to 82.3% and 37.8% to 85.5% nitrate removal efficiency, respectively. The average of nitrate released by millimeter-sized SMZ was 6.92 mmol kg-1 in deionized water while it was 14.68, 22.71, and 34.91 mmol kg-1 in releasing solutions with ionic strengths of 0.03, 0.1, and 0.3 M, respectively

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The incorporation of plant residues in soils of arid and semiarid regions is a major principle of sustainable agriculture. This study was conducted at the research farm of Urmia University (37° 32’N and 45° 5’ E), Urmia, Iran during the 2009 and 2010 growing seasons. Five green manure crops were grown in four replications arranged in a randomized complete block design. The treatments included white clover (T.repens), sainfoin (Onobrychis viciaefolia), pearl millet (Panicum miliaceum), sorghum (Sorghum bicolor) and turnip (Eruca sativa). Changes in soil nutrient elements and nitrogen mineralization were measured during different time periods after plant residues incorporation to soil. The plants were irrigated 50% of field capacity during growing period. The results showed that the total nitrogen and NH4-N were influenced by type of green manure in both years. The lignin and cellulose were the main factors controlling N mineralization and residue decomposition. In the first and second year, the results indicated that pearl millet green residues resulted in the highest amount of soil organic carbon. Nitrate-N content reached the highest amount in sainfoin and white clover. In conclusion, white clover and sainfoin due to increasing total and mineral nitrogen for subsequent plants could be introduced as a proper green manure in water deficit conditions.

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Shahrekord aquifer is depleted by almost 800 deep and semi-deep wells, the majority of which are agricultural wells and some have urban usage. In southern parts of the plain, the water table has fallen strongly because of immoderate discharge and decreased the quality of water by urban wastewater. The main objective of this study is investigation of subsurface dam construction and its effects on water table in consumption locations, reduction of deliveries costs and interception of contaminant transport. Therefore, the Shahrekord aquifer model was simulated with hydrodynamic coefficients calibration by PMWIN5.3 Software. The southern outlet of plain (near Bahram-Abad village) was selected to study subsurface dam construction, then a horizontal-flow barrier in this place was set with mean hydraulic conductivity equal to 0.5 m/day. Water table situation and nitrate concentration were analyzed using ArcGIS9.2 software before and after dam construction. The results showed that the subsurface dam rises groundwater level in 4 kilometers distance of upstream areas. Also, the available volume of water increased about 1.5 Mm3. Nitrate concentration didn't show to be considerably different from the initial state. But, it is likely that contamination in the storage resource will rise because it is located near Shahrekord water treatment plant and also due to the discharge of wastewater wells.

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Zeolites are substances that have been renowned for their remarkable nitrogen adsorption capacity resulting of decrease in leaching rate of soil nitrogen. This research was conducted to study the effect of the zeolite dosage, zeolite particle size and the method of application on the nitrate leaching of the soil irrigated by treated wastewater (TWW). All of the adsorption tests were carried out in a 27 PVC columns with 11 cm diameter and 60 cm length. The experiments were consisted of 9 treatments and 3 replications including 2 zeolite application method (mixed and layered), 2 zeolite’s grain size (63-125 and <63 micrometer) and 2 zeolite dosage (2 and 4 percent). Zeolite powders were added to the soil in mixed or layered fashion. The soil columns were irrigated 13 times with TWW in a weekly period. In the 4th, 9th and 13th irrigation event, three samples were taken from input and output TWW introduced to columns to measure the change in nitrate concentration. The results were shown that nitrate absorption rate was increased by average of 164.3% and 350.7% in mixed and layered treatments, respectively compared to the control. The result showed that zeolite application method, irrigation event, zeolite’s grain size and dosage were statistically significant on nitrate absorption efficiency (P<0.01). It shows that as the zeolite size decrease the soil nitrate adsorption increases significantly. It increases when the zeolite percentage increases. The result show that the soil nitrate adsorption decreases as the irrigation event increase and soil adsorption potential degraded with irrigation events.

