forough fazel; Naser Ganji Khorramdel; mahdi Gheysari
Abstract
Introduction: World's population growth and limited water resources and needing to more food production led to interest farmers to use nitrogen fertilizer more than soil requires and subsequently Nitrate leaching causes groundwater and environmental pollution. Therefore, researches has concentrated ...
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Introduction: World's population growth and limited water resources and needing to more food production led to interest farmers to use nitrogen fertilizer more than soil requires and subsequently Nitrate leaching causes groundwater and environmental pollution. Therefore, researches has concentrated on improvement of nitrogen use efficiency, which numerical simulation is the effective solutions to optimize the management of water and fertilizer in the field in order to achieve the maximal yield and minimal nitrate pollution of soil, groundwater and drainage in water deficiency crisis condition. For this reason, the evaluation of new user friendly models in correct estimation of soil moisture and nitrogen content distribution and recognition of water and solutes movement in the soil and choosing the best management option for increasing productivity and economic performance and also reduction of nitrate pollution of soil and ground water source with the least limitations and high accuracy is necessary. The Eu-Rotate-N model has been developed for simulation of nitrogen use and specifically for optimization of nitrogen use in variation of vegetables in a wide range of conditions, which without the need to calibration has presented satisfactory results in many areas. So this study was conducted to evaluate the efficiency of Eu-Rate-N model in assessment of moisture and nitrogen distribution and yield under different nitrogen fertigation management for pepper plant.
Materials and Methods: Sweet pepper was planted at density of 8.33plant per m2 in a row planting method. 150kg per hectare per year of fertilizer was used during the season. Crop yield, soil water and nitrogen content were measured on a regular basis. The treatments consisted of three fertilizer level: zero (N0), the ratio of ammonium to nitrate 20:80 (N1) and 40:60 (N2), which was conducted in a completely randomized block with three replications in Isfahan. Irrigation based on daily monitoring of humidity was used with drip irrigation system. The irrigation Depth was calculated and applied with aim of replacing the water content deficiency in the root zone up to field capacity (FC) for the no water deficit treatment.
Coefficients were modified only for plant coefficients and length of each growth stage according to the area. To compare simulated data with measured data in field, indices of statistical root mean square error (RMSE), normalized root mean square error (NRMSE), coefficient of determination (r2) and index of agreement Wilmot (d) were used.
Results and Discussion: The NRMSE index for nitrate and soil water content was 11.45, 12.08, the RMSE was 0.89, 0.022, the r2 was 0.998, 0.996 and the d was 0.667, 0.66 respectively. All calculated indices for soil water and nitrate content were in the acceptable range. NRMSE index was less than 20 percent in all treatments which was indicating good ability of model in simulating soil water and nitrate content and r2 was more than 90 percent which pointed out to well process of simulation of the model. The simulation accuracy was greater at the end of the growing season. Comparing of RMSE statistical index for different depths showed that the simulation accuracy was increased by increasing depth which can be due to changes in surface evaporation and also the effect of environmental factors on surficial layers more than other layers. Generally the best simulation was related to the layer of 80 to 100 cm. And the average RMSE was 0.019 cm3 per cm3 for soil moisture content and 0.22 mg per kg for soil nitrate.In the layer of 80-100 cm the best simulation of soil moisture and nitrate content between treatments was related to N0 by the RMSE equal to 0.024 cm3 per cm3 and 0.21 mg per kg respectively and the weakest simulation was related to N3.The simulated yield in all treatments was less than its actual value. Comparison of simulations between three treatments demonstrated the usefulness of EU-Rotate N to examine the effects of management on, nitrate leaching.
Conclusions: The Eu-rotate-n model without calibration for site location was well capable of estimating soil water and nitrate content under different fertilizer management for Isfahan climatic conditions nevertheless it is suggested to use to calibrate yield functions to improve the yield simulation. Generally we can use Eu-rotate-n model for simulation of water and nitrogen content and eventually approach to integrated and optimal management in the farm in the hot, dry conditions of Isfahan.
M. Gheysari; M.M. Majidi; seyed majid mirlatifi; M.J. Zareian; S. Amiri; S.M. Banifatemeh
Abstract
The response of root to water stress is one of the most important parameters for researchers. Study of growth and distribution of root under different irrigation managements helpsresearchersto a better understanding of soil water content, and the availability of water and nutrition in water stress condition. ...
