Dong Wen-cai;Fu Qiang;Wang Quan-jiu;Cao Chang-peng

Northeast Agr Univ, Coll Water Conservancy & Architecture, Harbin 150030, Heilongjiang, Peoples R China;Xian Univ Technol, Inst Water Resources, Xian 710048, Shaanxi, Peoples R China

compensatory growth;plough pans;root characteristics;soybean

Plough pans (PPs), common in the black-soil region of northeastern China, have significant effects on the root systems of crops. We conducted a field experiment to study the distribution of soybean roots under the influence of PPs. The soybean roots showed compensatory growth above the PP, with higher root length and weight in soil with a PP compared to those without a PP. Roots were heavier and longer in the 15-75 cm soil layer without a PP than with a PP. Soil porosity was lower in the PP and the soil below the PP, which likely decreased the oxygen content of the soil and induced more growth of roots above the PP. The PP is also likely to decrease infiltration of rain-water and hinder the migration of nitrate downward, which in turn increased the density and length of soybean root hairs, which, hence, promoted growth.