LAMB’S LETTUCE IN DIFFERENT GROWING MEDIA IN CLOSED RECIRCULATING SOILLESS CULTURE (REFEREED)

Nitrate concentrations in lamb’s lettuce often exceed tolerated concentrations when grown in greenhouse soils during autumn and winter due to excessive nitrogen uptake because of uncontrollable nitrogen mineralisation and low light intensity.
The availability of nitrogen is easily controllable in soilless systems when only a small volume of substrate is used.
The aim of the present study was to develop a completely closed, low-cost, reliable soilless system for crops planted at high density by using a low amount of substrate.

In a preliminary factorial trial with a modified plant-plane-technique the influence of (1) different substrates in multipot-plates and (2) withdrawing the nutrient solution at different time intervals was studied.

Lower yields and significant lower nitrate concentrations in lamb’s lettuce resulted from treatments where the nutrient solution was withdrawn prior to harvest.
The water availability in different substrates had a decisive and critical influence on growth particularly during germination.
In further experiments, the frequency of irrigation during different seasons has to be improved.

International Symposium Growing Media and Plant Nutrition in Horticulture

C. Gysi, F. Allmen

Valerianella locusta (L.), organic and mineral substrates, plantplane, soilless system

https://doi.org/10.17660/ActaHortic.1997.450.17