Management of a Soybean Crop to Maximize a Following Rice Crop's Profit.

The cost of nitrogen (N) fertilization for a rice (Oryza sativa) producer is a determining factor in the profit returned from a rice crop. In 2016, 68% of the rice grown in Arkansas was grown in rotation with soybean (Glycine max), the leading crop in both profit and acres harvested in the state (Hardke, 2017). Variety selection and management of the soybean crop may influence soil-N credits returned to the soil and ultimately the N rate needed to maximize yield in the successive rice crop. A rice crop's performance and input cost is strongly related to the plant-available N. The potential to reduce the amount of N fertilizer required by the rice through management of the previous soybean crop could provide savings with no additional input cost to a rice producer. The total N uptake (TNU), yield, and soil-N credits developed were measured in four maturity groups (MGs) of soybean. A single cultivar of rice followed all four MGs to compare the rice TNU and yield between previous MGs and N rate applied as a single pre-flood treatment of urea. The results from the 2016 soybean crop and 2017 rice crop show no significant difference between soybean MG grown and rice yield (P = 0.9502). There was no significant difference (P = 0.8067) in plant-available N between previous MGs the following spring, nor was there a significant difference between previous MG and rice total N uptake (P = 0.9677). The preliminary data suggest MG of soybean alone does not have an impact on a following rice crop's success under the conditions of this initial year's study. Further research will be conducted to evaluate the impact of soybean planting date on a following rice crop. [ABSTRACT FROM AUTHOR]