Design and experiment of pre-soil-breaking chisel-type subsoilers for banana field in hot areas of Hainan Province, China

Abstract: As one of the fruits widely planted in tropical areas, banana occupies an important position in the world fruit trade market. At present, in order to increase banana yield and improve banana quality, banana planting mostly adopts the "one in two years" mode. The operation times of agricultural machinery greatly increased because the short cycle banana planting mode combined with the traditional banana field tillage and rotary tillage mode, which results in the continuous compaction and formation of plough bottom under the soil tillage layer of banana field, then the soil surface roughness reduce. Rainwater is difficult to penetrate into the soil to form surface runoff and take away a large amount of surface soil and organic matter, affecting the growth of banana trees and banana production. Traditional subsoiling machines and tools generally have problems such as high work resistance, high energy consumption and low efficiency. At present, due to the regional characteristics of banana planting, the development and research of special subsoiler for banana field is still relatively weak, which seriously restricts the popularization and application of subsoiling technology in tropical agricultural areas. Firstly, the subsoiling method of the whole machine was determined in this study, and the three-dimensional model of the pre-soil-breaking chisel-type subsoiler was established. Based on the research of interval subsoiling method and inclined handle subsoiling mechanism, the structure of subsoiling shovel assembly, soil breaking disc and other key components were designed, and the force of subsoiling shovel tip and shaft was analyzed to ensure the working stability. At the same time, field experiments were carried out to determine the soil firmness and soil bulk density after subsoiling, and the factors that had significant effect on soil firmness and soil bulk density were determined, that was, working speed, subsoiling depth and penetration depth of soil breaking disc. Moreover, the second-order regression model of response value and significant parameters were obtained by taking soil firmness and soil bulk density as response values, and the optimal parameter combination was obtained by optimizing the significant parameters. The Box-Behnken test design was used to determine the optimal values of three significant factors: the working speed of the machine was 1.15 m/s, the subsoiling depth was 350 mm, and the penetration depth of the disc was 250 mm. The soil firmness was 734 Pa, the soil bulk density was 1.42 g/cm3 under the given optimized parameters. Furthermore, the verified test was carried out and the results showed that the error of soil firmness and the soil bulk density between the test value and the theoretical value were 2.4% and 4.2% respectively. Finally, the comparative results between the existing traditional subsoiling machines and pre-soil-breaking chisel-type subsoiler showed that the soil firmness of the developed pre breaking chisel subsoiler reduced by 6.39% and the soil bulk density decreased by 9.76%. which indicated that the pre-soil-breaking chisel-type subsoiler was more suitable for the subsoiling operation of banana field in Hainan hot area. The design of the machine can promote of subsoiling technology in tropical area of Hainan and supply references for application.