Relationship model of fertilizer outlet location and fertilizer application depth of depth-fixed application device of base-fertilizer

Winter wheat is the most important crop in China, which has a large planting area, a high per unit area yield and a high total output. This is important to the maintenance of national food security. Base-fertilizer application is an important process of winter wheat production, which directly affects the yield of crops, and reasonable and effective use of chemical fertilizer can improve the yield of crops. At present, base-fertilizer of winter wheat is applied to the surface of farmland by manure spreader or laborers. Then the rotary tiller or moldboard plow is used to bury the fertilizer underground. The method has the problems of disordered fertilizer, excessive fertilizer delivery and low utilization efficiency. The depth-setting fertilizer application for winter wheat is an ideal way of fertilization. It can carry out a uniform fertilization to the winter wheat’s underside position with a certain depth, which can reduce fertilizer amount compared with the traditional fertilization operation. It is a fertilization technique with high output, stable yield and low cost. Combined with the characteristics of rotary tillage fertilizing of winter wheat in Huanghe-Huaihe-Haihe (HHH) zone of China, this paper proposes a precise depth-setting fertilizer application method based on principle of rotary tillage. From the kinematics analysis of rotary blade and soil block respectively, the mathematical model of the positions of fertilizer outlet orifice of steel pipe and the target depth of fertilization was established. In order to validate this mathematical model, a precision rotary tillage fertilization test platform was set up. The test platform includes tractor, depth-controlled component, rotary tillage device, fertilizer ejecting device, precision hydraulic control system and press device. The fertilizer ejecting device is the key part of the test platform. It includes longitudinal beam, fastening bolt, steel pipe of fertilizer ejecting, U-shaped bolt and sleeve. The steel pipe of fertilizer ejecting can be adjusted longitudinally and laterally according to the requirements of the test. In order to accurately validate the mathematical model, 2 groups of progressive experiments were designed and conducted at the National Experiment Station for Precision Agriculture in Xiaotangshan Town, Beijing City in October 2017. After testing, the hardness, humidity and temperature of soil in the test area at the depth of 0-10 cm were 615.0 kPa, 10.9% and 17.6 ℃, respectively. In the experiment, the IT245 rotary blade cutting operation parts were selected, and power transfer mechanism used John Deal 1204 tractor. The tractor was controlled at the speed of 1.5 m/s, the rotational speed of rotary blade was stable at 180 r/min, and the rotary tillage depth was set to 200 mm in the verification test. The experiment selected blue fertilizer as the application object. Target fertilization depth was set as 80, 100, 120, 140, and 160 mm, respectively, for the precision fertilization field test, and the actual depth of fertilization was 73, 92, 111, 132 and 151 mm, respectively. The maximum offset deviation of fertilization depth was 9 mm, and the maximum deviation ratio of fertilization depth was 8.75%, which could meet the requirement of the actual production. The results of these experiments show that the mathematical model of the positions of fertilizer outlet orifice of steel pipe and the target depth of fertilization established is trustworthy. The results can be a theoretical basis for design and development of rotary tillage and fertilization equipment.