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In this study, the effect of clinoptilolite zeolite, as a soil amendment, on the parameters related to water and nitrogen movement in soil was investigated. Parameter and uncertainty estimation in the unamended (control) and amended soil (Z), was performed using the sequential uncertainty fitting algorithm (SUFI-2) which is linked to LEACHN (in the LEACHN-CUP software). The goodness of prediction uncertainty was judged on the basis of P-factor and R-factor. P factor, R-factor, and Nash-Sutcliffe coefficient (NS) was obtained 0.71, 0.76, and 0.92, respectively, in the prediction of the accumulated drainage from control. The results in prediction of the accumulated drainage from Z treatment using hydraulic parameters obtained in control were satisfactory (P-factor = 0.87, R-factor = 0.78, and NS = 0.87). P-factor, R factor, and NS were 0.87, 1.36, and 0.91, respectively, in the prediction of NO3-N leaching at control. According to the P-factor and R-factor values (P-factor = 1, R-factor = 2.46), application of the control parameter ranges in the prediction of NO3-N leaching at Z treatment produced a large uncertainty. By adjusting the parameters in control for zeolite amended soil, the estimated values for denitrification rate, distribution coefficient, and soil/solution NO3-N nitrification rate were greater in zeolite-amended soil compared to control.

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The conventional application of nitrogen fertilizers via irrigation is likely to be responsible for the increased nitrate concentration in groundwater of areas dominated by irrigated agriculture. This requires appropriate water and nutrient management to minimize groundwater pollution and to maximize nutrient use efficiency and production. To fulfill these requirements, drip fertigation is an important alternative. Design and operation of drip fertigation system requires understanding of nutrient leaching behavior in cases of shallow rooted crops such as potatoes, which cannot extract nutrient from lower soil depth. This study deals with neuro-fuzzy modeling of nitrate leaching from a potato field under a drip fertigation system. In the first part of the study, a two-dimensional solute transport model (HYDRUS-2D) was used to simulate nitrate leaching from a sandy soil with varying emitter discharge rates and various amounts of fertilizer. The results from the modeling were used to train and validate an adaptive network-based fuzzy inference system (ANFIS) in order to estimate nitrate leaching. Radii of clusters in ANFIS were tuned and optimized by genetic algorithm. Relative mean absolute error percentage (RMAEP) and correlation coefficient (R) between measured and obtained data from HYDRUS were 0.64 and 0.99, respectively. Results showed that ANFIS can accurately predict nitrate leaching in soil. The proposed methodology can be used to reduce the effect of uncertainties in relation to field data.

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Nowadays, due to the effective role of nitrogen fertilizer in growth, yield and crop quality, farmers apply large amount of chemical fertilizers. High application of nitrogen fertilizers has caused soil and water pollution and environmental dangers, higher nitrate accumulation in plant, and different disease risks in human and livestock. In order to investigate the effects of nitrogen and cycocel application effects on soil nitrate pollution and agronomic traits of rice, an experiment was arranged in split plot based on a completely randomized block design with three replicates at Sari region (north of Iran) in 2010. The main factor was nitrogen in four levels and cycocel was considered as a sub factor in three levels. Results showed that maximum and minimum plant height and fourth internodes bending moment were obtained in 0 and 150 kg N ha-1, respectively. Higher filled spikelet percentage per panicle, grain yield and harvest index were obtained in 100 kg N ha-1 application. Application of N up to 150 kg N ha-1 increased soil nitrate by 44.7 percent. As cycocel application decreased, the plant height and panicle length were reduced, but tiller number per plant, filled spikelet percentage per panicle, and grain yield were increased.

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To determine the nitrate pollution (water, soil, and tubers) in small (< 0.5 ha), medium (0.5- 1 ha) and large (> 1 ha) size of potato fields, this study was conducted in Fereidan region of Isfahan province during growing season of 2014-2015. For this purpose, the amounts of inputs and the tuber yield were recorded in each farm. Also, average nitrate-N concentration in irrigation water, soil and tubers of different potato farms were measured before planting and after harvesting. The results showed that the average soil N-nitrate concentration in small, medium and large size farms were 16.3, 17.4 and 19.9 mg kg^-1 before planting and 10.3, 13.3 and 23.3 mg kg^-1 after harvesting, respectively. The average N-nitrate concentration of irrigation water in small, medium and large size farms were 36.3, 27.1 and 19.5 mg L^-1 before planting and 47.6, 33.1 and 16.4 mg L^-1 after harvesting, respectively. At the post-harvest time, NO₃-N concentration of irrigation water were below the standard range concentration (45 mg L^-1) in the all large farms while 87 % of small and 85% of medium farms had more than standard concentration. The nitrate concentrations of tubers in large-sized farms were lower than others. The tuber NO₃-N concentration was affected by potato cultivar. The lowest concentration of nitrate was observed in the late-season potato cultivars (Agria). that might be associated with greater tubers yield.

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