How Effective are Granular Inoculants on Irrigated Pea?

Introduction

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Pea is generally considered to be a good nitrogen fixing species capable of supplying a large portion of its N requirements through N fixation when inoculated with an appropriate Rhizobium strain (LaRue and Patterson, 1981). The amount of N derived from fixation in any given year, or any given location, is highly variable and depends on a number of factors including environmental conditions, soil fertility and general crop health (Rennie and Dubetz, 1986; Bremer et al., 1988; Kucey, 1989; Androsoff et al., 1995). Management strategies that maximize nitrogen fixation ultimately contribute to higher pea yields.

Application of commercial inoculants containing Rhizobium leguminosarum biovar viceae with pea seed is one management strategy used to enhance nitrogen fixation. Inoculants are typically applied as peat based powders or
liquid formulations directly to the seed coat prior to seeding. Manufacturers have developed and formulated inoculants as granules.

In the granular form, the Rhizobium inoculant is applied in the soil. When compared with more traditional seed-applied formulations, granular inoculants have been shown to lead to better nodulation and higher seed yields (Bezdicek et al., 1978; Brockwell et al., 1980).