Update:
Objective 1 – modeling
Regarding the modeling part of the project, during the reporting period (October to December 2018) the ISU team finalized the 2018 soybean predictions and post-season analyses. We found that the 2018 yield forecasts were accurate in most but not in all locations. Issues that caused the over/underestimation of yield in some locations were excessive moisture impacts on crop staging and leaf N concentration and also pod/seed loss from physiological maturity to harvest due to extremely wet conditions. In terms of crop roots and soil water and nitrogen, model predictions were very accurate.

Objective 2 – field experiments
Regarding to field trials, during the reporting period (October to December 2018) we harvested the three field experiments and processed plant and soil samples for nitrogen and carbon concentrations and other measurements. Further, we performed data analysis and presented some of the results at the ICM conference. In brief, in 2018 we have had three field trials located in central, northwest and southwest Iowa. Each trial had normal and high input management treatments. The high input management included irrigation and N-fertilization applications in addition to higher pre-planting PK fertilization rates. In central Iowa narrow rows were used for the high input management. More than 5 irrigations applied at the SE site to offset the water deficit occurred in summer of 2018. In central and NW sites much fewer irrigations were applied because of the above normal precipitation occurred in summer of 2018. In SE Iowa, we got the larger response to high-input management (yield benefit of 7 bu/ac; 59.3 vs 66.8 bu/ac). In that site, the plants were very big. In the other two sites, we did not observe a yield substantial yield benefit neither a yield loss.