Nitrogen‐15‐Determined Nitrogen Fixation in Field‐Grown Chickpea, Lentil, Fababean, and Field Pea¹

Abstract

Field‐determined estimates of N2 fixation by 15N isotope dilution have not been determined in irrigated annual grain legumes in North America. Nor does knowledge exist as to which nonfixing control plants are most appropriate for these grain legumes when using 15N isotope dilution methods. Within a crop species grown on two Typic Haploboroll soils for 2 yr, lentil (Lens culinaris Medik), fababean (Vicia faba L. minor), and pea (Pisum sativum L.) cultivars adapted to western Canada did not differ in their ability to benefit from symbiotic N2 fixation. When inoculated, N2 fixed averaged 176,84, 216, and 185 kg N ha−1 for chickpea (Cicer arietinum L.), lentil, fababean, and pea, respectively. The percent plant N derived from the atmosphere averaged 82, 67, 85, and 79%, respectively, for the same crops. Response to inoculation was dependent on the crop even though all were infected by Rhizobium leguminosarum Uninoculated chickpea had no nodules or N2‐fixing activity. Inoculation increased N2 fixation in fababean by 19 to 67% and in lentil by 5 to 16% depending on the site. There was a response to inoculation in pea at only one of the two sites. The presence of indigenous soil R. leguminosarum precluded the use of uninoculated treatments as nonfixing controls (except for chickpea) for estimating N2 fixation by 15N isotope dilution. Barley (Hordeum vulgare L. ‘Galt’) or wheat (Triticum aestivum L. emend. Thell ‘Columbus’) appeared to be appropriate control plants for these grain legumes. Because the 15N‐determined fertilizer use efficiency of these controls was similar to that of the N2‐fixing legumes, estimates of N2 fixation by N balance were not significantly different from those obtained by 15N isotope dilution.

Fall vs. spring rhizobial inoculation of chickpea

“…Despite variability, the Nfixation levels were comparable with those reported for chickpea in other studies (Rennie and Dubetz 1986;Peoples et al 2001). At Young, levels of %Ndfa and N 2 fixed by the inoculated plants were high, and no significant differences were observed among the inoculant treatments.…”

Response of pea to rhizobia inoculation and starter nitrogen in Alberta

“…Median seed N yields ranged from 23 to 246 kg N ha -1 ( Table 2). Assuming that 75% of pea N was present in the seed at harvest (Rennie and Dubetz 1986;Armstrong et al 1994), the median deficit in soil NO 3 -N compared to the amount of N taken up by pea was 150 kg N ha -1 ; values ranged from 0 to 266 kg N ha -1 ( Table 2). Processes that will reduce this deficit include continued soil N mineralization and the presence of available soil N at depths greater than 30 cm, while losses and incomplete uptake of available soil N will increase this deficit.…”

Dinitrogen Fixation of Lentil, Field Pea and Fababean Under Dryland Conditions

“…Each microplot was I m x 0.225 m in area, and contained one planted row. The urea solution (1.51 microplot ') was injected at 10-cm increments in the soil adjacent to the planted row using an adjustable dispenser and an 18-gauge needle which was 10 cm in length (Rennie 1986 "N enrichment than wheat, but it was not possible from the data collected to determine which was more appropriate. Thus, the average of both barley and wheat samples was Coefficients ofcorrelation are sisnificant at *P < 0.05 and **P < 0.01. and 216 kg N ha t y.-t, respectively (Rennie and Dubetz 1986), indicating that moisture was probably still limiting for pea and fababean at the wettest sites in this study.…”