基于精确播深控制目标的播种单体田间台架试验

为了探明长江中下游稻麦轮作区单体精播技术的适配性及其农艺效应，揭示基于区域土壤力学特征的精密播种机设计原则，以2BMYFQ型免耕播种机单体为例开展田间台架播种试验，提出符合农机-农艺融合原则的4个精播主控目标和技术要素，探讨2种耕作处理方式（免耕、旋耕）、3个预定播深(2.5、4.0、6.0cm)和3个下压力（0.6、1.0、1.2kN）因子组合下的种子播深、土壤物理变化及小麦出苗效果。结果表明，播种单体与土壤力学性质交互影响并导致播深变化差异显著，土壤力学变异造成高达37.61%的播深变异，基于线性弹力张紧特征的下压力控制技术与不合理耕作方式组合下的精确播深控制目标无法实现。现有试验单体既存在土壤对双圆盘开沟器支撑力过大导致的限深轮虚支撑，也存在土壤支撑力不够且限深轮过度下陷导致农学意义上过深的种子位。单体造成种子位土壤压实状况也受耕作方式及下压力影响，并最终反映为出苗率的变化。综合比较发现，稻田原茬免耕、预定播深4cm、下压力1.2kN工况下，实际播深与预定播深差异较小，播深稳定性高，出苗率高，但种沟侧壁压实程度大；在旋耕条件时最优播深为预定播深4cm和下压力1.0kN组合；旋耕处理的单体播深控制整体效果优于免耕。因此智能精密播种技术应首先探明土壤力学条件和农艺播深目标的合理下压力控制策略，实现基于“播种单体-土壤力学关系”的单体创新设计和智能化土壤力学在线检测系统是区域精播技术的关键。

Field Bench Test of Seeding Unit Based on Precise Seeding Depth Control Objective

The mechanisms governing the precision of seeding depth and the related agronomic outcomes are site-specific. Regional soil mechanics in the Yangtze River Basin plays a role in affecting the relationship between the seeding unit and the soil, which is a key consideration for machine design. Using four technical objectives for evaluation, a field bench experiment was conducted in the field using a market available seeding unit (2BMYFQ) to illustrate the tool-soil interactions. Two tillage treatments (i.e. no-till and rotary till), three depth settings (i.e. 2.5cm, 4.0cm and 6.0cm) and three downward forces (i.e. 0.6kN, 1.0kN and 1.2kN) were adopted in the experiment. Seeding depth, soil properties after seeding and seedling establishment rate were measured. Results showed that the interactions between the seeding unit and soil mechanics affected seeding depth significantly. The maximum seeding depth variation was 37.61%. Results showed that linear elastic force depth control assembly plus the poorly managed seedbed made it impossible for precision seeding depth control. The mechanisms leading to the poorly controlled seeding depth were identified, including both the void soil support and the over sinkage of the ground wheel. Meanwhile, the seeding unit affected soil mechanics significantly, which in due resulted into non-uniform seedling establishment rate. Results indicated that the combination of the no-till, 4cm depth setting and 1.2kN downforce provided the best precision of the seeding depth. While in the tilled soil, 4cm depth setting and 1.0kN led to the best result. Overall, the depth control performance in the tilled seedbed condition was higher than that in no-tilled soil. The research result indicated that suitable downforce selection was inherently related to both soil mechanics and agronomically defined seeding depth. Inter-relationship between the seeding unit and soil mechanics as well as on-line soil monitoring system for downforce control were key measures for precision seeding in a given agricultural zone.