M. Mohajerpour; A. Alizadeh; Mohammad Mousavi baygi
Abstract
Interception is one of the important and effective parameters on ET and hydrological relation, which is ignored in many situations. In order to investigate the effectiveness of LAI and extinction coefficient on amount of interception, in this study wheat and soybean were cultivated in thelysimeters of ...
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Interception is one of the important and effective parameters on ET and hydrological relation, which is ignored in many situations. In order to investigate the effectiveness of LAI and extinction coefficient on amount of interception, in this study wheat and soybean were cultivated in thelysimeters of agricultural school of Fredowsi Uni. of Mashhad, in Spring and Summer 2012 in the same treatments. The results showed that there is relationship between interception and LAI and extinction coefficient. By increasing LAI, interception increased significantly (slope 0.15). The maximum amount of interception was 1.19 cm in soybean by 6.19 LAI and in wheat cultivars was 1.1cm in 4.58LAI. Also by decreasing the extinction coefficient, interception increased by the rate of 1.023. Results showed that in the same LAI (3.2), wheat interception was more than soybean, 0.74 and 0.5 respectively. While in the same extinction coefficient interceptions was the same in two crops. Standardization the amount of interception by LAI, showed that the effect of the crop on interception is still remained, while by standardize the interception by extinction coefficient, the influence of crop on standard interception removed. The obtained result showed that the type of crop has a significant effect on interception, which can be shown by extinction coefficient.
nona sheikholeslami
Abstract
Evapotranspiration is one of the most important parameters that its understanding is necessary for estimating crop water requirement and design of irrigation systems. This phenomenon is greatly influenced by climatic parameters. In this study, the relative importance of variables affecting this phenomenon ...
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Evapotranspiration is one of the most important parameters that its understanding is necessary for estimating crop water requirement and design of irrigation systems. This phenomenon is greatly influenced by climatic parameters. In this study, the relative importance of variables affecting this phenomenon was evaluated and the reference evapotranspiration was estimated using principal component analysis and factor analysis. Daily scaled measurements for the period of 1991-2005 were obtained from synoptic stations located in Mashhad Khorasan Razavi provience, Iran. Mashhad has a semi-arid climate area. The measurements included the relative influence of temperature (T) (maximum, average and minimum), relative humidity (RH), sunshine hours (Rs), and the wind speed at a height of two meters above the ground (U2). The multiple linear regressions were used to estimate evapotranspiration. T-statistic with a significant level of 5% was used for the main components. The evapotranspiration was correlated more with T (minimum. maximum, and average), and relative humidity as than wind speed or sunshine. PC1 had more effect than PC2 (with coefficients of 0.694 and 0.556, respectively). MLR-PCA and MLR with coefficients of 0.903 and 0.897 (respectively) indicated higher ability for PCA method.
H. Emami; A. Lakzian; M. Mohagerpour
Abstract
Abstract
Different definitions have been proposed for soil quality. Various soil properties have been suggetsted as soil quality indices by researchers. This research was conducted to study the relationship between slope of retention curve at its inflection point (S index) and other soil physical quality ...
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Abstract
Different definitions have been proposed for soil quality. Various soil properties have been suggetsted as soil quality indices by researchers. This research was conducted to study the relationship between slope of retention curve at its inflection point (S index) and other soil physical quality indices, because the reserches between S index and soil physical properties are little. Thirty five soil samples were collected and some physical and chemical properties measured . The moisture contents were measured at 0, 1.5, 2.5, 5.5, 10, 20, 30, 50, 100, 200, 300, 500, 1000 kpa pressure heads. The parameters of Van Genuchten equation (1980) were determined by using of RETC software. The slope of retention curve at the inflection point were determined and it was considered as soil physical quality index (S). Then the relationship between S index and soil physical properties was determined by SPSS software. According to the S index and penetration resistance (PR), It seems that the physical quality of studied soil samples was suitable for accesssing. Also there was a significant correlation between S index with mean weight diameter (MWD), clay percentage, sodium absorption ratio (SAR), organic matter percentage, electrical conductivity (EC), least limiting water range (LLWR), available water content (AWC), and penetration resistance (p