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
针对咖啡种植园实施的新型管理措施，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系统对土壤承载力及农业机械通行临界土壤含水量的影响。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学院里奥蓬巴分校（Federal Institute of the Southeast of Minas Gerais - Rio Pomba College）试验田开展。试验地块的土壤以黏粒质地为主，为贫养红黄色氧化土（Dystrophic Red-Yellow Oxisol，葡萄牙语对应分类为Latossolo Vermelho-Amarelo distrófico，编号LVA7）。研究人员分别在传统全光照单作小粒咖啡（Coffea arabica L.）园，以及与银合欢（Gliricidia sepium）间作的遮阴咖啡园的咖啡株行间中央位置，随机采集0.00~0.03 m、0.12~0.15 m及0.27~0.30 m土层的原状土样，通过单轴压缩试验并拟合土壤承载力模型，以测定预固结压力。本研究估算了3台用于机械化农事作业的农用拖拉机对土壤施加的平均、最大法向应力及垂直应力分布特征，并确定了两种管理模式下拖拉机通行的临界土壤含水量，可为该区域评估额外土壤压实风险提供决策支撑。研究结果显示，咖啡与银合欢间作并不会对土壤承载力产生显著影响。在两种管理模式下，0.12~0.15 m土层均为最易受垂直应力影响的脆弱层位。阿拉格尔4100（Agrale 4100）、麦赛福格森265（MF 265）及麦赛福格森275（MF 275）三种拖拉机的垂直应力分别为335.76 kPa、200.24 kPa及245.55 kPa；且在所有研究土层中，全光照单作咖啡园的土壤无塑性变形通行含水量均高于遮阴间作咖啡园。