Audrey Geise

  • PhD Student
My current research is centered around understanding biological nitrogen fixation in California rice. My research aims to quantify biological nitrogen in rice and its contribution to the rice nitrogen budget. In addition, it explores key drivers of nitrogen fixation in rice along with the impacts of common management practices. Enhanced knowledge of the process and its drivers may better allow us to maximize the benefits of fixed nitrogen, reduce nitrogen fertilizer inputs, and improve nitrogen use efficiency and overall sustainability.

Mia Godbey

  • PhD Student
We want to determine the feasibility of growing rice in "no-till"soils with respect to yields, N requirements and weed pressure. Overall, the key dependent variables that will assess affecting grain yield are weed control and nitrogen management. Most rice growers in California till both in the fall and the spring to incorporate rice straw, and prepare the seedbed, respectively. Harvesting equipment can leave deep tracks in the field that prevent rice establishment and promote weed problems, so "no-till" rice systems are often unsuccessful. While fall tillage is necessary to level the field and incorporate straw, minimum-till rice systems with no spring tillage are an option and have been evaluated in the southern United States and Asia. No-till systems have been shown to reduce yields by as much as 5.1%, so our nitrogen trials will help us determine the amount of N fertilizer required to attain the same yields as tilled rice. Foregoing spring tillage can have many benefits such as reduce fuel energy consumption and cost, ability to plant earlier, better control of herbicide-resistant weeds, and minimizing soil disturbance. Having been a member of the University of Maryland's Soil Quality Laboratory studying the effects of early-planted cover crops and nitrogen uptake, as well as agricultural technician at the Beltsville Agricultural Research Center of the USDA, I am excited to work in a completely new crop system to help develop more sustainable and efficient farming techniques.

Zhenglin Zhang

  • PhD Student
I am broadly interested in C:N dynamics and management practices that promote long term soil health for sustained agronomic productivity. My research focuses on nitrogen availability in relationship to rice field management, specifically fallow and continuous flooding. Continuous flooding with winter straw decomposition can cause an accumulation of lignin-derived recalcitrant phenols that bind to mineral nitrogen in the humic faction, making applied nitrogen less available for crop uptake and causing yield losses. The research attempts to understand if increased nitrogen application are needed for continuous flooding to obtain optimal yields and quantify the degree of soil N immobilization caused by soil phenols. Additionally, I am also quantifying greenhouse gas emissions for the two management practices specific to this rice growing region of Sacramento Valley.