Soil compaction on traffic lane due to soil tillage and sugarcane mechanical harvesting operations

ABSTRACT: Mechanical sugarcane harvesting increases soil compaction due to the intense traffic of agricultural machinery, reducing longevity of sugarcane crops. In order to mitigate the harmful effects caused by agricultural traffic on the soil structure in sugarcane fields, this study evaluated impacts of mechanical sugarcane harvesting on traffic lane under two soil tillage systems based on load bearing capacity models. The experiment was carried out in the region of Piracicaba, state of São Paulo, Brazil, on a Rhodic Nitisol, under conventional tillage (CT) and deep strip-tillage (DST). For CT soil tillage was applied to the entire area with a heavy disk harrow, at operating depths from 0.20 to 0.30 m followed by a leveling harrow at a depth of 0.15 m. For DST, soil tillage was performed in part of the area at a depth of 0.80 m, forming strip beds for sugarcane planting, while the traffic lanes were not disturbed. Undisturbed soil samples from traffic lanes were used in the uniaxial compression test to quantify preconsolidation pressure and to model the soil load bearing capacity. The surface layer (0.00-0.10 m) was most susceptible to compaction, regardless of the tillage system (CT or DST) used. In the DST, the traffic lane maintained the previous soil stress history and presented higher load bearing capacity (LBC) than the traffic lane in the CT. As in CT the soil was tilled, the stress history was discontinued. This larger LBC in DTS minimized the impacts of the sugarcane harvest. Under CT, additional soil compaction due to mechanical sugarcane harvesting in the traffic lane was observed after the second sugarcane harvest. There was a reduction in load bearing capacity from 165 kPa to 68 kPa under CT and from 230 kPa to 108 kPa under DST, from the first to the second harvest at surface layer. Water content at mechanical harvesting was the most relevant factor to maximize impacts on the soil structure in traffic lanes, for both tillage systems.

摘要：机械化甘蔗收割作业因农用机械的高频通行引发土壤压实问题，进而缩短甘蔗种植周期。为缓解农用机械通行对甘蔗田土壤结构造成的不良影响，本研究基于土壤承载力模型，评估了两种耕作制度下机械化甘蔗收割对通行带的影响。本试验于巴西圣保罗州皮拉西卡巴地区开展，供试土壤为红化低活性淋溶土（Rhodic Nitisol），设置常规耕作（conventional tillage, CT）与深条带耕作（deep strip-tillage, DST）两种耕作模式。常规耕作模式下，采用重型圆盘耙对全区域进行耕作，作业深度为0.20~0.30 m，随后使用平土耙开展0.15 m深度的平整作业。深条带耕作模式下，仅对区域局部进行0.80 m深度的土壤耕作，形成用于甘蔗种植的条带床，而通行带则不受扰动。采集通行带的原状土样开展单轴压缩试验，以量化前期固结压力并构建土壤承载力模型。无论采用何种耕作模式，表层土壤（0.00~0.10 m）最易发生压实。深条带耕作模式下的通行带保留了初始土壤应力历史，其承载力（load bearing capacity, LBC）高于常规耕作模式下的通行带。由于常规耕作模式下土壤被全面翻耕，其初始应力历史被中断。深条带耕作模式下更高的承载力降低了甘蔗收割作业对土壤的影响。常规耕作模式下，在第二次甘蔗收割后，通行带出现了由机械化甘蔗收割引发的额外土壤压实现象。表层土壤的承载力在两次收割间出现下降：常规耕作模式下从165 kPa降至68 kPa，深条带耕作模式下从230 kPa降至108 kPa。对于两种耕作模式而言，机械化收割时的土壤含水率是影响通行带土壤结构受损程度的最关键因素。