Temporal Variation of Soil Physical Quality under Conventional and No-Till Systems

ABSTRACT: Determination of soil physical quality (SPQ) is very important because it is related to many important soil processes. However, it is not clear which indicators should be considered in this evaluation, and information about temporal variation of SPQ under different soil tillage systems is scarce. The aim of this study was to determine the effects of no tillage (NT) and conventional tillage (CT) on temporal variation of capacity SPQ indicators [bulk density (BD), macroporosity (Pmac), air capacity (AC), plant available water capacity (PAWC), relative field capacity (RFC), Dexter's (S), and structural stability index (SSI)], and dynamic SPQ indicators [field saturated hydraulic conductivity (K0), water-conducting macroporosity (εma), and mesoporosity (εme); and pore continuity indexes based on water flux of total porosity (CWTP), of macroporosity (CWmac), and of mesoporosity (Cwmes)]. Additionally, the effect of the soil management system on corn yield was evaluated. Measurements and determinations were made at four different moments/cropping stages in the corn growing season (BS: before seeding; V6: six leaf stage; R5: physiological maturity; and AH: after harvest). Capacity SPQ indicators were derived from the soil water retention curve determined using sand box and pressure chambers, and dynamic SPQ indicators were derived from field infiltration data measured using a tension disc infiltrometer. Most capacity SPQ indicators were affected by the moment/cropping stage in which samples were taken, but followed similar trends and had similar values under both treatments, particularly in the AH stage. Dynamic SPQ indicators varied differently during the growing season depending on the management system. Under NT, most dynamic indicators increase from BS to V6 and decrease again at AH, whereas under CT, they follow a different trend, decreasing from BS to V6, remaining constant until R5, and increasing at AH. Corn yield was lower under CT (NT: 10,939 kg ha−1; CT: 8,265 kg ha−1). These results emphasize the need to include dynamic SPQ indicators, and their temporal variation when evaluating cropping systems with the aim of modeling crop yields. The capacity SPQ indicators were not able to distinguish between treatments.

摘要：土壤物理质量（soil physical quality，SPQ）的测定至关重要，因其与诸多关键土壤过程密切相关。但目前尚不明确该评价体系应纳入哪些指标，且有关不同土壤耕作体系下SPQ时间动态变化的相关资料十分匮乏。
本研究旨在明确免耕（no tillage，NT）与常规耕作（conventional tillage，CT）对两类SPQ指标时间动态变化的影响：其一为容量型SPQ指标，包括容重（bulk density，BD）、大孔隙度（macroporosity，Pmac）、空气容量（air capacity，AC）、植物有效持水量（plant available water capacity，PAWC）、相对田间持水量（relative field capacity，RFC）、德克斯特指数（Dexter's S）以及结构稳定性指数（structural stability index，SSI）；其二为动态型SPQ指标，涵盖田间饱和导水率（field saturated hydraulic conductivity，K0）、导水大孔隙度（water-conducting macroporosity，εma）、中孔隙度（mesoporosity，εme），以及基于总孔隙水通量的孔隙连续性指数（CWTP）、大孔隙水通量孔隙连续性指数（CWmac）和中孔隙水通量孔隙连续性指数（Cwmes）。
此外，本研究还评估了土壤管理体系对玉米产量的影响。研究在玉米生育期内的4个关键时段/种植阶段开展了测定与分析：播前期（before seeding，BS）、六叶期（six leaf stage，V6）、生理成熟期（physiological maturity，R5）以及收获后（after harvest，AH）。
容量型SPQ指标通过采用砂箱与压力室测定的土壤持水曲线推导得出，而动态型SPQ指标则基于使用盘式张力入渗仪测得的田间入渗数据计算得到。多数容量型SPQ指标会受采样时段/种植阶段的影响，但两种耕作处理下的指标变化趋势相近、数值相当，尤其在AH阶段表现最为显著。
动态型SPQ指标在生育期内的变化规律则因土壤管理体系不同而存在明显差异。在NT处理下，多数动态指标从BS至V6阶段呈上升趋势，至AH阶段再度下降；而在CT处理下，其变化趋势则截然不同：从BS至V6阶段呈下降趋势，直至R5阶段保持稳定，至AH阶段再度上升。
CT处理下的玉米产量更低（NT：10939 kg·ha⁻¹；CT：8265 kg·ha⁻¹）。本研究结果表明，在评估耕作体系以开展作物产量建模时，需纳入动态型SPQ指标及其时间动态变化特征。而容量型SPQ指标无法区分两种耕作处理间的差异。