Testing deep placement of an 15N tracer as a method for in situ deep root phenotyping of wheat, barley and ryegrass

Table 4 ¹⁵N enrichment and root depth of different genotypes

Exp	Species	Genotype	Root depth (m)	¹⁵N enrichment (mg m⁻¹)
Exp	Species	Genotype	Root depth (m)	0.98 m soil depth	1.50 m soil depth	2.02 m soil depth	2.54 m soil depth
1	Winter wheat	Hystar	1.64 a	2.84 a	2.24 a	0.12 a	0.08 a
1	Winter wheat	Tabasco	1.68 a	2.64 a	2.38 a	0.19 a	0.07 a

Exp	Species	Genotype	Root depth (m)	0.67 m soil depth	0.95 m soil depth	1.23 m soil depth	1.52 m soil depth
2	Spring barley	Evelina	1.23 a	2.59 a	2.47 a	2.07 a	1.73 a
2	Spring barley	Laurikka	1.24 a	3.42 a	3.39 a	4.42 a	2.57 a

Exp	Species	Genotype	Root depth (m)	1.09 m soil depth	1.52 m soil depth	1.96 m soil depth	2.39 m soil depth
3	Spring barley	Laurikka	1.21 b	2.62 ab	0.55 a	0.09 ab	0.10 ab
		Kenia	1.26 ab	1.88 ab	0.36 a	0.09 b	0.08 b
		Evergreen	1.29 ab	1.23 b	0.55 a	0.11 a	0.10 a
		Evelina	1.32 ab	2.49 ab	0.58 a	0.10 ab	0.11 a
		Invictus	1.34 ab	1.87 ab	0.48 a	0.11 ab	0.10 a
		Prisma	1.42 ab	3.09 a	0.96 a	0.10 ab	0.10 a
		Tocada	1.48 a	2.05 ab	1.19 a	0.11 a	0.11 a

Exp	Species	Genotype	Root depth (m)	¹⁵N enrichment (atom% excess)
Exp	Species	Genotype	Root depth (m)	0.67 m soil depth	0.95 m soil depth	1.23 m soil depth	1.52 m soil depth
4	Ryegrass	Mercitwo 2 N	1.12 a	0.11 a	0.13 b	0.07 a	0.01 a
		Tetrastar 4 N	1.13 a	0.16 a	0.17 b	0.05 a	0.01 a
		Esquire 2 N	1.14 a	0.15 a	0.10 b	0.02 a	0.01 a
		Fabian 4 N	1.16 a	0.17 a	0.41 a	0.04 a	0.03 a

¹⁵N enrichment was measured at four soil depths from four intervals (i.e., 0.87–1.08 m, 1.39–1.61 m, 1.91–2.13 m, and 2.44–2.65 m in Exp. 1, 0.53–0.81 m, 0.81–1.09 m, 1.09–1.37 m, and 1.37–1.66 m in Exp. 2 and Exp. 4, and 0.87–1.30 m, 1.30–1.74 m, 1.74–2.17 m and 2.17–2.61 m in Exp. 3). Root images were taken by minirhizotron camera on 18 May in Exp. 1 and 3 June in Exp. 2 in 2016, and 21 June in Exp. 3 and 23 May in Exp. 4 in 2017. Root depth was defined as the deepest soil depth in these images where the roots were observed. Different lowercase letters indicated significant genotypic differences at P < 0.05

ISSN: 1746-4811