ali ataee; Mehdi Akbari; Mohammadreza Neyshabouri; zahra ghaffari; Davood Zarehaghi
Abstract
To investigate the effects of substituting surface drip irrigation (DI) by subsurface drip-irrigation systems (SDI) on plant responses, a10 ha pistachio orchard with DI system located in Shahriar, Tehran province, was selected. Irrigation treatments including DI and SDI with saline water and DI with ...
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To investigate the effects of substituting surface drip irrigation (DI) by subsurface drip-irrigation systems (SDI) on plant responses, a10 ha pistachio orchard with DI system located in Shahriar, Tehran province, was selected. Irrigation treatments including DI and SDI with saline water and DI with non-saline water (A) were established and plant responses were measured. The salinity distribution results showed that, in DI, at depth of 30-50 cm and distance of 70-100 cm, salts were accumulated. In SDI, salt accumulation was observed in surface layer and in distance of 60-80 cm from the tree. Based on all plant response indicators, treatment A showed significantly more favorable conditions. Unlike treatment A, there was no significant difference in the “canopy temperature” and “canopy–air temperature difference” between DI and SDI. By normalization of environmental-effects on foliage temperature, crop water stress index (CWSI) showed significant differences between DI and SDI treatments. Also, stomata conductance in SDI was significantly greater than DI. Additionally, treatment A had significantly the highest sap flow (SF). Based on SF measurement in 24 hour, there were no significant differences between DI and SDI irrigation systems, but the mean of this index for daylight time and midday, showed significant differences. With equal depth of irrigation water applied to DI and SDI and more favorable salinity distribution in root zone of SDI, this treatment leads to less water and salinity stress. Although the use of subsurface drip irrigation system requires long-term studies, but in view of the observed plant responses and in terms of soil salinity distribution, it is recommended to use SDI in pistachio trees.
ali ataee; Mohammadreza Neyshaboori; Mehdi Akbari; Davood Zare haghi; Ajdar Onnabi Milani
Abstract
Multidimensional nature of water flow, plant uptake, and high frequency of water application increase the complexity in modeling soil moisture dynamics from trickle irrigation. By determining soil hydraulic properties, parameters of root distribution model for pistachio trees in the field, evapotranspiration ...
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Multidimensional nature of water flow, plant uptake, and high frequency of water application increase the complexity in modeling soil moisture dynamics from trickle irrigation. By determining soil hydraulic properties, parameters of root distribution model for pistachio trees in the field, evapotranspiration and inflow flux, soil moisture distribution was modeled using HYDRUS-2D model for surface (DI) and sub-surface drip irrigation (SDI) systems. Also, soil moisture content in the following days after irrigation was measured at different lateral and vertical distances from the tree by using Moisture Meter Profile Probe. Leaf stomatal conductance was used to test the model and parameterize water-stress response function. The h50 for pistachio tree, which represents the pressure head at which the water extraction rate is reduced by 50%, was calculated 4935 cm. HYDRUS outputs were compared with measured data in corresponding locations, and values ofME, RMSE, E and R2 statistics were obtained -0.002, 0.02, 0.7, 0.741 for DI and 0.006, 0.021, 0.761, and 0.794 for SDI respectively. The calculated transpiration by HYDRUS showed high correlation with stomatal conductance, especially in SDI. Based on plant measurements and HYDRUS results, root water uptake in SDI was significantly more than DI. Therefore, using SDI systems, by decreasing evaporation, saves more water and increases irrigation efficiency. The calculated root water uptake and measured stomatal conductance for the pistachio trees revealed that soil moisture perfectly supports plants until four days after irrigation. Thus, by decreasing irrigation interval in the field, maximum potential of drip irrigation systems can be achieved.
a o; m n; m m; d z
Abstract
Large areas of Iran are affected by salinity and drought. Due to the tolerance of almond (Prunus dulcis) to water stress, this tree is mainly grown in arid and semi-arid regions, where salinity is commonly another agricultural problem at such areas. Sensitivity of almond trees to salinity calls for special ...
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Large areas of Iran are affected by salinity and drought. Due to the tolerance of almond (Prunus dulcis) to water stress, this tree is mainly grown in arid and semi-arid regions, where salinity is commonly another agricultural problem at such areas. Sensitivity of almond trees to salinity calls for special attention to the integrated effect of salinity and water stress on its water relations. This study aimed to evaluate the combined effect of salinity and drought stress on almond water status. The trial was conducted during 2014 based on randomized complete block design with three replications on a loamy sand soil at horticultural station of the Agricultural Research Center of Azarbaijan province. Treatments comprised three irrigation salinity levels viz. 2 (T1), 4 (T2), and 5 (T3) dSm-1. Leaf (Tc) and air (Ta) temperatures, air relative humidity, leaf water potential (LWP) and integrated volumetric soil water content (SWC) at three depths (0˗20, 0˗40, and 0˗70) were measured at midday (12˗14) during the growing season. Results indicated that salinity had significant effect (p<0.0001) on stomatal conductance (gs), Tc, LWP and available water depletion (AWD). Seasonal averages of gs for treatment T1 to T3 were 0.86, 0.59 and 0.44 cm.s-1, respectively, and the corresponding LWP were ˗1.90, ˗1.93 and ˗2.16 MPa. Also, significant correlation was found between gs, LWP, Tc and AWD. Based on the regression equations, threshold value of gs for initiating stress was obtained to be 0.73 cm s-1. Corresponding LWP and AWD for this gs value were ˗1.85 MPa and 64%, respectively. Optimum Tcfor highest gs was determined to be 28.2 oC. Highly significant correlation between Tc and other water status indicators showed that midday canopy temperature may be a useful tool for assessment of water status and irrigation scheduling of almond orchards.
A RASOULZADEH; S RAZAVI; M.R NEYSHABOORI
Abstract
Saturated hydraulic conductivity is one of the main soil physical properties used in the modeling of water and solute transport and management of irrigation and drainage problems. Laboratory and field methods for direct measurement of this property are time consuming and costly. Thus, indirect methods, ...
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Saturated hydraulic conductivity is one of the main soil physical properties used in the modeling of water and solute transport and management of irrigation and drainage problems. Laboratory and field methods for direct measurement of this property are time consuming and costly. Thus, indirect methods, such as pedotransfer functions, have been developed to estimate this property. The objective of this study was evaluation of regression-based pedotransfer functions, Rosetta pedotransfer function with artificial neural network approach, and fractal models to estimate saturated hydraulic conductivity. In addition, due to the importance and role of preferential flow of water and chemicals in the soil medium, hydraulic conductivity of large pores was estimated using fractal model. To do so, 31 soil samples with different soil textures and measured saturated hydraulic conductivity by falling head method were selected. Easily measured soil physical properties, such as particle size distribution, bulk density, particle density, and organic matter content were determined in laboratory. Saturated hydraulic conductivity was estimated using the aforementioned models and the measured soil physical properties. For the purpose of comparison and evaluation of pedotransfer functions, fractal model, statistical criteria e.g., deviation time (DT), geometric mean error ratio (GMER) and geometric standard deviation error ratio (GSDER) were calculated for all the models. Results showed that the Wosten et al. and Campbell-Shiozawa models were, respectively, the best and worst estimator of matrix saturated hydraulic conductivity. The statistical criteria indicated that the adjusted fractal model in this study showed the best estimation of macropores saturated hydraulic conductivity.