Rhizobial inoculant formulations and soil pH influence field pea nodulation and nitrogen fixation

Abstract

. Rhizobial inoculant formulations and soil pH influence field pea nodulation and nitrogen fixation. Can. J. Soil Sci. 80: 395-400. Crop production systems that include field pea (Pisum sativum L.) in rotation are important for sustainable agriculture on acid soils in northwestern Canada. Greenhouse experiments were conducted to compare the ability of liquid inoculant applied to the seed, powdered peat inoculant applied to the seed, and granular inoculant applied in a band with the seed to establish effective nodulation on field pea grown at soil pH(H 2 O) 4.4, 5.4 and 6.6. Plants were grown to the flat pod stage, and then total plant biomass dry weight, dry weight of nodules, number of nodules, plant nitrogen content, and proportion of plant nitrogen derived from the atmosphere (%Ndfa) were measured. Granular and powdered peat inoculants produced greater nodule numbers and weight, plant nitrogen content, %Ndfa and total biomass than liquid inoculant in at least two of the three experiments. Only granular inoculant was effective in establishing nodules at soil pH 4.4, but granular and powdered peat inoculants were effective at pH 5.4, and all three formulations were effective at pH 6.6. The results showed that granular inoculant has potential for effective nodulation of field pea grown on acid soil. . Les plantes étaient cultivées jusqu'au stade de la gousse plate, après quoi on mesurait le poids sec total de la biomasse, le poids sec des nodosités, la teneur en N de la plante et la proportion de N provenant de l'atmosphère (%Nat). Les inoculants sur tourbe, granulés ou pulvérulents donnaient des nodosités plus abondantes et plus lourdes ainsi qu'une teneur en N de la plante, un %Npat et une biomasse totales plus élevés que la présentation liquide. Dans au moins deux des trois expériences, seul l'inoculant granulé réus-sissait à produire des nodosités viables au pH 4,4, mais au pH 5,4 les deux inoculants sur tourbe étaient efficaces et au pH 6,6 les trois présentations l'étaient toutes. Il découle de ces observations que l'emploi d'un inoculant granulé peut garantir une nodulation viable chez le pois cultivé en sols acides.

Inoculant formulation and fertilizer nitrogen effects on field pea: Nodulation, N2 fixation and nitrogen partitioning

“…nodule numbers and weight, plant nitrogen content and total biomass in field pea than liquid inoculant in at least two of the three greenhouse experiments (Rice et al 2000) The total N accumulated in field pea plants was in the order: granular inoculant > peat inoculant > liquid inoculant = uninoculated (Table 5). Total N accumulation was 21 to 63% higher from inoculated pea compared with uninoculated pea at 5 of 6 site/years (Table 5).…”

“…A composite soil sample (0-15 cm depth) was taken each year from each site prior to planting for enumeration of indigenous Rhizobium leguminosarum bv. viciae using the most probable number (MPN) plant grow out method (Rice and Olsen 1993). These counts and other soil characteristics of the sites are shown in Table 1.…”

“…Nitrogen accumulation was estimated by multiplying N concentration by DM yield. Nitrogen fixation was estimated by the difference method (Rice and Olsen 1993), using canola as a nonfixing control. The total N accumulation in pea minus the total N accumulation in canola determined the difference.…”

“…They showed that the biomass N, total N, and N 2 fixation of field pea were increased with soil inoculation compared to conventional methods of seed application. Improved inoculant formulation and delivery systems have the potential to improve nodulation and N 2 fixation, particularly under stress conditions (Graham and Chatel 1983;Smith 1992;Evans et al 1993). Under field conditions, greater N 2 fixation can be achieved when efficient rhizobia strains are supplied to both the crown and lateral root areas, rather than the crown root area alone (Wolyn 1989).…”

“…This has been done either directly (in liquid formulation) or, usually, by first impregnating the Rhizobium in peat (peat formulation) and applying it to the seed (Smith 1992;Hynes et al 1995;Stephens and Rask 2000). Although seed inoculation is widely practised, there are several situations in which it may be an inefficient means of inoculation: e.g., on seed dressed with a pesticide incompatible with rhizobia, for seeds such as peanuts which are too fragile for seed-surface inoculation, or when higher inoculation rates than can be seedapplied are necessary (Brockwell et al 1980).…”