Agronomic comparison of anhydrous ammonia applied with a high speed-low draft opener and conventional knife injection in corn

Citation: Woli, Krishna P., Fabián G. Fernández, John E. Sawyer, Joshua D. Stamper, David B. Mengel, Daniel W. Barker, and Mark H. Hanna. “Agronomic Comparison of Anhydrous Ammonia Applied with a High Speed-Low Draft Opener and Conventional Knife Injection in Corn.” Agronomy Journal 106, no. 3 (2014): 881–92. https://doi.org/10.2134/agronj13.0441.Anhydrous ammonia (AA) is an important N fertilizer in the U.S., and with large farming operations rapid application is needed. This study evaluated the impact of AA application timing and N rates when applied with a high speed low draft (HSLD) or a conventional till knife (CTKI) on corn (Zea Mays L.) production in no-tillage fields. The study was conducted at sites located in Illinois, Iowa, and Kansas from 2007 to 2009. The experimental design was a split-plot factorial arrangement of application method, timing (fall; spring preplant, SP; and sidedress, SD), and five N rates. Fall AA application was least efficient (mean 55 kg N haˉ¹ higher optimum N and 2% lower grain yield, GY), with SP and SD equivalent. The HSLD was comparable to the CTKI with most applications, except when high N rates (180 and 225 kg N haˉ¹) were applied SP. For these treatments AA injury reduced plant population (PP), early season growth, canopy NDVI, and GY. Seedling injury did not occur with any N rate or timing with the CTKI. Shallow AA placement at high speed with the HSLD can provide a viable alternative to traditional deeper knife injection when conditions are suitable for AA application and positioning avoids corn seedling injury. Anhydrous ammonia application with the HSLD, however, should be avoided where high SP AA rates may be placed directly under future corn rows

Corn Era Hybrid Response to Nitrogen Fertilization

Corn (Zea mays L.) N use is of continued interest due to agronomic performance and environmental issues. This 2-yr study evaluated era hybrid response to fertilizer nitrogen (FN) rate in a factorial arrangement of one popular hybrid per five decades (1960–2000 eras) and five N rates (0–224 kg N ha–1). An additional hybrid per era was grown at 168 kg N ha–1. Hybrid productivity and nitrogen use efficiency (NUE) increased across the eras, but not between the 1980 and 1990 eras. Grain yield (GY) increased 65% and total plant biomass 43%, however, total plant nitrogen uptake (PNU) increased only 19% and across N rates was only higher for the 2000 era. At the agronomic optimum nitrogen rate (AONR), there was a linear GY increase of 0.13 Mg ha–1 yr–1 and GY N response of 0.091 Mg ha–1 yr–1, indicating considerable genetic gain. There was no trend in AONR across eras. For plant N status measures, SPAD readings decreased and canopy index values increased across eras. All NUE measures indicated significant improvement in NUE. The apparent nitrogen recovery efficiency (NRE) at N rates near the AONR of each era, however, was not highest for the most recent eras. Harvest index (HI), grain nitrogen harvest index (GNHI), and fraction of total PNU accumulated by R1 were the same among eras. The grain nitrogen concentration (GNC), however, was 24% lower for the 2000 compared to the 1960 era. Corn hybrid development across the 50-yr period improved productivity and NUE, but not the AONR