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Fluid Journal : Winter 2018
8 The Fluid Journal Winter 2018 Dr. Below is Professor, Dr. Beyrer is Research Specialist, and Mrs. Seebauer is Sr. Research Specialist in the Department of Crop Sciences, University of Illinois, West Gregory Drive, Urbana, IL 61802, and Dr. Bender is Sr. Agronomist, the Mosaic Company Cleveland, WI. (Table 4). In contrast in 2016, by providing half fertilization preplant, a 50 percent delay in fertigation resulted in a 52 bu/A decrease in yield. Planting population did not change the overall results of either fertility program (Table 4). Notably, the 100% rainfed yields were similar to the fertigated yields of 2015, using less fertilizer. Individual corn hybrid yields varied by 25 to 26 bu/A in both fertility scenarios but there were varietal differences (Table 5). The greatest yields in the 100% preplant control plots were produced by 7087VT2P and N74R-3000GT, while the greatest yields in the delayed fertigation were produced by DKC64-87 and 8621VT2PRIB (Table 5). These yield decreases were due to the 10% decreases in both kernel number and kernel weight (daa not shown). Decreases in kernel number may be due to plant stresses before pollination. Potentially, the delay in N availability from fertilization in combination with the depth of the SDI system below the root zone, led to an early nutrient deficiency that was unrecoverable. However, these findings also indicate that some hybrids are more suited to fertigation and can better take advantage of the timed nutrient supply to produce greater yields with more efficient nutrient use. Summing up Using a subsurface drip irrigation system to precisely deliver supplemental fertilizer to the root zone successfully increased yields in both corn and soybeans in central IL up to by 52 bu/A for corn, depending on the hybrid. Supplying only half of the fertilizer preplant in 2016 led to yield losses, even when supplying the remainder throughout the growing season via fertigation. Typically, a greater planting population is necessary for increasing yields, however, the weather in all three years (2014 to 2016) enabled corn to maximize yield even at a population of 32,000 plants/A. Fertigation by SDI resulted in hybrid and variety yield differences, which suggests a need for characterization of optimal genetics and optimal nutrient supply scheduling for enhanced nutrient use and additional yield improvement. Acknowledgements: The authors would like to acknowledge the generous support of numerous partners that helped make this research possible, including the Fluid Fertilizer Foundation, A & L Great Lakes Laboratories, AgVise Laboratories, BASF, John Deere, Mosaic, Monsanto, Netafim, Syngenta, USDA-NIFA project NC1200, Ward Laboratories, Inc., and Winfield United.