NItrogen Loss in 2008 From Midwestern Corn Fields.

Much of the U.S. corn belt received over 40 cm of precipitation from April through June 2008. Based on visual surveys in August (1500 aerial photographs, 2000 road miles), this rainfall appeared to cause widespread N deficiency in the corn crop. My back-of-the-envelope estimate is that 460 million bushels of potential corn yield were lost due to N deficiency in 2008. Abundant summer rainfall supported good yields that could have been better if N had not been limiting. Sidedress applications delivered N to the crop more effectively than preplant applications. Available evidence suggests that much of the lost yield potential could have been recovered with rescue N applications. Aerial imagery offers an excellent tool to assess the need for rescue N. I estimate that about 14 million acres would have responded profitably to rescue N applications in 2008. Logistics of application and of delivering the fertilizer are obstacles, but lack of decision tools and planning may be the biggest obstacles.