Corn production with Instinct nitrification inhibitor applied with urea-ammonium nitrate solution and liquid swine manure
C. Lee Burras
Improving N use efficiency of applied N by corn (Zea mays L.), in order to minimize N losses from agricultural fields, is of concern to both producers and environmentalists. Use of nitrification inhibitors is thought to slow the conversion of applied NH4 to NO3, which would reduce N losses from the soil while increasing corn plant N uptake. This thesis includes two, small plot field studies designed to evaluate the effect Instinct (Dow AgroSciences, Indianapolis, IN) nitrification inhibitor had on corn production. The first study evaluated the effect of Instinct spring preplant applied with urea-ammonium nitrate (UAN) solution on corn production, and optimum N rate across six N rates and two application methods. The second study evaluated the effect liquid swine (Sus scrofa) manure (LSM) applied with Instinct at, two rates, and without Instinct had on corn production at two application times in the fall. A comparison was also made in the second study with fall applied anhydrous ammonia (AA) without a nitrification inhibitor.
At low to recommended N rates, early corn growth plant height, mid-vegetative (V10) canopy normalized difference vegetative index (NDVI), stalk lodging potential, and grain yield either had no response, or a negative response, to Instinct applied with spring preplant UAN solution. Above normal precipitation during one year of the study provided an opportunity for Instinct to improve N use efficiency by reducing the economic optimum N rate (EONR) and improving grain yield. Use of Instinct actually increased the EONR by 32 kg N ha-1 across the three year study.
Improved spring inorganic-N and corn grain yield was found when Instinct was fall applied with LSM. Liquid swine manure with the low Instinct rate had significantly higher corn grain yields than LSM with the high Instinct rate and LSM without Instinct, while no difference was found between LSM with the high Instinct rate and LSM without Instinct. Fall applied AA typically had higher NH4-N concentrations within the injected N band, lower NO3-N concentrations in the fall and spring, and higher grain yield than fall applied LSM without Instinct, regardless of application timing. With the inclusion of Instinct with fall applied LSM, grain yields were still not comparable to fall applied AA.
The studies in this thesis show that use of Instinct nitrification inhibitor with applied N does not guarantee a positive corn response. Inclusion of Instinct with spring preplant UAN solution would not be considered a suitable N management practice for improving corn N use efficiency. If LSM is to be applied in the fall, Instinct with fall applied LSM would be a suitable N management practice for improving corn N use efficiency and potentially decreasing environmentally detrimental N losses. However, deciding to apply AA, instead of LSM, in the fall would be a better N management decision.