JWSS - Journal of Water and Soil Science

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To evaluate the effect of nitrogen slowly released from pellet, composed of manure and urea fertilizer on the Nitrogen efficiency and morphological Characteristics and grain yield of corn hybrid (S.C704), a field experiment was carried out in Aboureihan research farm of Tehran University in 2009. The factorial design of the study comprised a randomized complete block with three replications. The application rates of N at four levels (46, 92, 138 and 184 kg N. ha-1) and two levels by methods of N distribution (pellet and mixed with soil) were applied. In this research, a Screw Extruder setup was designed and manufactured. Statistical analysis indicated that NUE, as well as agronomic efficiency (AE) was reduced while physiological efficiency (PE) increased with increasing N rates. Also, most plant length and stem diagonal and cob diagonal pellet belonged to the treatment. But, the number of leaves per plant did not affect the distribution method of fertilizer.The results showed significant differences among various rates of nitrogen and methods of N distribution considering grain yield and grain protein. The higher rates of N increased grain protein, grain yield and yield components (except for number of rows per ear). Maximum grain yield (11.1 t. ha-1) was obtained with 184 kg N. Ha-1 treatment.

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Effect of urban sewage and nitrogen on soil chemical characteristics in sweet corn was evaluated in Yasouj region at 2009. Five irrigation treatments were managed common water during entire period of growing season as control (I1) urban sewage during the first half of growing season (I2) urban sewage during the second half of growing season (I3) alternate urban sewage and common water (I4) and urban sewage during entire period of growing season (I5) and three nitrogen rates (N0=0, N80= 80 and N160=160 kg N ha-1) in a completely randomized design with three replications. Results indicated that the soil N, P and K concentrations in treatment I5 had a significant difference compared to the other irrigation treatments. Irrigation levels were also exhibited a significant difference in soil organic matter and EC. Maximum and minimum of soil organic matter were observed in I5 (%0.45) and in I1 (%0.33), respectively. Maximum and minimum of soil EC were found in I5 (2.0 dsm-1) and in I1 (1.4 dsm-1), respectively. Irrigation treatments did not show a significant change in soil pH. The effect of irrigation and interaction between irrigation treatments and nitrogen rates were not significant on available forms of Fe, Zn, Cu and Mn in soil. The effect of nitrogen fertilizer was significant on soil N content. Maximum (%0.034) and minimum (%0.030) of soil nitrogen were noticed in N160 and N0, respectively.

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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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In order to evaluate the effect of concentration and time of foliar spraying of nitrogen fertilizer as supplemenfary to soil nutrition on grain yield and some important traits of rapeseed (Hyola401), an experiment was conducted in complete randomized block design with 16 treatments and three replications in in 2008-2009, 2009-2010 growing seasons, and in 2003-2005 growing seasons in paddy fields of Rice Research Institute of Iran (Rasht). In this experiment, nitrogen concentration (from urea source) at two levels (5 and 100.00) and application time at seven levels including 1-seedling stage: 6-8 leaves 2: beginning of stem elongation 3: prior to flowering 4: 6-8 leaves + stem elongation 5: 6-8 leaves + prior to flowering 6: stem elongation+ prior to flowering 7: 6-8 leaves + stem elongation+ prior to flowering with two control treatments including zero nitrogen fertilizer and basal fertilization as 1/3 at seed sowing, 1/3 at stem elongation and 1/3 prior to flowering stages of 180 kg pure N ha were considered. Results of combined analysis showed significant differences between the experimental treatments in most traits. Spray application of nitrogen (100.00) in stem elongation+prior to flowering stage produced maximum silique length (6.8 cm), number of secondary branch (7.1) and plant height (141.1 cm). Also, the spray application (100.00) in 6-8 leaves+stem elongation+ prior to flowering stage had maximum biological yield (10684.6 kg.ha-1), grain and oil yields (3686.2 and 1489.3 kg.ha-1, respectively) and the maturity period (202 days). Spray application (100.00) in stem elongation+ prior to flowering stage did not induce significant difference with spray application (100.00) in the three stages. Maximum oil content was observed in control treatment (zero nitrogen fertilizer) with an average of (44 %). According to the results of the present experiment, it seems that spray application of nitrogen (100.00) at final growth stage of rapeseed (stem elongation+ prior to flowering stage) increases grain and oil yields.

