2. Materials and methods
2.1. Test soil and soil bins
The test loess soil was collected from farmland in Qingjian County
(E 109°52′, N 37°03′), Yulin city in Shaanxi Province, China. The soil
was passed through a sieve with 10 mm × 10 mm openings and then
air-dried to about 6% of water content in mass. Finally, it was
thoroughly mixed to minimize variability and packed into soil bins
in seven 10-cm deep layers to achieve a natural bulk density of
around 1.35 g cm−3
. Each layer was lightly raked before packing
the next layer to minimize discontinuities between layers. Table 1
gives selected physical properties of the test soil.
The soil bins in this experiment measured 200 cm × 80 cm × 80 cm
with four wheels to facilitate transportation (Fig. 1A). According to previous
studies the roots of 3-year-old jujube trees are distributed mainly in