不同生育期烤烟根系固土能力特征研究

Soil fixing ability of flue-cured tobacco roots at different growth stages

本研究选取云南省主要种植作物--烤烟为试验材料,分析烤烟不同生育期（团棵期、现蕾期、成熟期）的根系固土能力特征。应用锚杆拉力计和自行设计的剪切箱对不同生育期烤烟根系的固土能力在0-10 cm和0-20 cm土层进行原位测定。结果表明：同一生育期,根系密度表现为0-10 cm〉0-20 cm；同一土壤深度范围内,根系密度表现为成熟期〉现蕾期〉团棵期。相同深度范围内,固土能力表现为成熟期〉现蕾期〉团棵期；在现蕾期和成熟期,固土能力表现为0-10 cm〉0-20 cm,而团棵期由于根系尚未深扎至20 cm深度,只有在样方的塑性变形阶段的固土能力,表现为0-10 cm〉0-20 cm；同一生育期相同深度范围内,载荷与位移间呈现显著的直线相关关系（P〈0.01）。随着载荷的增加,将出现载荷临界点F1、F2和F3, F1为比例极限点, F2为屈服拉力点, F3为抗拉极限点。相同深度, F1与根系密度间无明显相关关系, F2和F3分别与根系密度间呈显著幂函数关系。在0-10 cm, F2与根系密度和F3与根系密度的相关方程分别为y=1.313x0.042和y=1.379x0.084；在0-20 cm, F2与根系密度和 F3与根系密度的相关方程分别为 y=1.389x0.048和 y=1.638x0.077。该测定方法可以在水土保持上作为评价不同作物（植物）固土能力的有效参考手段,建立不同作物根系固土数据库,为坡耕地作物配置提供理论依据。

Flue-cured tobacco （Nicotiana tabacum） is the main crop in Yunnan Province. The characteristics of soil fixing ability of flue-cured tobacco roots at different growth stages （rosette stage, budding stage and maturity stage） were measured in situ with the anchor-shank tensiometer and self-designed shearing box at soil depths of 0-10 cm and 0-20 cm. The results showed that the order of the root density of flue-cured tobacco for different depths during the same stage were 0-10 cm〉0-20 cm. The order of the root densities of different growth stages for the same depth were maturity stage〉budding stage〉rosette stage. The soil fixing abilities of flue-cured tobacco roots for the same soil depth were in sequence of maturity stage〉budding stage〉rosette stage. Then the soil fixing abilities of roots for different soil depths during the budding stage and maturity stage were 0-10 cm〉0-20 cm. The soil fixing abilities of roots during rosette stage of sampled squares was 0-10 cm〉0-20 cm as roots hardly reached 0-20 cm of soil depth. For the same growth stage and soil depth, the load and displacement of sampled soil squares were in significant liner correlation （P〈0.01）. With increasing load, three critical load points appeared：tensile proportional limit （F1）, tensile yield strength （F2） and tensile strength limit （F3）. For the same soil depth, no significant correlation was noted between F1 and the density of flue-cured tobacco roots. However, the correlations between F2 and root density and between F3 and root density were that of power regression. For the of 0-10 cm soil depth, the correlations between F2 and root density and between F3 and root density were as follows：y=1.313x0.042 and y=1.379x0.084, respectively. For the 0-20 cm soil depth, the correlation equations for F2 and root density and for F3 and root density were y=1.389x0.048 and y=1.638x0.077, respectively. It was proposed that anchor-shank tensiometer and self-designed shearing box were effective in analyzing the characteristics of soil fixing ability of flue-cured tobacco roots at different growth stages.