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A study was conducted to evaluate the effect of vermicompost and nitrogen (N) on growth, nutrient concentration and uptake of N, phosphorus (P), potassium (K), iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) in sunflower shoots as a factorial experiment arranged in completely randomized design (CRD) with three replications under greenhouse conditions. Treatments included three levels of vermicompost (0, 2.5, and 5 % by w/w) and three N levels (0, 90, and 180 mg kg-1) as urea. Application of 2.5% vermicompost significantly increased the average fresh and dry weights, and uptake of K, Fe, Zn, Mn, and Cu of shoots as compared when no vermicompost was applied, but decreased Zn and Cu concentrations. Application of 90 mg N, increased fresh and dry weights, and concentration of N, Zn, and Mn, total uptake of N, P, K, Fe, Zn, Mn, and Cu in sunflower shoots, but decreased P concentration. Application of 180 mg N increased total N uptake than that of 90 mg N kg-1 treatment. Combination of 2.5% vermicompost with 90 mg N, significantly (p<0.05) increased dry matter yield of sunflower as compared to 2.5% vermicompost without N treatment

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Evaluation of chemical and biological indicators of soil in different land uses could be helpful in sustainable range management, preventing degradation of soil quality trend. This study was conducted in Friedan in Isfahan province in 2010 to compare chemical and biological indicators in three land uses (rangeland, degraded dry land and dry land), during two growing seasons (May and September) in three slopes (0-10, 10-20, 20-30 %). Nitrogen, phosphorus, potassium, organic matter, cation exchange capacity and microbial soil respiration were measured. Results showed that all measured characteristics except potassium decreased over an increase in the slope. Maximum values of phosphorus, organic matters, cation exchange capacity and soil respiration were obtained in pasture (28.4 mg/kg, 0.62%, 20.38 cmol/kg, 33.2 mgC/day, respectively)but potassium maximum rate was seen in dry land form (406.8 mg/kg).The effect of season on all measured parameters was significant except for N, while the highest amounts of phosphorus, potassium, cation exchange capacity and soil respiration (28.7 mg/kg, 377.3 mg/kg, 19.6 cmol/kg and 25.9 mgC/day, respectively) were seen in May and the highest organic matter rate (0.68%)in September. The results of this study showed that an increase in the slope, poor range management, and the end of the growing season could be major factors degrading the soil quality indices and soil productivity.

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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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Salinity and nutrient deficiency particularly nitrogen are two important limiting factors for yield production in arid and semi-arid regions. The objective of this study was to model basil response to combined salinity and nitrogen deficiency. To that end, modified Leibig-Sprengel (LS) and modified Mitcherlich-Baule (MB) and also some newly derived models based on combination of MB with salinity models of Maas and Hoffman (31), van Genuchten and Hoffman (36), Dirksen and Augustijn (17) and Homaee et al., (23) were evaluated. The experiment was conducted under four salinities including 1.175, 3, 5, and 8 dSm^-1 and four nitrogen levels including 100, 75, 50, and 0 percent of fertilizer requirements each with three replicates. Results indicated that from among the evaluated models, the derived models of MB and Maas and Hoffman (MB-MH) (nRMSE=4.9), MB and van Genuchten and Hoffman (MB-VG) (nRMSE=5.4), and also MB and Homaee et al., (MB-H) (nRMSE=7.0) provide best fits to the measured data. Also, the comparison of two modified LS and MB models indicated that the estimated relative yield for irrigation water salinity levels by modified LS model (nRMSE=4.6) provides better results (nRMSE=5.9). However, for soil nitrogen levels and interactive effects of salinity and nitrogen, the modified MB model (nRMSE=10.3) provided better outputs (nRMSE=14.4). Consequently, instead of the modified LS and MB models the proposed models in this research can be recommended for use.

