Symbiotic N₂-Fixation Estimated by the ¹⁵N Tracer Technique and Growth of Pueraria phaseoloides (Roxb.) Benth. Inoculated with Bradyrhizobium Strain in Field Conditions

Table 4

Soil N status in inoculated and noninoculated Pueraria and Ipomoea plots at harvest.

Treatments	OrgC	N	C/N	Total N	Ndfs		Ndfa		Ndff		N imb.	N loss
	%			g/m^2	%	g/m^2	%	g/m^2	%	g/m^2	%	%	g/m^2
I. Pueraria	3.08	0.212	14.52	18.33	91.77a	16.90	4.15	0.68	4.08	0.74	37.0	57.12	1.14
NI. Pueraria	3.00	0.209	14.33	17.88	94.80b	16.95	1.14	0.21	4.07	0.73	36.5	60.05	1.2
Ipomoea	2.98	0.214	13.95	19.55	95.84b	18.74	—	—	4.16	0.81	40.5	55.73	1.12
Sign. Trait ()	ns	ns	ns	ns		ns	ns	ns	ns	ns	ns	ns	ns

I. Pueraria = inoculated Pueraria, NI. Pueraria = noninoculated Pueraria, Sign. Trait = significant trait at 5% probability level, and ns = nonsignificant; significant at . Composite soil samples were collected from each plot at harvest and subjected to chemical analysis for organic carbon (OrgC; %), N (%), and ¹⁵N atom% excess using the methods described in the text. Following that, (3), (6), (7), or (8) in the text was used to calculate soil Ndff (%), Ndfa (%), and Ndfs (%). Soil total N is the average N in treatments at the end of the trial and has three origins (Ndfs = soil nitrogen derived from soil, Ndfa = soil nitrogen derived from atmosphere, and Ndff = soil nitrogen derived from fertilizer). Total N is calculated based on (10) in the text. N imb. = N immobilization (it corresponds to the percentage of the fertilizer N that remains in the soil at the end of the experiment out of the initially applied 2 g/m²; cf. (11)). One-way ANOVA was performed using CropStat ver. 7.2. N loss is the fertilizer nitrogen lost in the system during the experiment via denitrification or leaching or volatilization.
In a column, values with different letters (a, b) are statistically different at the indicated significant trait.