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The response of root to water stress is one of the most important parameters for researchers. Study of growth and distribution of root under different irrigation managements helpsresearchersto a better understanding of soil water content, and the availability of water and nutrition in water stress condition. To investigate the effects of four levels of irrigation under two different deficit irrigation managements on the root length of maize, a study was conducted in 2009. Irrigation managements included fixed irrigation interval-variable irrigation depth (M1) and variable irrigation interval-fixed irrigation depth (M2). Maize plants were planted in 120 large 110-liter containers in a strip-plot design in a randomized complete block with three replications. Root data sampling was done after root washing in five growth stages. The results showed that the effect of irrigation levels on root length was significant (P
N. Ashrafi; M. Gheysari; A. Maleki; A. Nikbakht
Abstract
Introduction: Olive (Olea europaea L.) trees are mainly cultivated in the Mediterranean area and are grown for their oil or processed as table olives. Despite the fact that olive is known to be resistant to drought conditions due to its anatomical, physiological, and biochemical adaptations to drought ...
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Introduction: Olive (Olea europaea L.) trees are mainly cultivated in the Mediterranean area and are grown for their oil or processed as table olives. Despite the fact that olive is known to be resistant to drought conditions due to its anatomical, physiological, and biochemical adaptations to drought stress, reports indicate that the olive can be adversely affected by drought stress, which has a negative effect on the growth of olive trees. In the absence of adequate supplies of water, the demand for water can be met by using improved irrigation methods or by using reclaimed water (RW). Reports have shown that recycled water has been used successfully for irrigating olive orchards with no negative effects on plant growth.Attention has been paid to reclaimed water as one of the most significant available water resources used in agriculture around large cities in arid and semi-arid regions. On the other hand, irrigation efficiency is low and does not meet the demands of farmers.In order to investigate the possibility of irrigating olive orchards with subsurface leakage irrigation (SLI) in application of reclaimed water, an experiment was carried out with the aim of investigating the effect of reclaimed water on photosynthetic indices and morphological properties of olive fruit.
Materials and Methods: Research was conducted using a split-plot experimental design with two factors (irrigation system and water quality) on the campus of Isfahan University of Technology in Isfahan, Iran, on a sandy-clay soil with a pH of 7.5 and electrical conductivity (EC) of 2.48 dSm-1.PVC leaky tubes were used for the SLI system. The SLI system was installed 40 cm from the crown of each tree at a depth of 30 - 40 cm.At the end of the experiment fruit yield, weight per fruit, volume, length and firmness were calculated. A portable gas exchange system (Li-6400., LICOR, Lincoln, NE, USA) was used to measure the net rate photosynthesis (A), the internal partial pressure CO2 (Ci), and stomatal conductance (gs) between (09.30 – 11.30 h) on a fully expanded current season leaves situated at mid canopy height. Statistical assessments of differences between mean values were performed by the LSD test at P = 0.05.
Results and Discussion The results revealed that reclaimed water enhanced fruit yield, weight (15%), volume (23%) and leaf photosynthesis (22%) in plants compared with clear water. Recycled water was found to supply more nutrients than clear water. High nutrient concentrations in RW, compared to those in clear water, result in nutrient accumulation in the soil, making them available to plant roots to promote overall plant growth and fruit production. Improved N, P, K nutrition of wastewater-irrigated plants has been reported (Farooq et al, 2006). Olive leaves and stems represent storage organs for N and release it in response to the metabolic demands of developing reproductive and vegetative organs (Fernandez-Escobar et al., 2004). However, Al-Abasi et al. (2009) found no statistical differences. Irrigation with SLI systems increased the photosynthesis (33%), and stomatal conductance (57%) when compared with surface irrigation systems. The results showed that reclaimed water had a significant effect on photosynthesis and stomatal conductance. However, fruit length and firmness had no significant difference. Substomatal CO2 decreased when the SI systems were used for irrigation. Also SLI system could enhance fruit yield (65%), weight (17%), photosynthesis (32%) and chlorophyll Fluorescence (Fv/Fm) (18%). The SLI systems with recycled water induced greater shoot growth, total leaf surface area, and transpiration during the entire growing period. This led to an overall positive effect on mean fruit weight and total fruit production per tree. The SLI system applying RW led to more photosynthesis by 34% as compared to the SI system. In the present study, the SLI system delivered water directly in the root zone and improved water availability, which enhanced photosynthetic assimilation rates and plant growth to a great extent. David et al. (2003) showed that subsurface drip irrigation versus other irrigation methods reduced evaporation and improved growth and production in peach trees.
Conclusion: As a conclusion, the results from this research show that recycled water could be a promising resource for irrigation of olive trees and acted as a source of nutrients and irrigation water.In addition, SLI irrigation system is more efficient in irrigation of olive trees when compared to surface irrigation system and proved beneficial for olive growth.
