Kazuhiko Ohmiya

Characteristics of Salt-affected Soils by Deep Tillage up to 600 mm -Disaggregation Experiments of Soil Clods-

Abstract A method is proposed for soil improvement of salt-affected soils. We envisaged that a layer of about 600 mm in depth could be tilled by a special plough, producing a coarse layer (soil clods) in the subsoil (B and C horizons) and cutting off the capillarity rise of groundwater. In this paper, indoor testing with soil bins was used to determine the proper size of the soil clods produced in the subsoil which will be used for design of a new plough configuration. The results showed that the porosity of the subsoil reached 0.49 where capillarity restarted, after 2000 mm of precipitation. The size of the soil clods of the B horizon should be about 10 cm to prevent collapse and loss of volume of the topsoil (A horizon). That of the C horizon should be about 14 cm to keep a longer capillarity interception.

Fractal dimensions of terrain profiles

Abstract Analysing terrain profiles of fields, roads, and other terrains, it was determined that terrain profiles are random and non-periodical. Mandelbrot has defined non-scaling, self-similar figures as fractals, and many investigators have tried to characterize natural forms and structures using fractal geometry. The work here investigates whether terrain profiles can be defined as fractals. Fractal dimensions of profiles were calculated. These were compared with a locus of Brownian motion further to investigate characteristics of terrain profiles. Fractals are defined to be self-similar and irregular. Measuring and analysing terrain profiles, it was established that the statistical characteristics of any part of a terrain profile are similar and that the statistical characteristics of profiles of any kind of terrain are similar irrespective of roughness. This means that terrain profiles are self-similar, and irregular. From these results, it was determined that terrain profiles are fractals. The fractal dimensions were calculated with a coarse-graining method and by Power Spectral Densities (PSD), and fractal dimensions by Scaling were between 1.1 and 1.8 and by PSD between 1.3 and 1.5. Using the locus of Brownian motion, fractal dimensions were 1.5 or slightly larger than those of the terrain profiles. Fractal dimensions for the locus of smoothed Brownian motion were nearly equal to terrain profiles. Therefore terrain profiles could be artificially generated from the locus of smoothed Brownian motion. It appears that terrain roughness is formed by random and non-periodical force.

Characteristics of Farm Field Profiles as Sources of Tractor Vibration

Abstract To evaluate farm field profiles as sources of tractor vibration, profiles of meadows, roads and rough terrains were measured and analyzed. A slope angle measuring apparatus with a vertical gyroscope was made to measure profiles using the slope integration method. Periodic uneveness was not found in the measured profiles: therefore it may be assumed that profiles of farm fields, except plowed fields and fields with furrows, are random and non-periodic. Power spectral densities (0.05–3.0 cycles/m) of measured profiles could be approximated by a straight line on a log-log paper. The mean value of spectral slope (2,3) was steeper than that of the recommended value by ISO/TC108/SC2. However, it is suggested that the classification by ISO may be useful to select the profiles of test tracks for the vibration test of tractors and the durability test of tractors and implements. Then the coherency functions were calculated to investigate the correlation between two parallel tracks spaced for the tread width of tractor (1.5m), and the value of coherency functions were small beyond 0.2 cycles/m of spatial frequency. Therefore it is surmised that profiles of paths of tractor wheels are independent.

Deep Tillage Plough down to 600 mm for Improvement of Salt-affected Soils: Part 1: Configuration of Plough for Production of Large Soil Clods in Subsoil*

Abstract A method is proposed for soil improvement of salt-affected soils. Soil clods of desired size are produced in subsoil by deep tillage to cut off capillarity from groundwater and to prevent the rise of salts to the soil surface. In this paper, the plough configuration to produce soil clods with the proper size by brittle fracture was analysed in an indoor soil bin. The results showed that when brittle fracture (tensile failure) took place in the soil, a horizontal crack in the soil was produced at the tip of the plough blade, followed by an another upward crack toward the soil surface with the angle of about 40°. A short blade length (50 and 80 mm) and deep ploughing (150 and 200 mm) of the deep tillage plough generated unwanted huge soil clods of about 25 kg. In order to generate proper soil clods, the ideal rake angle should be 20°, and the ideal blade length was 130 mm.

Deep Tillage Plough down to 600 mm for Improvement of Salt-affected Soils:—Part 2: Draught and Vertical Force Induced on Plough by Brittle Fracture—

Abstract A method is proposed for soil improvement of salt-affected soils. Large soil clods are produced in subsoil by deep tillage to cut off capillarity from groundwater and to prevent the rise of salts to the soil surface. In this paper, the draught and vertical force induced on this plough body by brittle fracture (not by shear failure) was analysed to get the large soil clods in an indoor soil bin with a soil with cement. The results showed that the normal mean peak draught was about 1 kN, and the downward vertical peak force was about 10 kN at 200 mm in the operating depth. When the blade length was short (50 mm or 80 mm) and huge soil clods were produced, the peak draught and vertical force increased to about 2 kN and 20 kN respectively. When the blade length was long (200 and 250 mm) and the operating depth was deep (150 and 200 mm), the peak draught increased abnormally to 4–5 kN. The peak vertical force also increased abnormally to 30–40 kN. The proper length of the plough blade was determined to be 130 mm because of the smallest draught and downward vertical force.

