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.
To achieve the maximum benefit of no-tillage with cover crop in the sustainable farming system, we conducted experiments on the performance and power consumption of a no-tillage seeder under different combinations of cover crop species, residue management and termination in soybean production. The results showed that the power consumption of the no-tillage seeder was higher with rye than hairy vetch and mixed-seeding, and increased with higher quantity of cover crop residue. The termination and management of cover crop significantly affected the cover crop biomass accumulation and power consumption of the no-tillage seeder. The results revealed that late cover crop termination increases the biomass while the performance of the no-tillage seeder declined. Therefore, flail mower cutting and mix seeding were appropriate for improving the no-tillage seeder in soybean production.
We investigated difference in effects between periodic and one-time application of digested slurry (PDS and 1DS, respectively) to wet rice fields by a slurry irrigation system using controlled pot cultivation and actual wet rice field tests. Fertilizer application rates were 120 kgN/ha for PDS and 220 kgN/ha for 1DS. Both experiments gave similar results for growth duration and nitrogen (N) use efficiency. During the tillering stage, plants after PDS had lower stem number and SPAD values (chlorophyll content of leaves) than plants after 1DS, but the values increased during the panicle initial stage and were higher than 1DS during the ripening stage. PDS exhibited significantly higher levels of N uptake, agronomic efficiency, and fertilizer N recovery efficiency than 1DS.
We propose direct seeding into the previous year's stubbles as a labor-saving rice cultivation method in untilled dry paddy fields. The effectiveness of this method was determined by conducting a seeding experiment. Three seeding holes at depths of 20 or 40 mm were bored per stubble, and 4 or 7 seeds were sown per stubble. Four sets of experiments were designed with different combinations of seeding depth and seeding number, and each set of conditions was replicated 3 times. Germination rate and stubble width were determined 1 month after seeding. Our results suggest that seeding in stubbles may be effective in preventing bird damage typically noted in shallow seeding but that deep seeding restricts seedling growth through shielding of sunlight.
We hypothesized that direct seeding into the previous year's stubbles in untilled dry rice fields would be a labor-saving rice cultivation method and sought to determine the effectiveness of this method. Three seeding holes (depth, 20 or 40 mm) were bored per stubble, and 4 or 7 seeds were sown in these holes. Four sets of experiments (performed in triplicate) were designed with different combinations of seeding depths and seed numbers. Each experimental plot (2 × 2 m) included 91 stubbles at 150-mm intervals with 300-mm inter-row distances. As a control, 7 seeds were sown in a ditch (depth, 20 mm). Productive panicle number and winnowed paddy yield were determined after harvesting. The experimental results demonstrate the effectiveness of our seeding technique.
Relationships between higher heating values (HHVs) and major constituents (carbon, nitrogen, moisture, ash concentrations) of rice straw while examining storage conditions were investigated. Different storage periods and temperatures affect major constituents. To obtain high-accuracy predictions for HHVs, we analyzed the relationship between carbon and nitrogen concentrations, which is a better method than analyzing moisture and ash concentrations. HHV is calculated as 17007.89 - 9.17t+0.05T, where t and T are the number of storage days and biomass temperature, respectively, with coefficient of determination = 0.801 and significance level = 0.05. HHVs obtained from this relationship agreed well with those obtained using a bomb calorimeter, indicating that this relationship has the potential for use in estimating HHVs of rice straw.
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