Managing Global Resources for a Secure Future

Peanut, being a legume, forms a symbiotic relationship with a rhizobia bacteria that is able to fix atmospheric nitrogen, converting it into a form usable by the plant. These rhizobia bacteria can then live for years in the soil, meaning that when peanuts are planted into that same field years later, there is a ‘native’ population of rhizobia available to form the relationship once again. As acreage expands in the state of Mississippi, growers have begun to plant the crop on ground where peanut has not previously been planted, making a supplemental application of rhizobia bacteria crucial to the production of a successful peanut crop. These rhizobia, being living organisms, are sensitive to many outside factors that may inhibit their effectiveness when improperly applied. A set of trials were conducted in both Starkville and Stoneville, MS in 2016 to determine the optimum nitrogen rate and product to apply in the event of a failed rhizobia inoculation. The trial was set up as a six (rate; 33, 66, 99, 132, 165, and 198 kg/ha) by three (product; granular urea, granular ammonium sulfate, liquid urea ammonium nitrate [UAN]) factorial with both a positive (inoculated) and negative (non-inoculated) control. Inoculated plots averaged 2156 kg/ha more than non-inoculated plots. Across application rates, UAN, ammonium sulfate, and urea increased yield by 1640, 1252, and 1120 kg/ha, respectively, when compared to non-inoculated plots. Across products, each unit of nitrogen applied to plots increased yield by 8.9 kg/ha. The only supplemental applications that yielded equal to the inoculated treatment were 132 and 198 lb/acre UAN. Trials will be continued and results will allow growers, Extension personnel, and consultants to make informed decisions when dealing with rhizobia inoculation failure.