hojjat ghorbani vaghei; M. Davari
Abstract
Introduction: Soil organic carbon (SOC) has great impacts on soil properties, soil productivity, food security, land degradation and global warming. Similar to other soil properties, SOC has a strong spatial heterogeneity as a result of dynamic interactions between parent material, climate and geological ...
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Introduction: Soil organic carbon (SOC) has great impacts on soil properties, soil productivity, food security, land degradation and global warming. Similar to other soil properties, SOC has a strong spatial heterogeneity as a result of dynamic interactions between parent material, climate and geological history, at both regional and continental scales. However, landscape attributes including slope, aspect, altitude, and land use types are dominant factors influencing on SOC in areas with the same parent materials and climate regime. Understanding and identifying the spatial and temporal distribution of SOC is essential to evaluate soil quality, agricultural management, watershed modeling and soil carbon sequestration budgets. Therefore, the objectives of this study was to estimate soil organic carbon content in the Aligodarz watershed, and to investigate the effects of altitude, slope, and land use type on SOC.
Materials and Methods: The research was carried out in the Aligodraz watershed in Lorestan province of Iran. The study area is located between latitudes N 33° 10' 51.72"to N 33° 34' 28.22" and longitudes E 49° 27' 17.99"to E 49° 58' 40.84" 14 that covers an area of 1078.9 km2. It has an altitude between 1866.3 and 3200 m above sea-level. The primary land uses within the watershed include pasture, dryland and irrigated farming. In this study, soil samples were randomly collected from 206 sites at depth of 0– 15 cm during June and August 2003. The mean distance between samples was about 5 km. Soil samples were air-dried in the shade for about 7 days and then passed through a 0.25 mm prior to determination of SOC. Soil organic carbon content was determined in triplicate for each sample using the Walkey-Black method. Basic statistical analyses for frequency distribution, normality tests, Pearson's correlation and analysis of variance were conducted using SPSS (version 18.0). Calculation of experimental variograms and modeling of spatial distribution of SOC were carried out with the geostatistical software GS+ (version 5. 1). Maps were generated by using ILWIS (version 3.3) GIS software.
Results and Discussion: The results revealed that the raw SOC data have a long tail towards higher concentrations, whereas that squareroot transformed data can be satisfactorily modelled by a normal distribution. The probability distribution of SOC appeared to be positively skewed and have a positive kurtosis. The square root transformed data showed small skewness and kurtosis, and passed the K–S normality test at a significance level of higher than 0.05. Therefore, the square root transformed data of SOC was used for analyses. The SOC concentration varied from 0.08 to 2.39%, with an arithmetic mean of 0.81% and geometric mean of 0.73%. The coefficient of variation (CV), as an index of overall variability of SOC, was 44.49%. According to the classification system presented by Nielson and Bouma (1985), a variable is moderately varying if the CV is between 10% and 100%. Therefore, the content of SOC in the Aligodarz watershed can be considered to be in moderate variability. The experimental variogram of SOC was fitted by an exponential model. The values of the range, nugget, sill, and nugget/sill ratio of the best-fitted model were 6.80 km, 0.058, 0.133, and 43.6%, respectively. The positive nugget value can be explained by sampling error, short range variability, and unexplained and inherent variability. The nugget/sill ratio of 43.6% showed a moderate spatial dependence of SOC in the study area. The parameters of the exponential smivariogram model were used for kriging method to produce a spatial distribution map of SOC in the study area. The interpolated values ranged between 0.30 and 1.40%. Southern and central parts of this study area have the highest SOC concentrations, while the northern parts have the lowest concentrations of SOC. Kriging results also showed that the major parts of the Aligodarz watershed (about 87%) have statistically SOC content less than 1%. Lower SOC concentrations were associated with high altitude (r = −0.265**). The results of Pearson correlation analysis showed that soil organic carbon content has a significantly negative correlatiton with slope gradient (r = −0.217**). The results also indicated that the SOC content was variable for the different land use types. The irrigated lands had the highest SOC concentrations, while the pasture lands had the lowest SOC values.
