Improving P-efficiency in Crops Through the Management of Highly Effective Beneficial Soil Microorganisms

Research indicates that the diversity of arbuscular mycorrhizal (AM) fungi in the Canadian Prairies has been negatively impacted by crop production practices such as the use of fallow and the prevalence of small grain cereals in rotation. The functionality provided by the original diversity of AM fungi to crop P nutrition has been reduced. Including a pulse crop such as lentils in rotation, along with inoculation of this crop with highly effective AM fungal isolates may be a good strategy to increase the functionality of the AM symbiosis of crop plants and increase the sustainability and profitability of agriculture.

We now have tools to assess the abundance of various AM fungi in soils. We are completing the evaluation of the functionality of 49 Prairie native AM fungal isolates to be used as crop inoculates to improve P use from soils. We also have isolates of native plant growth-promoting rhizobacteria (PGPR) that are closely associated with both pulse crop roots and AM hyphae. These 140 isolates are highly effective P-solubilizing microorganisms and could be used along with the AM inoculants for the Prairie. We can produce a technology that reliably improves the P-efficiency of a cropping system using the ability of plants to collaborate with microbial associates. Farmers including both organic and conventional growers are interested in making more efficient use of P in crop soils. A previous survey conducted in the Prairies shows that wheat is P-limited in 57% of the organic fields in best years, and from the IPNI 2010 North America Soil Test Summary, 82% of conventionally farmed soils in Saskatchewan are below critical soil test levels, and may benefit from additions of soluble P fertilizer to improve crop yields. These innoculants could also be used to improve the use of applied P fertilizers.

Work in the first year of this study has went well, further evaluation of both AM fungi isolates and associated PGRP bacteria isolates has resulted in choices as to which isolates to include in seed inoculations for field experiments in years 2015, 2016 and 2017. The overall project objectives include the following: to raise the efficiency of P use by crops through 1) the development of innoculants combining highly effective AM fungal strains and companion PGPR and P-solubilizing microorganisms, and 2) the identification of agronomic practices to improve rhizosphere community function.