大区画水田の水稲作機械化作業体系と適正区画規模 第２報 大型機械利用のための適正区画規模

Abstract

A procedure to determine a “large-sized” paddy field size and turning method for the field machinery was developed and tested under field conditions. The optimal size of the “large-sized” paddy field is affected by the farm machinery work system, the farm management system, the geographical conditions, the climatic conditions, and the soil condition.We tested two types of turning for several shapes of paddy fields. One was the standard turning (turning in the field) and the other was the farm road turning (use farm road for turning.)Three sizes of fields were used to test the standard turning method. The resulting treatments in which the field length was a variable and the corresponding lengths were: T-1: 100m; T-2: 150m; T-3: 200m. The farm road turning method was tested on only one field length (T-4: 200m.)For land preparation and paddling work farm machines efficiency was increased with the width of the field for all field shapes. Efficiency was also increased with the increased field length, where treatment T-4 had the highest efficiency.The efficiency of high-speed rice transplanter showed similar trend to the Iand preparation and paddling machines. However, in general, the work efficiency was low because the effect of the field width expansion was not enough to compensate for the long replenishment time of the seedlings box.Farm machinery efficiency of herbicide scattering using riding type spraying and dusting machines also increased with the field length. The fact that the rate of herbicide application was low, enabled the machine to travel long distances before replenishment was needed.Moreover, the efficiency of the spraying machine was greatly influenced by the field width. When the quotient, of dividing the field width by two spraying widths (20*2=40m), was an integer the efficiency was high. However, when the quotient wasn't an integer (field widths 30, 60m etc.) the efficiency was low.The spraying width for top-dressing using riding type spraying and dusting machines had to be adjusted for long fields with only one side road. By using farm road turning, the farm machines efficiency was improved for top-dressing work. Again when the quotient, of dividing the field width by two spraying widths, was an integer the efficiency was high and low when the quotient wasn't an integer.Efficiency of multi-crop combine harvester, using the farm road turning where farm roads were on both sides of the field, was always high. Having roads on both sides of the field reduced the travel distance to empty the grain tank as compared with standard turning.Moreover, farm machines efficiency increased when the field area was smaller than two hectare. When the field area was larger than two hectare farm machines efficiency leveled off and in treatment T-3 there was a reduction in efficiency for larger field areas.The optimal field size for farm machines work was a function of turning type. The farm road turning required less time (sum of total machine utilization time*number of men) than the standard turning. Using the farm road turning, the effect of field width expansion was not consistent.When the field width was 100m or more, it was impossible to reduce total working hours. On the other hand, total working hours decreased in standard turning when field width was expanded by removing the borders. Total working hours decreased in a continuous rate for fields with small widths, and leveled off for fields larger than two hectare. The decrease in total working hours for two hectare field size was seventeen and twenty three percent as compared with the 0.3ha standard field size for treatments T-1 and T-4, respectively.Therefore, it was concluded that the optimal size of a paddy field is two hectare.