Load-bearing capacity and critical water content of the coffee plantation soil with management in full sun and shaded

ABSTRACT New management practices applied to coffee crops may influence the soil’s capacity to tolerate vertical stresses. This paper aimed to evaluate the influence of two coffee crop management systems on the soil load-bearing capacity and critical soil water content to agricultural machinery traffic. This study was performed in the experimental area of the Federal Institute of the Southeast of Minas Gerais - Rio Pomba college, in Rio Pomba city, Minas Gerais, Brazil. Dystrophic Red-Yellow Oxisol (Latossolo Vermelho-Amarelo distrófico) (LVA7) with clayed texture predominating in the experimental unit. Undisturbed soil samples were collected from layers of 0.00-0.03, 0.12-0.15 and 0.27-0.30 m, randomly, in the center of the interrows of coffee plants (Coffea arabica L.) in monoculture plots under traditional management (in full sun) and in the plots of coffee plants intercropped with gliricidia (Gliricidia sepium) (shaded) to estimate pre-consolidation pressures, through uniaxial compression tests and adjustment of soil load-bearing capacity models. The average and maximum normal stresses applied to the soil and the vertical stress distribution of three agricultural tractors used in mechanized farming operations were estimated, and the critical soil water content to the traffic of these tractors was determined for both treatments, aiding in the decision-making process regarding additional compaction risks in the area. Cultivation of gliricidia in consortium with coffee did not influence the soil load-bearing capacity. The soil layer of 0.12-0.15 m was the most vulnerable to vertical stresses in both treatments. Agricultural tractors Agrale 4100, MF 265 and MF 275 presented values of vertical stresses of 335.76, 200.24 and 245.55 kPa, respectively, and the soil water content for the traffic of agricultural machines without plastic deformation was higher in the coffee plants in full sun for all studied depths.

摘要：咖啡种植中采用的新型管理措施，可能会影响土壤耐受垂直应力的能力。本研究旨在评估两种咖啡种植管理模式对土壤承载能力（soil load-bearing capacity）以及农业机械作业临界土壤含水量的影响。本试验于巴西米纳斯吉拉斯州里奥蓬巴市的米纳斯吉拉斯州东南部联邦理工学院里奥蓬巴校区实验区开展。供试地块的土壤以黏粒质地为主，属于贫化红黄色氧化土（Dystrophic Red-Yellow Oxisol，巴西本土土壤分类为Latossolo Vermelho-Amarelo distrófico，编号LVA7）。研究分别在传统露地管理的小粒咖啡（Coffea arabica L.）单作地块，以及与银合欢（Gliricidia sepium）间作的遮阴咖啡地块中，随机于咖啡行间中部采集0.00~0.03 m、0.12~0.15 m及0.27~0.30 m土层的原状土样，通过单轴压缩试验（uniaxial compression tests）并拟合土壤承载能力模型，以测定前期固结压力（pre-consolidation pressures）。本研究估算了3台用于机械化耕作的农用拖拉机施加于土壤的平均、最大法向应力，以及其垂直应力分布特征；并确定了两种种植模式下拖拉机作业的临界土壤含水量，可为该区域评估额外土壤压实风险提供决策依据。咖啡与银合欢间作的种植模式并未对土壤承载能力产生显著影响。在两种种植模式下，0.12~0.15 m土层均为最易受垂直应力影响的敏感层位。Agrale 4100、MF 265及MF 275型农用拖拉机的垂直应力分别为335.76 kPa、200.24 kPa及245.55 kPa；且在所有供试土层中，露地单作咖啡地块的农业机械无塑性变形作业土壤含水量均高于遮阴间作地块。