Effect of tillage and anhydrous ammonia application on nitrogen use efficiency of hard red winter wheat

Nitrogen use efficiency (NUE) in cereal grain production is estimated to be 33% throughout the world, and can be lower when N is applied in single, pre-plant applications compared with split N applications. This study was conducted to evaluate tillage system and anhydrous ammonia (AA) application methods on yield, N uptake, and NUE in hard red winter wheat (Triticinn aestivum L.), using a narrow (10 cm) nozzle spacing on a V-blade (Noble or sweep blade) applicator and wide (46 cm) nozzle spacing on a knife applicator. Over the four-year period evaluated, conventional tillage was significantly higher in grain yield in five of eight site years over no-till. However, no-till was significantly higher in grain yield at Lahoma in 2003 where the highest overall grain yield was observed. Mixed results were evaluated in NUE for tillage; four site years of no significant differences between tillage systems and the other four site years split evenly between conventional-till and no-till. The V-blade improved NUE in no-till for three site years at Lahoma, while the knife applicator increased NUE the initial year at Efaw in no-till. Previous crop residue disturbance averaged less than 15% for both AA applicators all four, site years. Mid-season plant populations taken during the 2003 and 2004 crop years were insignificant three of the four site years and plant population did not influence grain yield and NUE. No-till crop production reduced soil compaction at Efaw and the V-blade applicator reduced soil compaction within no-till at both locations. Although the no-till system showed the potential to produce grain yield and grain N levels comparable to conventional tillage, conventional tillage had a distinct advantage in grain yield and grain N uptake over the four-year duration of this study. The V-blade application method improved NUE in no-till at one site, potentially due to reduced soil compaction, but neither AA applicator showed an advantage in conventional tillage. Over the four years of this study no-till reduced soil compaction and conventional tillage produced higher grain yields, but no conclusive advantages w. ere found in NUE for either tillage practice or AA application method.