Allison Aubert, Wheat State Agronomy Club, Manhattan, KS and Kraig L. Roozeboom, Agronomy, Kansas State University, Manhattan, KS
The efficient management of nitrogen (N) fertilizer and irrigation is of utmost importance. This project was conducted to determine if yield and efficiency of N fertilization in corn could be improved by applying N at later developmental stages through a subsurface drip irrigation (SDI) system. Experiments in 2014 and 2015 compared a Preplant Surface application that injected fertilizer in bands below the residue at planting, to four versions of SDI fertigation that differed in timing and total amount of N applied. The SDI Sidedress treatment concluded at tassel stage (VT). The SDI Maximum treatment supplied an additional 40 pounds of N acre-1 through blister stage (R2). The SDI Sensor treatment received N fertigations after V10 stage only if the ratio of the SPAD (chlorophyll) meter readings from the SDI Sensor plot to the Reference plot was less than 95%. The Reference treatment received both the surface band injections and all SDI fertigations for total seasonal N application that exceeded crop N requirements. The Reference treatment produced up to 32 bushels acre-1 more grain than the Preplant Surface treatment, but averaged only 0.7 bushels of grain pound-1 of N fertilizer. The SDI Maximum treatment averaged slightly less grain yield than the reference treatment, but produced 1.15 bushels of grain pound-1 of N fertilizer. The SDI Sidedress and SDI Sensor treatments resulted in 16 bushels acre-1 more than the Preplant Surface treatment. The SDI Sidedress treatment used N fertilizer most efficiently, producing 1.3 bushels of grain pound-1 of N fertilizer. Applying N into the reproductive stages of corn increased yield, but N fertilizer was used most efficiently when N applications were completed by VT. The use of the SPAD sensor to determine later N applications reduced fertilizer input but resulted in fertilizer use efficiency similar to the SDI Maximum treatment.