Table 3. Analysis of variance results on effects of genotype, irrigation, their interaction (for the field experiments), presence of hardpan, and it’s interaction with genotype (for the controlled environmental experiments) for various traits measured in the study.

The field level measurements of root and shoot traits (total and fine root length, surface area, and volume, and shoot and root dry weights) were made only at one location (Florence, SC, USA).

Trait	Genotype	Irrigation†	Genotype x Irrigation	Hardpan‡	Genotype x Hardpan
Field conditions
Yield§ (Florence, SC) (Kg m-2)	< .0001	0.0005	0.0449	N/A	N/A
Yield (Pendleton, SC) (Kg m-2)	< .0001	0.0074	0.9490	N/A	N/A
Total root length (cm)	0.0904	0.0413	0.9732	N/A	N/A
Total root surface area (cm2)	0.0013	0.1026	0.4274	N/A	N/A
Total root volume (cm3)	0.0322	0.0418	0.4229	N/A	N/A
Fine root¶ length (cm)	0.3205	0.0011	0.9897	N/A	N/A
Fine root surface area (cm2)	0.2864	0.0008	0.9939	N/A	N/A
Fine root volume (cm3)	0.2548	0.0006	0.9957	N/A	N/A
Shoot dry weight (g m-2)	0.0005	0.0473	0.7707	N/A	N/A
Root dry weight (g m-2)	0.2756	0.0214	0.1006	N/A	N/A
Controlled environmental conditions
Total root length (cm)	0.0149	N/A	N/A	0.2690	0.5155
Total root surface area (cm2)	0.0050	N/A	N/A	0.2613	0.6925
Total root volume (cm3)	0.0055	N/A	N/A	0.1747	0.8554
Fine root length (cm)	0.0067	N/A	N/A	0.1628	0.4425
Fine root surface area (cm2)	0.0099	N/A	N/A	0.1863	0.4856
Fine root volume (cm3)	0.0136	N/A	N/A	0.2050	0.5196
Shoot dry weight (g)	0.0014	N/A	N/A	0.1236	0.2324
Root dry weight (g)	0.0029	N/A	N/A	0.1908	0.2460
Water use (kg)	0.2083	N/A	N/A	0.2575	0.6071
Water use efficiency# (g kg-1)	0.0102	N/A	N/A	0.3460	0.5133

^†At Florence, 25.4 mm water was applied at 35, 56, 69, 76, and 83 days after planting [DAP]. At Pendleton, 25.4 mm water was applied at 102 DAP.

^‡In the controlled environmental experiments, a synthetic hardpan (1 cm thickness) that simulate a compacted soil layer was imposed at 25 cm depth in half of the plant growth columns to test the genotypes for water use efficiency under the presence and absence of a hardpan.

^§Yield was measured at two locations (Florence and Pendleton) in SC, USA in 2017.

^¶Diameter < 0.25 mm.

^#Ratio between the amount of aboveground biomass produced and water used during a 40-day growth period.