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Earthworms are an important component of soil fauna because of their fundamental impact on soil physical, chemical and biological properties. To evaluate the effects of earthworms on some soil chemical properties as well as plant growth indicators, an experiment was carried out in a completely randomized design in greenhouse conditions. The first factor involved the presence or absence of earthworms (Eisenia foetida), the second factor was different organic matter including control (no organic materials), pruning waste compost of apple and grape (PWC), wheat straw (WS), Herbal extracts waste (HE), pruning waste (PW) and the third factor was the presence or absence of corn plant for evaluating rhizosphere soil. At the end of growing period, some soil chemical properties including total nitrogen, organic carbon, ammonium, nitrate and plant growth indicators were measured. The results showed that application of organic matter and earthworm inoculation had significant effects on soil chemical properties. The pruning waste compost (PWC) treatment showed the largest impact on ammonium and nitrate content (1.7 and 3.3 times compared to control treatment, respectively). In pruning waste compost (PWC) treatment, organic carbon amount in rhizospheric soil increased from 0.9 at non-rhizosphere to 1.32 %. The presence of earthworm improved plant growth parameters including shoot and root dry weight by 34% and 30%, respectively, compared to earthworm absence condition. Soil ammonium and nitrate contents at earthworm presence increased 32% and 49%, respectively. Therefore, application of organic matter with earthworm inoculation had better results in comparison with no earthworm inoculation.

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Chemical fertilizers have important role in modern agriculture, and in the other hand led to rigid environmental pollution. Urea fertilizer is one of the most widely used and least expensive nitrogen fertilizers in Iran. Since it is high solubility in water a significant of it, if irrigation or precipitation is heavy, easily washed and led to change to change the quality of groundwater, rivers or seas. Hence, in this study the effects of deficit irrigation and fertilization on pollution using SWAT for Tashk-Bakhtegan basin (land area between Dorudzan dam and Khan Bridge) were simulated. This model by comparing model outputs with actual observations of hydrological, crop yield (wheat, barely, corn and rice) and nitrate by using SUFI2 algorithm in SWAT_CUP software were calibrated and validated. Then the calibrated model used to evaluate different management strategies (e.g. irrigation and fertilizer amount). When the impacts of different levels of urea (0 to 70 percent reduction in urea application) were modeled, yield of these crops reduced between 1 to 27, 0.8 to 24, 0.42 to 21 and 0.47 to 9 percent for wheat, barely, corn and rice, respectively. However, these tends to decline nitrate leaching 16-81, 18-80, 15-85 and 12.5 to 83.6 percent, respectively for these crops.  Therefore, by comparing yield and nitrogen loss changes, this result can conclude that a significant reduction in nitrogen loss by minimum cost on yield can achieved by optimize fertilizer application. 

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In this research, a comprehensive simulation model for water cycle and the nitrogen dynamics modeling including all the important processes involved in nitrogen transformations such as fertilizer dissolution, nitrification, denitrification, ammonium volatilization, mineralization, immobilization as well as all the important nitrogen transportation processes including nitrogen uptake by the plant, soil particles adsorption, upward flux, surface runoff losses and drain losses, was used for fertilizer management modeling in a sugarcane farmland in Imam Khomeini Agro-Industrial Company using a system dynamics approach. For evaluating the model the data collected from Imam Agro-Industrial Company equipped with a tile drainage system with shallow ground water and located in Khuzestan province, Iran, were used. The statistical analysis of the observed and simulated data showed that the RMSE for determining the accuracy of simulation of the nitrate and ammonium concentration in drainage water is 1.73 mg/L and 0.48 mg/L, respectively. The results indicated that there is good agreement between the observed and the simulated data. Nine scenarios of fertilization at different levels of urea fertilizer were modeled including one scenario of 400 kg/ha, two spilit scenarios of 350 kg/ha, two spilit scenarios of 325 kg/ha, two spilit scenarios of 300 kg/ha, one scenario of 280 kg/ha and one scenario of 210 kg/ha. Results of the modeling showed that the scenario of 210 kg/ha has the highest nitrogen use efficiency (52.3%) and the lowest nitrogen losses consisted of denitrification, ammonium volatilization and drainage losses (17.82, 7.16 and 92.59 kg/ha, respectively). The results revealed that increasing the consumption of urea fertilizer greater than 210 kg/ha increased the overall nitrogen losses and reduced the nitrogen use efficiency. Meanwhile, this model can be used for managing the fertilizer and controlling the nitrate and ammonium concentrations in the drainage water to prevent the environmental pollution. Also, the system dynamics approach was found as an effective technique for simulating the complex water-soil-plant-drainage system.