Conclusion: The square-root transformed data of SOC in Aligodarz watershed of Lorestan province, Iran, followed a normal distribution, with an arithmetic mean of 0.81%, and geometric mean of 0.73%. The coefficient of variation and nugget/sill ratio revealed a moderate spatial dependence of SOC in the study area. The results indicated that the major parts of the Aligodarz watershed have SOC content less than 1%. The land use type had a significant effect on the spatial variability of SOC and that lower SOC concentrations were associated with higher altitude and slope gradients. The irrigated and pasture lands had the highest and lowest SOC concentrations, respectively.
hojjat ghorbani vaghei; Hosseinali Bahrami; R. Mazhari; A. Heshmatpour
Abstract
Introduction: Maintaining soil moisture content at about field capacity and reducing water loss in near root zone plays a key role for developing soil and water management programs. Clay pot or porous pipe is a traditional sub-irrigation method and is ideal for many farms in the world’s dry land with ...
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Introduction: Maintaining soil moisture content at about field capacity and reducing water loss in near root zone plays a key role for developing soil and water management programs. Clay pot or porous pipe is a traditional sub-irrigation method and is ideal for many farms in the world’s dry land with small and medium sized farms and gardens and is still used limitedly in dry lands of India, Iran, Pakistan, the Middle East, and Latin-America. Clay capsule is one of porous pipes in sub irrigation that is able to release water in near root zone with self- regulative capacity. Watering occurs only in amounts that the plants actually need (this amount is equal to field capacity) and released water in near root zone without electricity or use of an automatic dispenser.
Materials and Methods: A study was carried out in 2013 on the experimental field of agriculture faculty of Tarbiat Modares University, to study the effect of two irrigation types on qualitative and quantitative characters in grape production (Vitis vinifera L.). In order to provide the water requirement of grape plant were used porous clay capsules for sub irrigation with height and diameter of 12 cm and 3.5 cm and dripper with Neta film type for drip irrigation, respectively. Porous clay capsules provided from soil science group at Tarbiat Modares University. In this research, the volume of water delivered to grape plants during entire growth period in two different irrigation methods was measured separately with water-meters installed at all laterals. The water consumption, yield production and water use efficiency were evaluated and compared in two drip and porous clay irrigation systems at veraison phonological stages. In the veraison stages, cluster weight, cluster length, solid solution and pH content were measured in grape fruits. Leaf chlorophyll content and leaf water content were also measured in two irrigation systems.
Results and Discussion: The results of fruit quality characteristics showed that cluster weight, cluster length, solid solution and pH content has not significant different at 5% level in two system irrigation. Also, the foliar analysis showed that chlorophyll content and relative humidity of leaf has not been affected in two irrigation systems. Meanwhile, irrigation types were significantly effect on water consumption and water use efficiency. The average water consumption and yield production with buried clay capsules and drip irrigation methods on grapevine plant were 4050 and 6668 M3.ha-1 and 14.2 and 14.8 Ton.ha-1 respectively. The reducing water consumption with buried clay capsules irrigation method in related to drip irrigation was 39% on grapevine plants. Meanwhile, the average yield production with buried clay capsules and drip irrigation methods on grapevine plant was 14.2 and 14.8 Ton.ha-1 respectively. Also, the statistics analysis show that the yield and component yield have not significant different at 5% level in the surface and subsurface irrigation. According to the water consumption and yield production, using buried porous clay capsules created a better water use efficiency than drip irrigation method. In other words, Iran has been localized at arid and semi arid and have huge water consumption in agriculture, and therefore it is necessary to optimize water consumption especially in agriculture using new technology. According to the results of this research, using buried porous clay capsules is recommended in order to optimize water consumption for grape plants in different place in arid and semi-arid regions of Iran.
Conclusion: The purpose of an efficient irrigation system is to apply the water in such a way that the largest fraction thereof is available for beneficial use by the plant. According to the experimental results reported here, it could be concluded that the reducing water consumption with buried clay capsules irrigation method in related to drip irrigation was 39% on grapevine plants. Meanwhile, the average yield production with buried clay capsules and drip irrigation methods on grapevine plant was 14.2 and 14.8 Ton.ha-1 respectively. Also, the statistics analysis show that the yield and component yield have not significant different at 5% level in the surface and subsurface irrigation. The final result, it could be concluded that the porous clay capsules have a good ability to providing water requirement of grape plant. The grape irrigation in huge area of Iran is doing with a traditional method and the authors of this work believe that porous clay capsules have a high water saving potential and good capability for irrigation of various types of crops.
Keywords: Grape plant, Porous pipe, Soil moisture, Water use efficiency, Yield
