Nitrogen supply, growth and development

Nutrient interruption techniques were used to study the effects of reductions in N supply on patterns of growth and development of lettuce, cauliflower and French bean crops in order to determine the extent to which they interact to influence final yield. The experiments were carried out in a glasshouse using hydroponic techniques to manipulate the N supply at different stages of growth. The results showed that restricting N can affect the rates of growth and development independently, with the latter less sensitive to the availability of N. With lettuce, maturity was delayed slightly as a result of short periods of N deficiency, allowing yields to recover partially from the adverse effects on growth. For cauliflower, a reduction in N supply during curd initiation advanced maturity, but restricting it at other times had little or no effect on rate of development. Maturity date of French beans was not significantly affected by limited availability of N during growth, irrespective of when it occurred. The results demonstrate the importance of manipulating the N supply to optimise effects on both growth and development in order to produce satisfactory yields under reduced input conditions.