CONTROL OF THE NITROGEN STATUS OF LETTUCE BY NITRATE ANALYSIS OF PLANT SAP

D. Alt, A.-M. Füll
In a field trial with lettuce the influence of increasing amounts of nitrogen on yield and on NO3 concentration in the sap of midribs was investigated. The aim of this investigation was to test whether monitoring of N nutrition by sap analysis is possible.
  1. With increasing N supply yield increases were observed; 100 kg N/ha was sufficient.
  2. N fertilization had a strong influence on NO3 concentration in the sap of midribs. In zero-N plants very soon no nitrate was found any longer. In plants receiving N, NO3 concentration first increased and later decreased again. NO3 concentrations in sap rose and remained high longer with increasing amount of N applied.
  3. From the time course of NO3 concentration, a critical value of 2300 mg NO3/1 sap was derived. Below this value N fertilization is recommended.
  4. By means of the NO3 test incipient N deficiency may be detected earlier than by means of visible symptoms. It could therefore be concluded that the NO3 quick-test is in principle suitable for monitoring N nutrition.
Alt, D. and Füll, A.-M. (1988). CONTROL OF THE NITROGEN STATUS OF LETTUCE BY NITRATE ANALYSIS OF PLANT SAP. Acta Hortic. 222, 23-28
DOI: 10.17660/ActaHortic.1988.222.2
https://doi.org/10.17660/ActaHortic.1988.222.2

Acta Horticulturae