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Nitrogen use efficiency is relatively low in irrigated rice fields because of rapid N losses from ammonia volatilization, the nitrification, surface runoff, and leaching in the soil-flood water system. Since the plant N represents the total N supply of all sources, plant N status will be a good indicator of N availability to crops at any given time. Leaf colour chart (LCC) is a simple portable diagnostic tool, to determine the timing of N top dressing. LCC was developed to increase the N use efficiency at irrigated rice fields. A field experiment was carried out to compare the effect of N split application and LCC on the grain yield and agronomic and recovery efficiency of Fajr variety in 2009. The experiment was conducted in a randomized complete block design with 12 treatments in 3 replications on Fajr cultivar. Twelve treatments included control treatments (without nitrogen fertilizer) and 45, 90, 135 kg N ha^-1 for three times each and two treatments included LCC treatments 4 and 5. As a result, all treatments showed significant (p=0.05) grain yield increase in comparison to control. Increased yield was observed up to 135 kgN/ha (55.2%). Grain yield of LCC treatments was higher than split treatments. LCC treatment 5 had higher AE, RE, PE, PFP and IE than LCC 4 and fixed – 135 at the less N rate in all fields. Therefore, the results of different fertilizer treatments showed that the LCC treatment 5 with maximum grain yield, agronomic, physiological, internal and relative efficiency factors can be considered as the best management method for using nitrogen fertilizer and preventing from excess use of nitrogen fertilizer in Fajr cultivar. 
 

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The Firing effect on soil depends on its intensity and duration. In order to investigate influence of different firing backgrounds on some soil physical and chemical properties, 80 soil samples were taken from two depths (0-5 cm and 5-20 cm) with different time of firing background (2 and 12 months). Some soil physical and chemical characteristics were measured at soil samples. The results showed that there was a significant difference in the amount of pH, EC, bulk density and ammonium in soils with different history of burning. The amount of studied indices increased after firing in burned soils compared to the control ones. However 12 months later they reach to their pre-fire levels. Total nitrogen amount in soils with 2 and 12 months firing history were 1.18 and 1.11 times higher than the control soils, respectively. The amount of organic carbon in surface depth (0-5 cm) of burned soils with 2 and 12 month firing backgrounds 37.25 and 24.7 percent increased in comparison to control soils, respectively. Also, fire led to a significant reduction in the amount of clay (29.25 percent) in burned areas compared to the control ones. Soil particle size distribution in control sites were in clay up to loam and in burned areas were in clay loam up to sandy loam classes. Therefore forest firing causes obvious changes in soil properties, remediation of which takes more than one year.
 

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This study was conducted based on a randomized complete block design and a factorial experiment with three replications in regions to investigate the effect of different rates and times of nitrogen on the quantitative properties of safflower. The first factor was different nitrogen rates including 0, 60, 120 and 180 kg ha^-1 , and the  second one was nitrogen application time including seed sowing, rosette and the before flowering stage; these were  1-0-0, 1/3-2/3-0, 2/3-1/3-0 and 1/3-1/3-1/3 with the  Goldasht variety. The results showed that nitrogen rate had a significant effect on all studied traits. Nitrogen application time also had a significant effect on capitulum number and yield at p>0.99 and on the length of plant, nitrogen adsorption, agronomic efficiency and apparent recovery at p>0.95. So based on the results, the recommended consumption of 60 kg/ha N was split into three equal amounts at the time of planting, rosette and flowering or 1/3-2/3-0, in Kerman area.

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