Nitrogen Fertilizer Carriers and Their Placement for Minimum Till Corn Under Sprinkler Irrigation

Nitrogen fertilizer efficiency is influenced by source of N and how sources interact with different methods of application. This study was initiated to evaluate various N sources and placement methods for sprinkler irrigated corn (Zea mays L.) grown under minimum tillage on a Sharpsburg silty clay loam (fine, Montmorillonitic, mesic Typic Argiudoll) in 1983 to 1985. In general, no differences were found for the yield parameters measured in this study for any of the N methods or N source combinations at 180 kg N ha⁻¹. At the 90 N kg ha⁻¹ grain yields were equal when N was applied broadcast preplant (using urea-ammonium nitrate, urea, or urea-ureaphosphate as sources) and when anhydrous ammonia was applied (preplant and sidedressed at the eight-leaf stage). Both the broadcast preplant and anhydrous ammonia treatments were found to maximize grain yield at the low N rate. Broadcast preplant and anhydrous ammonia treatments provided superior grain yields, fertilizer N uptake in the grain, fraction of N translocated to the grain, and values for harvest index compared with the banding methods employed (dribble surface and band to the side of the seed) at the low N rate. Marked differences were observed in N utilization efficiency as only the banding methods showed fertilizer response above 90 kg N ha⁻¹ while having no advantages over the other methods at 180 kg ha⁻¹. There were generally small differences among N sources although urea-ureaphosphate did appear to maximize total dry matter yields versus sulfur-coated urea, urea, and urea-ammonium nitrate over the 3-yr period. Measurements made for ear leaf N did not consistently show high positive correlation with grain yield, therefore limiting the use of such a variable for identifying season N deficiencies. This research was supported in part by the Tennessee Valley Authority. Contribution from Nebr. Agric. Exp. Stn., Lincoln, NE as paper No. 8722.