Mehdi Naderi Khorasgani; Ghasem Haj Hassani; Jahangard Mohammadi; Ahmad Karimi
Abstract
The Effect of Different Tillage Instruments on Some Soil Physical Characteristics and Soil TranslocationIntroductionTillage is defined as disturbing the soil and changing soil physical condition of seedbed and root zone and making it suitable for cultivation. Soil physical characteristics like soil moisture ...
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The Effect of Different Tillage Instruments on Some Soil Physical Characteristics and Soil TranslocationIntroductionTillage is defined as disturbing the soil and changing soil physical condition of seedbed and root zone and making it suitable for cultivation. Soil physical characteristics like soil moisture and temperature conduction, bulk density, porosity and particle size are changed in the following of soil tillage. Tillage also increases water infiltration rate and plays an important role in soil moisture protection and decreasing flood hazards in arid and semi-arid regions. Molboard plough is currently implemented for tillage in different parts of Iran including Chaharmahal va Bakhtiari province. There are evidences which show Moldboard plough triggers physical soil characteristics deterioration and soil tillage erosion. Tillage translocation coefficient, as a component of tillage erosion, is defined as the amount of soil transition for 1 m width of tillage instrument. Comparing the impacts of available tillage instruments on physical soil characteristics, soil transition and their efficiency with of Moldboard plough may encourage field managers to substitute other instruments with Moldboard plough. This research aimed to: 1) study the impacts of the currently available tillage instruments (Moldboard, Disk and Chisel plough) on some prominent physical soil characteristics and 2) compare soil translocation coefficients of the mentioned tillage instruments. Materials and Methods This research was executed in Research-Training Field of Shahrekord University, Shahrekord county, Chaharmahal va Bakhtiari Province, Iran. A split plot experimental design with complete randomize block was considered with 3 major treatments of tillage instruments (Molboard, Disk and Chisel plough), minor treatments of slope (0, 3, 6 and 8%) and tillage speeds (2, 5, and 8 km h-1) and 3 replications. The conventional tillage depth of 25 cm was adjusted for all three tillage instruments. Standard protocols were applied and soil electrical conductivity (EC), pH, calcium carbonate equivalent (CCE), organic matter and soil texture components were measured before tillage application and soil field capacity (FC), mean weight diameter (MWD) of aggregates, geometric mean diameter (GMD) of aggregates, aeration porosity (Fa), bulk density (ρb) and water stable aggregates (WSA) were measured using standard protocols after tillage implementations. Colored gypsum cylinders were used as indicators for detecting soil translocation. The transition distance of the colored gypsum cylinders of each layer of tillage depth (0-9, 9-18 and 18-25 cm) was measured using tape meter or ruler and mean transition for each layer were calculated. In the next step the depth weight soil translocation was calculated for each tillage instrument. Results and Discussions Chemical analysis of soil samples showed that soils were non-saline, soil OM content was less than 1% and CCE of soil samples was relatively high. Physical soil analysis of soil samples before tillage implementation indicated that there was not any restriction for plant root development and aeration as ρb was relatively low and aeration porosity was 10% <, respectively. Analysis of variance (ANOVA) indicated that the effects of tillage type on MWD and ρb were significant (P < 0.05). Comparing the means of MWD and ρb induced by tillage instruments (Duncan method) revealed significantly higher values of MWD and lower values of ρb for soils which were treated by MB plough, the results were corresponded to the finding of other researchers. There were not significant differences between MWD and ρb of soils which were treated by disk and chisel plough. The results also showed that tillage instruments did not impact on physical characteristics like FC, WSA, GMD and FA. Non-significant impact of MB plough on soil moisture condition also was reported by other researchers in the northwest of Iran. The ANOVA was calculated for soil translocation and showed that the effects of tillage instruments were significant (P < 0.05) for all three layers of soil depth. Mean soil translocation of surficial layer of tillage depth (0-9 cm) was significantly higher than of other layers of tillage depth. Despite other researchers' findings, our research indicated that the slope levels were not significant for soil translocation. This research also revealed that tillage speed significantly (P < 0.05) impacted on soil translocation which was corresponded to findings of other researches in different parts of the world. Interaction of slope-speed and tillage type-speed were significant (P < 0.05) which could be due to accelerated impacts of speed on soil translocation in steep areas. Amount of coefficient of translocation for MB plough was 141 kg m-1 per application. This value was about one third of soil translocation which was reported by others from Belgium (545 kg m-1 y-1) or Denmark (456 kg m-1 y-1) and very closed to the finding of Spanish researchers (164 kg m-1 per application). The coefficient of translocation for disk and chisel plough were 114 and 93 kg m-1 per application, respectively. According to researchers from Portugal, the coefficients of translocation for disk and chisel plough were in ranges of 0-333 kg m-1 and 18-770 kg m-1 per application, respectively. The magnitude of soil translocation coefficients for tillage instruments were in order of MB plough > disk plough > chisel plough. Keywords: Aggregate mean weight diameter, Bulk density, Soil coefficient of translocation
Land Evaluation and Suitability
Javad Givi; Hojat Dialami; Mehdi Naderi Khorasgani
Abstract
Background and objective: In the assessment of land suitability, the land-production capacity is identified and the type of use is determined in proportion to that capacity. In this regard, the FAO approach has been used by many scholars in different parts of the world and Iran in land suitability assessment ...
