Influence of Percent NO3−/NH4+ on Growth, N Absorption, and Assimilation by Lima Beans in Solution Culture
1978
McElhannon, William S. | Mills, Harry A.
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.
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