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
Anahid Salmanpour; Mohammad Hassan Salehi; Jahangard Mohammadi; Abdolmohammad Mehnatkesh; Sayyed-Hassan Tabatabaei
Abstract
Introduction One of the objectives of land evaluation method is determining the land suitability degree and class in case of making any changes, including causing elimination or limitation. Thus, as an example, if it could be possible to predict changes in soil salinity for the future, any changes in ...
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Introduction One of the objectives of land evaluation method is determining the land suitability degree and class in case of making any changes, including causing elimination or limitation. Thus, as an example, if it could be possible to predict changes in soil salinity for the future, any changes in land suitability class can be investigated based on the predicted variations over time.The most important crops in Neyriz area are wheat and barley. Unfortunately, over the past two decades, improper agricultural management caused reduction and salinization of irrigation water in this region. To this end, the present study was performed to investigate the possibility of changes in the class or degree of land suitability in case of variations in soil electrical conductivity due to irrigation with saline water in Neyriz, for the next 10 years. Materials and Methods In three soil map units in three regions consisting of Deh-Fazel, Tal-Mahtabi and Nasir Abad, wheat and barley fields were selected and representative pedons were excavated, described and classified. Soil and water samples were obtained and necessary analyses and soil humidity and salinity, hydraulic conductivity and bulk density and water electrical conductivity were determined. Crop yields were evaluated by 1×1 quadrate, soil surface layer hydraulic conductivity was carried out by guelph permeameter and the volume of irrigation water was measured according to pipe discharge in each farm. Soil retention curve was calculated for all soil layers using sand box and pressure plate. van Genuchten equation parameters were gained using RETC software. Afterward, solute transport modeling was done using the software Hydrus and its results were validated using four statistical parameters including Coefficient of determination (R2), Root Mean Square Error (RMSE), Model efficiency (EF) and Coefficient of Residual Mass (CRM) to investigate the possible variation in soil salinity during the next 10 years, the data of the studied period of the crop year between 1392 and 1393 was repeated for 10 years. Qualitative and quantitative land evaluation was performed by standards methods. Finally, the Hydrus results were compared with salinity maps of Neyriz area which were calculated and obtained in the previous research from Landsat images bands for the past 20 years. Results and Discussion Based on the results, climate suitability class in Neyriz area was suitable (S1) for wheat and relatively suitable (S2) for barley. The limiting factor for barley was the average of maximum temperature in the coldest month for barley. The soil suitability class was suitable (S1) for both crops (wheat and barley) in all farms. Therefore, the land suitability in the studied farmlands was S1 for the wheat and S2 for the barley. Results also revealed that the values for potential production were 10723 and 8677.5 Kg(grain)ha-1 for wheat and barley and for critical production were 1167 and 1297.6 Kg(grain) ha-1 for wheat and barley, respectively in the farms. Amongst the farmlands, only a barley farm which was located in Tal-Mahtabi had the S1 quantitative suitability class and others had S2. The results also showed that if all other conditions like volume and the quality of the irrigation water, precipitation, temperature and evaporation remain constant over the next 10 years, land suitability class will not change but land suitability degree will decrease gradually over time. The validation of the Hydrus model, based on the RMSE values, revealed that the predicted soil salinity and the observed value were very similar and the model had good ability in estimating and modeling soil salinity in the studied area. Comparing the results of modeling and soil salinity maps over the last 20 years have confirmed this trend. Based on the satellite salinity maps, the soil salinity of the studied fields has increased slightly from 2 to 4 dSm-1 between the years 1374 and 1393. Hence it can be concluded that the prediction of Hydrus model about gradual rise in predicted soil salinity and land suitability degree during the next 10 years is acceptable. Conclusion The present study showed that climate and land suitability class in Neyriz area was suitable and relatively suitable for wheat and barley, respectively. Solute transport modeling showed that land suitability degree will decrease gradually and soil quality will decline over time by assuming constant irrigation and precipitation condition over the next 10 years. Therefore, preventing the expansion of soil salinity and degrading agricultural lands require serious considerations of the authorities in the crisis Managements.
H. Khdemi; J. Mohammadi; M. Nael
Volume 29, Issue 3 , December 2006
