2.2. Experimental design
Exp. 1 was a randomized complete block design with three
replicates. Four plant spatial configuration modes (TPG, equidistant
row planting geometry (ERPG), twin row planting geometry
(TRPG), and seedling throwing planting geometry (STPG)) were
randomly assigned. There were twelve plots in total with a plot area
of 22.5 m2 (5.0 m
×
4.5 m). In the TPG group, three single seedlings
were arranged in an equilateral triangle with a side length of
10.0 cm. This arrangement formed an individual hill, which was
separated from adjacent hills by a spacing of 41.7 cm
×
40.0 cm. In
the TRPG condition, seedlings were transplanted at a hill spacing
of 40.0
×
16.7 cm and 26.6 cm
×
16.7 cm for wide row and narrow
row, respectively. Each hill contained a single seedling. Similarly,
the ERPG group had seedlings which were transplanted at a hill
spacing of 33.3 cm
×
16.7 cm with a single seedling per hill. Finally,
in the STPG condition, seedlings were randomly thrown with a density
of 18.0
×
104 plants ha−1 (Fig. 2). All of the above four planting
geometries maintained a constant planting density of 18.0
×
104
plants ha−1.
The experimental design of Exp. 2 was the same as that of Exp.
1. Exp. 2 was under a conventional-tillage (CT, e.g. plowing plus
two harrowing) system while Exp. 1 was under a zero-tillage (ZT)
system.
In Exp. 3, the treatments were imposed as two factorial
experiment, arranged in randomized complete blocks with three
replications and a plot area of 15.0 m2 (5 m
×
3 m). The two manipulated
factors were rice variety (C498, G188, Y203 and C6203) and
plant spatial configuration (TPG, TRPG and STPG). The implementation
of all three planting configurations was identical to those in
Exps. 1 and 2.
The experimental design of Exp. 4 was the same as that of Exp.
3, but was located in a different geographical region (Santai as
opposed to Wenjiang). Both Exps. 3 and 4 were conducted under
the CT system. Additionally, all tested varieties were sown on April