Browsing by Subject "Ammonia Volatilization"

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    Mitigation of Nitrate, Nitrous Oxide, and Ammonia Loss with Time And Source of Nitrogen Application in Corn
    (2022-08) Menegaz, Sonia
    The large need of nitrogen (N) for crop production and the negative impacts of fertilizer on the environment result in a compelling need to identify new or advanced N management practices to reduce N losses while maintaining productivity and profitability. Nitrate (NO3) leaching, nitrous oxide (N2O) denitrification, and ammonia (NH3) volatilization are the most common pathways of N loss when synthetic N fertilizer is applied in agricultural lands. The objectives of this 7-year study (2014-2020) were to evaluate the use of traditional management (urea applied at pre-plant) and advanced [enhanced efficiency fertilizers and split applications] N management practices on i) N losses (NO3, N2O, and NH3); ii) corn yield and profitability; and iii) cropping system N balance including plant N removal and soil N status. The field experiment was conducted at the University of Minnesota Southwest Research and Outreach Center, near Lamberton MN. Four treatments were applied and replicated four times in a randomized complete block design: a pre-plant application of 202 kg N ha-1 of either urea (U) or polymer coated urea (PCU; ESN) (E) and 135 kg N ha-1 as urea with urease inhibitor (Agrotain) sidedressed at development stage V4-6 with 67 kg N ha-1 applied before planting as either urea (U/U+) or ESN (E/U+). Across the 7 years, the advanced management practice E/U+ increased corn grain yield (1 Mg ha-1 or 10%) and total N uptake (TNU, plant + grain N; 18 kg N ha-1) compared to the traditional management practice (U), while E and U/U+ had similar grain yields and TNU to the other treatments. Furthermore, while net economic returns (NER) were not statistically different between treatments, E/U+ generated numerically greater NER per hectare than U ($63), E ($52), and U/U+ ($46). Nitrate-N leaching (measured from 2015 to 2020) was highly influenced by weather. Excess precipitation, especially after fertilizer application, increased NO3-N loads, which was lower for E compared to the other treatments; however, flow-weighted NO3-N concentration was not different between treatments, with only a trend for lower NO3-N concentrations for E. Nitrous oxide emissions (measured from 2018 to 2020) also increased with excess precipitation, especially after fertilizer application. Split application treatments and U did not reduce N2O-N loss, but in wet years N2O-N loss was lower for E compared to the other treatments. This, however, was not observed in drier years or when precipitation was evenly distributed. Unlike NO3-N and N2O-N losses, ammonia volatilization (measured from 2019 to 2020), decreased as the result of excess precipitation that helped incorporate the fertilizer deeper into the soil. Overall, NH3-N loss was lower for E compared to other treatments. Integration of all the variables measured into a N balance calculation showed to be a poor approach to estimate N efficiency or impact on environmental quality because plant N uptake overshadow treatment influence on N loss measurements. Our findings indicate that pre-plant ESN can be considered a strategy to reduce N losses while maintaining crop yield. While split treatments increased corn yield, they did not reduce N losses, which contrasts the common assumption held by many that split applications are better for the environment. Nonetheless, the traditional management practice of pre-plant urea was the least efficient, producing lower crop yields and increasing N losses compared to pre-plant ESN in wet years. This demonstrates that there are N management practices that can improve production and environmental protection and their merit should be explored and refined further.