Influence of Percent NO3−/NH4+ on Growth, N Absorption, and Assimilation by Lima Beans in Solution Culture1
- William S. McElhannon and
- Harry A. Mills2
Application of the appropriate quantity and form of N in proportion to the rate of plant uptake and assimilation could significantly increase the utilization of applied N fertilizers. The objective of this study was to determine the influence of various percentages of NO3− to NH4+ and N concentration on N absorption, assimilation, growth, and yield for lima beans (Phaseolus lunatus L.) when grown in solution culture. Nitrogen was supplied as Ca(NO3)2 and/or (NH4)2SO4 at three N concentrations and five percentages of NO3− to NH4+. Peak absorption periods for NO3− and NH4+ were observed when NH4+ supplied 50% of the N. Two peak absorption periods for NO3− occurred, the first at the initiation of inflorescence and the second during pod filling. Peak periods of NH4+ absorption occurred during initiation of the inflorescence, pod development, and pod filling.
Dry weights of all plant parts were consistently higher when NO3− was 75% or more of the N. Lima bean root morphology was altered at all N concentrations when NH4+ was more than 50% of the N. Plant N content was highly influenced by the form and level of N available for assimilation and may not be an accurate indicator of the N available for pod development.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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