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Background and objective: In the assessment of land suitability, the land-production capacity is identified and the type of use is determined in proportion to that capacity. In this regard, the FAO approach has been used by many scholars in different parts of the world and Iran in land suitability assessment studies. In this approach, the most commonly used method is the parametric method. The FAO approach uses Boolean logic to assess land suitability. This logic has been criticized by a number of land evaluation researchers. Because it does not take into account the continuous nature of the soil variations along the earth's surface and the uncertainty in the measurements. To overcome these shortcomings, the fuzzy analytical hierarchy process (FAHP) was presented to determine the land suitability classes. Land suitability should be determined based on a fuzzy analytical hierarchy process, in which, unlike the FAO method, unequal importance for different land characteristics and continuity of soil variations are considered. This research was carried out with the aim of qualitative land suitability evaluation in Dashtestan area, Bushehr province for Kabkab date palm (Phoenix dactylifera L. cv Kabkab) plantation, using two methods of FAO parametric (second root formula) and fuzzy analytical hierarchy process (FAHP) and comparing these two methods. Materials and methods: The study area is located in Dashtestan region, Bushehr province, Iran; between latitudes 29º 12΄ and 29º 31΄ N and longitudes 51º 09΄ and 51º 59΄ E. Its surface area is 23000 ha. The mean annual rainfall in the area is 250 mm and its mean annual temperature is 27 °C. The soil temperature and moisture regimes are hyperthermic and ustic, respectively. The physiographic unit which is river alluvial plain is very gently sloping. 80 % of the Kabkab date palm plantation is present in the study area. In order to achieve the objectives of this research, 50 date palm groves, each with an area of at least 0.5 ha and a palm of Kababab cultivar, aged 20 to 25 years, with the same management level and having different soil, were selected as observation points. Then a soil profile was dug randomely in each date palm grove, with dimensions of 1.5 (length), 1 (width) and 1.5 (depth) meters and described, using soil profile description guide. Soils were sampled from different horizons of the profiles and the required physical and chemical analyses were carried out on the samples, according to the standard laboratory methods. The drilling site was chosen to have a date palm tree in each of the four corners of the profile. The yield of the four trees located in four corners of each profile was measured and their average yield was considered as the final yield for the corresponding profile. Meteorological data was collected for a 10 year period from the nearest synoptic station (Borazjan station, Borazjan, Bushehr). Land indices were calculated, using soil and climatic data and parametric (second root formula) and fuzzy AHP methods. Weighted average of the climatic and the soil data was used and finally a land index was calculated for each soil profile. In the fuzzy AHP method, relative weight of each of the studied criteria was determined by analytical hierarchy analysis with establishment of pair wise matrix. Degree of membership for each soil and climatic criteria was also determined through membership functions and finally, land suitability classes were determined. At the end, accuracy of the methods was also compared. Landscape characteristics such as slope, drainage and soil depth were not considered in the land evaluation, because these characteristics did not show any limitation for the date production in the study area. Results: The results of qualitative land suitability evaluation based on fuzzy AHP method showed that 96.6 and 3.4 percent of the studied area are classified as S2 and S3, respectively. This is in the case that based on parametric (second root formula) method, 82 and 18 percent of the studied area are marginally suitable and non-suitable, respectively. According to these results, higher land suitability classes were obtained, based on fuzzy AHP than through parametric method. Correlation between the calculated land index and the measured yield, determined for the fuzzy AHP method was higher than the one obtained for the parametric method. This proves that the fuzzy AHP is a more appropriate method for land suitability assessment for Kabkab date palm plantation in the studied area than the parametric method (second root formula). Conclusion: According to the results of this research, the fuzzy AHP is a more appropriate method for qualitative land suitability evaluation than the parametric method (second root formula) for Kabkab date palm plantation in the studied area in Bushehr province.
