The study also shows that porosity, macroporosity, and coarse
mesoporosity values increased in the third depth zone (20- to 30-cm),
especially in the RC treatment and also within the GB treatment as
compared to the 10- to 20-cm depth. Comparing effects of genetic soil
horizons on soybean root distribution in the claypan region, Myers et
al. (2007) observed that soybean root growth was inhibited in the E
horizon but stimulated in the claypan. Their study showed that the
minimum root length occurred in the horizons just above the claypan
(E or EB horizons) and root length increased within the argillic (Bt)
horizon. Root diameters were smaller below the claypan. These
differences were attributed to the availability of nutrients, soil pH, and
aluminum concentrations.