Table 2.

Effect of mycorrhizal inoculation (AMF), date of inoculation (days after seeding), and nitrogen (N) form on fresh mass (FM), dry mass (DM), and dry matter content (DMC) of onion plants (cv. Stuttgarter Riesen) analyzed after a growing period of 149 days in a three factorial ANOVA based on an orthogonal design with six replications. Means ± standard deviation followed by the same letter do not differ significantly according to Duncan’s multiple range test. Probability levels written in italics indicate significant differences at a significance level of α = 0.05

AMF (v/v %)	Date (days)	N form	FM (g plant−1)	DM (g plant−1)	DMC (gkg-1)
0			45.7 ± 8.5 a	6.84 ± 1.7 a	14.8 ± 1.2
0.3			40.6 ± 9.6 b	5.91 ± 1.8 b	14.4 ± 1.8
3.0			43.5 ± 10.2 ab	6.43 ± 2.0 ab	14.6 ± 1.5
	0		42.3 ± 9.9	6.22 ± 1.9	14.5 ± 1.5
	65		44.2 ± 9.4	6.57 ± 1.8	14.7 ± 1.6
		NO3 –a	49.9 ± 7.1 a	7.89 ± 1.2 a	15.8 ± 0.64
		NH4 +b	36.7 ± 6.9 b	4.90 ± 1.0 b	13.4 ± 1.2
0		NO3 −	51.4 ± 6.1c	8.07 ± 1.3c	15.0 ± 0.79 ac
0.3			46.8 ± 8.3	7.46 ± 1.2	16.0 ± 0.61 a
3.0			51.6 ± 6.4	8.18 ± 1.2	15.8 ± 0.48 a
0		NH4 +	40.4 ± 7.2	5.71 ± 1.2	14.0 ± 0.91 b
0.3			34.4 ± 6.7	4.36 ± 0.65	12.8 ± 1.2 c
3.0			35.2 ± 5.8	4.63 ± 0.55	13.3 ± 1.2 c
Source of variation			Probability level
AMF			0.044	0.014	0.364
Date			0.253	0.175	0.252
N form			< 0.001	< 0.001	< 0.001
AMF × date			0.492	0.448	0.505
AMF × N form			0.336	0.108	0.010
Date × N form			0.502	0.550	0.617
AMF × date × N form			0.275	0.737	0.312

^aNO₃ ⁻ predominant = 95% NO₃ ⁻/5% NH₄ ⁺

^bNH₄ ⁺ predominant = 25% NO₃ ⁻/75% NH₄ ⁺

^cOnly the results of the AMF × N form interaction are presented averaged over the dates