Improving Nutrient Uptake in Organic Dryland Wheat Cropping Systems through Cultivar Specific Interaction with Azospirillum.

Obtaining sufficient plant available nitrogen (N) in organic dryland wheat cropping systems is difficult. Plant root association with beneficial bacteria that actively fix N is one alternative that can help supplement N needs in low-input systems. This study was conducted to determine whether inoculation with Azospirillum could improve nitrogen uptake and increase crop yield, whether differences exist in the ability of wheat cultivars to benefit from inoculation of these diazotrophic bacteria, and the impact of N availability on this beneficial interaction. Seed from ten historic, ten modern and ten wheat cultivars from the advanced organic breeding program were either left untreated, or treated with a commercial inoculant of Azospirillum, and planted at thee locations under certified organic management, and two locations under conventional management. Preliminary results indicated that in one certified organic location with lower fertility, inoculation significantly increased yield and protein, and clear differences existed among individual cultivars in response to the inoculant. In another location with higher fertility, none of the cultivars responded as favorably to the inoculant, and yield in some cultivars was reduced. Plant breeders should be able to select for beneficial cultivar interactions with Azospirillum to increase wheat yield and protein levels. On-going research will determine the impact of site-specific soil conditions on the effectiveness of Azospirillum in organic and conventional systems.