UREA AND ANHYDROUS AMMONIA MANAGEMENT FOR CONVENTIONAL TILLAGE CORN PRODUCTION

Nitrogen management for conventional tillage (CT) corn (Zea mays L.) production is highly dependent on local soil and climatic conditions. Nitrogen fertilizer source, time of application, and use of nitrification inhibitors (NI) are components of an N management program which easily can be varied by the producer. An 8-yr study was undertaken in Ohio to assess N fertilizer management for CT corn production on a Crosby silt loam soil (fine, mixed, mesic Aeric Ochraqualf). Nitrogen fertilizer treatments compared in the study were fall and spring-preplant broadcast and incorporated urea, and fall and spring-preplant anhydrous ammonia (AA), with and without the NI, nitrapyrin [2-chloro-6-(trichloromethyl) pyridine]. Each N treatment was applied at rates of 80 and 160 lb/acre. Spring urea also was applied at 240 and 320 lb N/acre. Both grain yield and percent N in the ear leaf at tasseling were increased with increases in N rate for all N source X application time X NI treatments. For increasing rates of N, anhydrous ammonia produced higher yields and gave greater increases in percent ear-leaf N than did urea. Spring-preplant application of both N sources gave higher yields than fall application. Nitrapyrin with spring-applied AA gave no yield or percent ear-leaf N increases. However, NI with fall-applied AA did increase grain yield over fall-applied AA without NI. While significant year-to-year and treatment year variability was present in the study, the 8-yr average results can be used in formulating N management recommendations for CT corn production in similar soils in the North Central USA.