*2.2. Experimental Setup and Treatment Details*

The field experiment was implemented for two wet seasons (2014 and 2015) and was laid out in a split–split plot design with three replicates. In this experiment, seedling age at the time of transplanting (SA) was assigned as the main plot, seedling density (SD) as the subplot, and variety (V) as the sub-subplot. Four levels of SA were used: 15 (SA15), 25 (SA25), 35 (SA35), and 45 (SA45) d-old seedlings; three levels for SD: One (SD1), three (SD3), and five (SD5) seedlings per hill; and three different waxy or glutinous varieties: IRUBN0300–63–5–4 (V1), TDK10239–SSD4–303–1 (V2), and TDK-8 (V3). V1 was considered a high-tillering variety, while V2 and V3 were relatively low and medium tillering varieties, respectively. V3 (TDK-8) is a variety widely grown in southern Lao PDR because of its good eating quality (used as check variety in this experiment), while V1 and V2 were two of the most promising waxy rice varieties tested at ARC. A total of 108 plots (4 SA × 3 SD × 3 V × 3 replications) were established in each year of the field experimentation, with a sub-sub plot size of 12 m2 (2 m <sup>×</sup> 6 m). Only the main plot (SA) was separated by bunds, but a buffer space of about 0.5 m was established in each sub-subplot.

The experimental field was the same for both years and was prepared with one dry plowing (after all crop residues were removed from the field), followed by land soaking and two wet harrowing operations to achieve thorough puddling in each year. Bunds and canals were constructed and plastic linings were installed to 40 cm depth in the sides of the bunds to reduce seepage losses around the main plot. Transplanting schedules were based on seedling age treatments. At a 10 d transplanting interval, SA15 was transplanted first, then followed by SA25, SA35, and SA45 treatments, respectively. Transplanting dates during 2014 were the following: 1 July (SA15), 10 July (SA25), 20 July (SA35), and 30 July (SA45); whereas during 2015, transplanting dates were 2 July (SA15), 12 July (SA25), 23 July (SA35), and 2 August (SA45). Transplanting of seedlings was carefully done at a regular spacing of 20 cm × 20 cm in all treatments to minimize seedling transplanting shock and to allow the plants to recover quickly in the experimental field. The number of seedlings planted per hill varied according to the seedling density treatments (one, three, and five seedlings per hill) of the experiment.
