BC4 FRONT COVER REV3.indd

Nitrogen fertilization is essential for optimizing crop yields and economic returns in irrigated cropping systems in the Central Great Plains area of the USA. However, N application generally increases the emissions of the potent greenhouse gas, N 2 O, from these systems. Nitrous oxide is produced through nitrifi cation and denitrifi cation processes in the soil. Agriculture contributes approximately 67% of the total anthropogenic N 2 O emissions in the USA. Information on how N fertilizer source might affect soil N 2 O emissions from semi-arid, irrigated cropping systems is limited. Halvorson et al. (2008, 2009, 2010a, 2010b) showed N rate, N source, tillage, and crop rotation infl uence N 2 O emissions from semi-arid, irrigated cropping systems in northern Colorado. This article presents a summary of the effects of N source on soil N 2 O emissions from studies conducted from 2009 to 2011 within NT and ST irrigated corn systems located near Fort Collins, Colorado on a Fort Collins clay loam soil. Nitrogen rates were 0 and 202 kg N/ha (0 and 180 lb N/A). Nitrogen sources compared to the commonly used granular urea (46% N) and liquid UAN (32% N) included a controlled-release polymer-coated urea (ESN), stabilized urea and UAN products containing nitrifi cation and urease inhibitors (SuperU and UAN+AgrotainPlus), and UAN containing a slow release N source (Nfusion). A subsurface band ESN treatment (ESNssb) was also included. Each N source, except ESNssb, was surface band applied at corn emergence and watered into the soil the next day with a linear move sprinkler irrigation system. Nitrous oxide fl uxes were measured two to three times per week during the growing seasons using vented static chambers and a gas chromatograph analyzer (see photos). Details on methodology can be found in Halvorson et al. (2011) and Halvorson and Del Grosso (2012).