AMES, Iowa, March 4 -- Iowa State University issued the following news release: * * * Ideal nitrogen fertilizer rates in Corn Belt have been climbing for decades, study shows AMES, Iowa - The amount of nitrogen fertilizer needed to maximize the profitability of corn production in the Midwest has been increasing by about 1.2% per year for the past three decades, according to new Iowa State University research. The study, published last month in Nature Communications, analyzed data from prior  more PR