Effect of formulation and placement of Mesorhizobium inoculants for chickpea in the semiarid Canadian prairies

The use of bacterial inoculants can increase root nodulation and the seed yield of annual legumes. A six site-year study was conducted to determine the effect of formulations (peat-based powder vs. granules) and placement in the soil (seed-row vs. side-band) of Mesorhizobium inoculants on plant establishment and seed yield of chickpea (Cicer arietinum L.) in the semiarid Canadian prairies. Two market classes of chickpea, namely desi and kabuli, were grown on silt loam and heavy clay soils in southwestern Saskatchewan from 1999 to 2002. Inoculation reduced plant population by 10% for desi chickpea, but had no effect on kabuli chickpea. However, the use of inoculant increased seed yield by an average of 35% for desi chickpea and 7% for kabuli chickpea. On the heavy clay, soil inoculation increased seed yield by 16% for desi and 9% for kabuli compared with seed inoculation, whereas the yield increase due to soil inoculation, over seed inoculation, was 3% when the crops were grown on the silt loam. Granular inoculant applied in the seed row produced similar seed yields to side-banded inoculant. Inoculation delivery systems had a marginal impact on plant height, with no effect on the lowest pod height from the soil surface or days to maturity. Regardless of placement, soil inoculation with a granular form of Mesorhizobium was preferred over seed inoculation because of its greater positive impacts on plant establishment and seed yield for both desi and kabuli chickpea in this semiarid region. Key words: Cicer arietinum, seed weight, heavy clay, silt loam, harvestability