Abstract:
Abstract: Soil compaction become very serious problem due to many years of traditional tillage practices which result in formation of hard plow pan, shallower rooting depth, decreased air and water permeability, and confined root system development. Subsoiling and straw incorporated into soil applied jointly result in good working efficiency, alleviation of plow pan by subsoiling, improved water holding capacity and buried crop residue. This is direct and effective way of improving organic matter contents and it can also effectively alleviate the environmental pollution caused by straw burning. This practice will not only reduce wheel traffic in field, it also will save busy time in farming season and will play an important role in increasing crops yield and farmer’s income. Through the study of relevant literature, in order to meet the needs of deep tillage and straw burying at the same time, a multifunctional machine for subsoiling and rotary burying have designed, which was capable of joint operations like subsoiling, stubbles cutting, soil crushing, residue burying and leveling. Subsoiling implement with self-excited vibration and adjustable pre-tightening force were devised in this machine which worked to reduce subsoiling resistance to certain degree and also protected the subsoiler when it encountered obstacles. The principle of sliding cutting was adopted in the design of the deep shovel bar which can cut off straw and weeds effectively and prevented winding and clogging to the subsoiler bar. The stress analysis of the subsoiling implement was carried out and the force formula was determined. Blades of rotary cutter were rearranged and optimized to improve working stability and soil cutting and crushing capacity. Subsoiling provided good condition for rotary burying and the depth of straw embedment was increased. Different field tests such as separate subsoiling, rotary burying after subsoiling, separate rotary burying and subsoiling with rotary burying as combined operation was carried out. The traction resistance and power consumption of implement under different working conditions were analyzed. Results showed that the traction resistance and power consumption of subsoiling operation was greatly affected by the working speed. In the rotary burying operation, the driving force of the positive rotation of the rotary cutter roll was opposite to the working resistance so that the cancel out and the traction power consumption of rotary burying operation were small, and power ratio for rotary burying was more. Under the 1st and 2nd gear speeds of the tractor, the total power respectively for the combined operation of subsoiling and rotary burying was 32.72 and 41.88 kW. They accounted for 85% and 82.2% of the total sum of individual subsoiling and rotary burying operations, respectively. Through consulting relevant documents, compared with the traditional machine for subsoiling and rotary tillage, the power consumption was reduced by 4.4% to 14.8% and 7.9% to 14.0%, respectively in the same working condition. Other parameters of experiment collected after combined operation of subsoiling and rotary burying and statistically analyzed included average depth of subsoiling. The results showed that rotary burying were 28.9 and 17.5 cm, respectively, subsoiling tillage stability was 93.5% and rotary burying tillage stability was 87.4%, the average vegetation cover rate was 92.0%, the surface evenness after tillage was 1.0 cm, and soil resistance of 0-15 and 15-30 cm after tillage were 437.6 and 951.8 kPa, which were 78.4% and 67.4% less than that before tillage, respectively. Soil bulk density of 0-10 and 10-20 cm after tillage were 1.40 and 1.41 g/cm3 which decreased by 6.7% and 8.4%, respectively compared with that before tillage. The performance evaluation indexes of subsoiling field preparation combine machine were compared, and the measured values of the above parameters for combined operation of subsoiling and rotary burying exceeded the quality evaluation index and meet the agronomic requirements.