Nitrogen is the mineral element that plants require in greatest amounts and whose availability often limits growth in agricultural or natural systems. Plants obtain nitrogen predominantly in the form of ammonium or nitrate ions. Although the absorption of ammonium and nitrate from the soil and assimilation of these ions into organic compounds should theoretically be among the most energy-intensive processes in life, no direct measurements of the energy costs associated with these processes have been made. The proposed research would use newly developed plant material and instrumentation to assess these energy costs. The results of this research should improve the energy efficiency of fertilizer applications.
