Wednesday, November 7, 2007
297-5

Nitrogen Management of Corn with Subsurface Drip Irrigation.

David Tarkalson, USDA-ARS, 3793 North 3600 East, Kimberly, ID 83341 and Jose Payero, Queensland Department of Primary Industries and Fisheries, Tor St, PO Box 102, TOOWOOMBA, Q 4350, Toowoomba, Australia.

The use of subsurface drip irrigation (SDI) for row crops is increasing in the U.S.  One of the potential advantages of SDI is the ability to ‘spoon-feed’ nutrients such as nitrogen (N) to crop roots.  This three-year study assessed N application rates and methods for use with SDI under continuous corn grain production.  Treatments consisted of three N rates (114, 166, ad 248 kg N ha-1) and two N application methods (early season and in-season).  Each treatment was replicated four times in a randomized complete block design.  The early season N applications were applied (knifed) as ammonium nitrate 10 cm below the soil surface midway between the rows within two weeks after planting.  The in-season N applications were all applied periodically through the SDI system as UAN solution (32% N). Grain yield, plant nitrogen uptake, and residual soil nitrate were measured.  Compared to the grain yields from the early season application method, grain yields from the in-season application method were similar in 2004 but 4.6% and 9.9% greater in 2005 and 2006, respectively. At the end of the study the in-season application method had higher nitrate-N masses in the 0 to1.8 m soil profile compared to the early season application method.  Compared to the chlorophyll meter readings in 2006 from the in-season application method, readings for the early season application method were greater for vegetative growth stages but lower for the R3 stage, indicating that N was potentially a limiting factor in the early-season application method treatment during grain development.   Data suggest that the early season application method had greater losses of nitrate-N below the root zone compared to the in-season application method, and these losses may have reduced grain yields.  Compared to one-time nitrogen fertilizer applications, properly scheduled N application to the root zone through SDI systems can increase N use efficiency and grain yield of corn, thus reducing fertilizer costs and reducing potential nitrate losses below the root zone.