Mode of Managing Nutrient Solution Based on N Use Efficiency for Lettuce ( Lactuca sativa L. ).

In aeroponic cultivation the nutrient solution is an essential component to achieve good production results. And nitrogen is the main constituent element of the nutrient solution and essential element in plant nutrition. Therefore, the management and monitoring nutrient solution and existing nitrogen is fundamental. The experiment shows that three modes of replacing the nutrient solution and three initial pH values and their interaction significantly influenced the fresh weight and dry matter of lettuce. The highest values of fresh and dry weight were recorded in the fifth treatment where there is an interaction between pH 6 and the mode of replacing half of the nutrient solution. The consumption rate of nitrate nitrogen (NO3 -N), ammonium nitrogen (NH4 -N) and gross nitrogen (GN) was higher during stage 1 (10 days after transplanting), especially for the mode of complete replacing nutrient solution.