Improvement of Salt-affected Soils by Deep Ploughing: —Part 2: Plot Field Tests in a Sodic Soil (Solonetz) Region—*

Abstract A method was investigated for improvement of salt-affected soils in regions where a sufficient amount of rainfall to percolate into subsoil occurs in summer. A coarse layer is provided in the subsoil by deep tillage, making soil clods to cut off the capillary rise from groundwater. This paper deals with plot test fields constructed by hand in a local spot of a sodic soil (solonetz) region. The results showed that deep tillage up to the subsoil (C horizon) was beneficial for improvement of the solonetz soil. Application of the gypsum also reclaimed the solonetz soil, and should be mixed into the A horizon. The pH values decreased from about 10 to 9. The EC values decreased from about 8 dSm -1 to 2 dSm -1 .

Sintering of Salt-affected Soils — Part 2: On-board Sintering of Soil —

A new method is proposed for soil improvement of salt-affected soils in regions where a sufficient amount of rainfall occurs in summer. The subsoil is made coarse by soil sintering, and the capillarity from groundwater is cut off. Thus, the rise to the soil surface of salts which are dissolved in the groundwater is prevented. Moreover, the salts that accumulate in the topsoil are washed out by rainfall (leaching) during the summer season. In this paper, based on the previous experiments of soil sintering, a prototypical soil-sintering plough was developed to make soil coarse. A stationary soil-sintering device was used to determine optimal conditions of thickness of spread soil on the conveyor, and conveyor speed. When this soil thickness was 15 mm and the conveyor speed was 5.7 mm s-1, the maximum thermal efficiency (about 30%) was obtained. When these conditions were applied to a prototypical soil-sintering plough attached behind a tractor, the required plough travel speed was 1.9 mm s−1 (6.84s10−3 km h−1) for practical use with 3 burners, 90 mm in the operating depth and 300 mm in the operating width.

Improvement of Salt-affected Soils by Deep Tillage: Part 2: Large-scale Field Tests in a Sodic Soil (Solonetz) Region*

A deep tillage method was tested for soil improvement of salt-affected soils. Capillary rise of groundwater was cut off by the deep tillage, which made a coarse layer in the subsoil. This paper deals with large-scale field tests constructed by a four-stage subsoil plough in a sodic soil (solonetz) region. The results showed that the deep tillage down to the subsoil proved positive for the improvement of the solonetz soil. In the deeply tilled field, the grass height and density of cultivated natural pasture were much greater than those in the conventional (subsoiled) field. In the subsoiled field, the grasses were growing at the areas on the subsoiler channels, but their grass height was much shorter than in the deeply tilled field. At the undisturbed areas between the subsoiler channels, the grasses could not survive at all.

Deep Tillage Plough down to 600 mm for Improvement of Salt-affected Soils: Part 3: Field Experiments*

Abstract A method is proposed for soil improvement of salt-affected soils to till down to about 600 mm in depth by a special plough. The goal is to cut off the capillary rise of the groundwater by creating a coarse layer of tilled subsoil. Earlier, a plough configuration to produce soil clods with the proper size in the subsoil was determined in an indoor soil bin. In this paper, we designed and tested prototypical plough bodies in field experiments. A plough blade length less than 130 mm produced large soil clods and a blade length more than 130 mm generated small ones. With any length, deeper operating depth caused larger soil clods to form. The proper specifications of the third and fourth plough bodies of the special plough are as follows: the plough blade length is 130 mm, the operating width is 300 mm, the operating depth is 200 mm and the cutting angle is 20°.

Field Operation of an Artificial Perched Watertable Machine

To retain summer runoff rain-water, an artificial perched watertable was constructed at about 0.5 m depth in an area where the annual precipitation occurs mostly in the summer season. The water in the sand-filled permeable layer could be used as capillary water for plants in the dry spring season. A special machine was developed to create the artificial perched watertable. This paper deals with the field operation testing of this machine. The results showed that when the soil water content was more than the plastic limit (PL) and the soil penetration resistance of the field was less than 2 MPa, the penetrating velocity of the injector into ground was constant at about 50 mm s−1 and a insert of 0.5 m in depth was obtained. A perfect underground cavity was produced due to the horizontal rupture fracture of the soil, when the soil water content was more than 25% d.b. Hence, when this machine is operated in a field, in order to obtain the perfect insert of the injector and the perfect underground cavity production, the soil water content should be more than the plastic limit. Charging air into the charge tank and charging sand into the sand tank occupied 98% of the total time. Charging air into the charge tank required 93% of the total operating energy.