Evaluation of nitrogen sources, starter fertilizers, and amendments for no-till corn production

No-till agricultural production creates a decidedly different soil environment than a conventional system that receives annual tillage, which presents challenges to the management of nitrogen (N) fertility. Two on-farm studies were conducted to evaluate N fertilizer sources, starter fertilizers, and fertilizer amendments on the yield of no-till corn (Zea mays L.). In a two year study involving ten locations, eight N source and amendment combinations were evaluated against each other using a common N rate judged just adequate for optimal yield. Highest yields came from early-applied anhydrous ammonia amended with the nitrification inhibitor, nitrapyrin (which increased yields by 5 bu acre{dollar}sp{lcub}-1{rcub}{dollar}). Surface-applied urea and UAN produced the same average yield, which was 6 bu acre{dollar}sp{lcub}-1{rcub}{dollar} lower than the nonvolatile ammonium nitrate source, and 4 bu lower than unamended anhydrous ammonia. Positive grain yield responses to the urease inhibitor, NBPT, were location specific and highly dependent on climatic conditions conducive to N volatilization. Adding NBPT to urea increased yields by an average of 6 bu acre{dollar}sp{lcub}-1{rcub}{dollar}, but no difference was observed when NBPT was used with UAN. Ammonium sulfate and ammonium nitrate produced similar yields, which were midway between amended anhydrous ammonia and unamended urea and UAN. A second study was conducted at eight locations to determine if early plant growth and yield could be improved by the use of starter fertilizer, and if a nutrient absorption enhancer (polyaspartic acid) could further improve starter fertilizer effectiveness. On average, ammonium-polyphosphate starter fertilizers increased the height (15%) and dry weight (30%) of young plants, and significantly increased the accumulation of shoot N and K at 3, and shoot P at 2 of the 5 locations that were intensively sampled. A statistically significant increase in grain yield from starter fertilizer was observed at 2 of the 8 locations. Adding polyaspartic acid to the starter increased plant height and the nutrient content of young plants by 5%, but did not increase grain yield. These data show that early plant growth can be enhanced from starter fertilizer and polyaspartic acid but many other factors appear to influence whether early growth enhancements ultimately contribute to higher yield.