Strip tillage characteristics of rotary tiller blades for use in a dryland direct rice seeder

Abstract

A minimum tillage technique is required for reducing the labor requirements to prepare a level rice seedbed in Korea. Thus this study was aimed at determining the strip tillage characteristics of rotary tiller blades for use in a dryland direct rice seeder. The experiments were carried out in a laboratory soil bin. The USDA textural classification of the experimental soil was sandy loam. Soil hardness measured by cone penetrometer ranged from 245 to 1442 kPa depending on the depth, and the soil moisture content was 34.6%. The effects of rotary blade shape, rotational direction, number of rotary blades around the periphery, with and without soil-cutting disc blades on soil break up and torque requirements were investigated. Three different types of rotary blade were used, two general purpose rotary blades used with tractors and power tillers, and a leveling rotary blade for tractor use in wetland paddy fields. Rotation in the opposite direction to travel and cutting upwards resulted in soil being scattered out of the seeding furrow. A down-cut process is therefore necessary for effective seedbed preparation of a rice field by strip tillage using a rotary tiller. Of the three types of rotary blade, the rotary blade for the power tiller was considered most satisfactory for strip tillage on a basis of its torque requirement and the ratio of soil breaking. The rotor shaft with four rotary blades had the lowest torque variation and torque requirement and ratio of soil breaking was 24.4%. The width of seedbed prepared by the rotary tiller with four blades during the down-cut process was 80 mm which was enough for direct seeding of rice and applying fertilizer. Though a soil-cutting disc blade helped produce a better seedbed furrow, the increased friction between the disc blade and the soil block generated a much higher torque requirement. The soil-cutting disc blade was not necessary for the strip tillage direct rice seeder. Based on the results a strip tillage technique by the power tiller blade with a down-cut process could be effectively used for a dryland direct rice seeder.