Measurement of Nitrogen Fixation by Soybean in the Field Using the Ureide and Natural ¹⁵N Abundance Methods

Abstract

Nitrogen fixation by field-grown soybean (Glycine max [L.] Merrill) was assessed by the natural '5N abundance and ureide methods. The field sites (five) and genotypes (six, plus two levels of inoculation on Bragg) were chosen to provide a range of proportions of plant N derived from nitrogen fixation (P). Genotypes K466, K468, ntslO07, and ntsIll6 and Davis were included on the basis of their reported tolerance of the suppressive effects of nitrate on nodulation and nitrogen fixation. Bragg was included as a 'nitrate-sensitive' genotype. Seeds of all genotypes were inoculated at sowing with Bradyrhizobium japonicum CB1809 (USDA136). Amounts of nitrate in the soil profile (0-1.2 meter depth) at sowing ranged from 70 (site 3) to 278 kilograms per hectare (site 5), resulting in large effects on plant nodulation, on the 615N values of nodulated plants, on the relative abundance of ureide-N in vacuum-extracted sap (VES) and stem extracts, and finally on the estimates of P. There was no relationship between amount of soil nitrate at sowing and the P15N of the plant-available soil N. Correlation matrices of the measured and calculated parameters indicated generally weak correlations between crop growth (dry matter and N) and the parameters of symbiotic activity (nodule weight, 615N, relative ureide-N); correlations were strong and highly significant between nodulation and the measures of nitrogen fixation (615N, relative ureide-N; r = 0.79-0.92). Estimates of P ranged between 0 and 68% (B15N) and between 6 and 56% (ureide) and were highly correlated (r = 0.97). Results indicated that the ureide method can be used with confidence to assess P by field-grown crops of soybean.

VAMP721a and VAMP721d are important for pectin dynamics and release of bacteria in soybean nodules

“…Plants were fertilized twice weekly with nutrient solution lacking nitrogen (Herridge et al, 1990). Plants were grown in a glasshouse (24-28°C) under long day conditions (16 h : 8 h, day : night).…”

Role of Nitrogen on Growth and Seed Yield of Soybean and a New Fertilization Technique to Promote Nitrogen Fixation and Seed Yield

“…On the other hand, nitrate and amino acids (especially asparagine) are the major transport forms of N absorbed by soybean roots [34,35]. Herridge et al [36,37] developed the "relative ureide method" for evaluating the % Ndfa (percentage of nitrogen derived from atmospheric dinitrogen) by analyzing the concentrations of nitrogen compounds in xylem sap obtained from bleeding sap of a cut stump or by vacuum collection from stems. The concentrations of ureide-N, nitrate-N, and α-amino-N can be determined by colorimetry [38].…”

Characteristics of Nodulation and Nitrogen Fixation in the Improved Supernodulating Soybean (Glycine maxL. Merr.) Cultivar ‘Sakukei 4’

“…Therefore, they have been expected to have high nitrogen-fi xing ability and enhanced productivity, but their growth and yields have been inferior to those of normal genotypes in general (Herridge et al, 1990;Wu and Harper, 1991;Hussain et al, 1992;Pracht et al, 1994;Song et al, 1995;Zhao et al, 1998;Herridge and Rose, 2000). Some super-or hyper-nodulating soybean genotypes showed high nitrogen-fi xing ability only in the early growth stage (Day et al, 1986;Eskew et al, 1989;Wu and Harper, 1991).…”