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Nitrogen cycling and management

by Zixin Lu last modified May 29, 2015 02:03 PM

Current Research Projects

  • Evaluation of Winter Cover Crops to Reduce Nitrate Leaching and Increase Yields in Drip-irrigated Tomato Rotations, PI: Wendy Silk, Martin Burger
  • Testing the memory effect of soils on N2O emissions in rain-fed wheat systems, PI: Chris Van Kessell, Researcher: Steve Fonte
  • Calibrating in-field diagnostic tools to improve the precision of nitrogen management across diverse soil fertility backgrounds, PI: Mark Lundy
  • Remote aerial sensing of reduced irrigation and fertilizer, PI: Darren Drewry (Jet Propulsion Laboratory), S. Ustin, K. Scow
  • Role of Microbiological and Geochemical Heterogeneity in the Fate and Transport of Nitrogen through the Vadose Zone. T. Harter, K. Scow, S. Parikh, R. Schmidt, F. Mukome
  • Effect of agricultural practices on ammonia oxidizer community (Scow, T. Tantayotyai)
  • Compost and organic fertilizers in organic tomatoes (Ecoscraps, K. Scow)
  • Integrated soil fertility management for tomatoes (K. Scow, IAD graduate group)

Research Findings 

Effects of cropping management on nitrous oxide emissions. The nitrous oxide emissions paired with a star were significantly higher among the cropping systems. Graph from Kong, 2007.

The Agricultural Sustainability Institute at UC Davis is partnering with many institutions and researchers over the course of the next two years to complete the California Nitrogen Assessment. The assessment will provide valuable insight for stakeholders into the balance between the benefits of agricultural nitrogen to society, and the effects of surplus nitrogen in the environment.

The impact of nitrogen on the environment has been a key area of research at Russell Ranch (see our list of publications related to nitrogen). In one study at Russell Ranch, the nitrous oxide emissions from the conventional corn-tomato rotation were greater than the emissions from the organic and low-input systems. The study grew cover crop in greenhouses in a 15N atmosphere and then incorporated the cover crop, or 15N-labeled fertilizer, in a microplot in each plot. The conventional system resulted in a greater amount of 15N derived from the fertilizer than the organic and low-input systems and also shorter mean resident times of the fertilizer in one soil fraction. These results indicate that the conventional system may have more rapid N cycling and greater N loss to the environment compared with the organic and low-input systems.

Total denitrification after irrigation or simulated rainfall. The organic system had cover crop and manure incorporated in the spring and had high ammonium content at the April sampling. Both systems were sprinker irrigated in October to simulate rainfall and the conventional system had ammonium nitrate applied five days before sampling. Graph from Burger, 2005.

   Another study at Russell Ranch showed that higher emissions of nitrous oxide occurred when high soil moisture content (above 60% water-filled pore space) coincided with fertilization and high soil nitrogen content. These results suggest irrigation management could control the duration of elevated N2O flux, although inorganic N concentrations should be kept low during the rainy season.

Event Details


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