Pretransplant-N concentration of the nutrient solution influences growth and yield of hydroponic lettuce

Optimum growth and marketable yield of lettuce (Lactuca sativa L.) can be greatly affected by an array of factors including nutrient management during the early transplant plug production period.
The objective of this study was thus to determine the effect of pre-transplant nitrogen (N) nutrient solution concentrations on the subsequent growth and fresh yield of lettuce in a recirculating hydroponic culture.
Seeds of six lettuce cultivars (‘Annapolis’, ‘Buttercrunch’, ‘Dragoon’, ‘Green Forest’, ‘Holon’, and ‘Sparx’) were grown in six pre-transplant N concentrations, four at constant rates (0, 50, 100, and 150 mg L^‑1) and two at increasing rates (0-50-100, and 100-150-200 mg L^‑1) for three weeks during the winter season.
Thereafter, seedlings were transplanted into a recirculating nutrient film technique (NFT) production system inside a greenhouse, where they were grown with a complete optimum nutrient solution containing a constant 200 mg L^‑1 N concentration.
Initial growth of transplants produced with nutrient-less (0 mg L^‑1) solution was noticeably depressed compared with those grown with nutrient-available solutions.
The low seedling vigor of the nutrient-less control did not recover after transplanting into the optimum nutrient solution.
Overall, a significant pre-transplant N concentration×cultivar interaction occurred on marketable yield, shoot dry weight, leaf number and leaf area.
Most notably, maximum fresh yields ranging from 2.5 to 5.8 kg m^‑2 were achieved on transplants grown with a constant 50 mg L^‑1 of N solution for ‘Annapolis’, ‘Dragoon’, ‘Holon’, and ‘Sparx’, while ‘Buttercrunch’ and ‘Green Forest’ recorded maximum subsequent yields of 4.1 and 6.8 kg m^‑2, respectively with a pre-transplant N concentration of 150 mg L^‑1. These results clearly suggest that a pre-transplant nutrient solution of 50 to 150 mg L^‑1 N could be sufficient to ensure optimal transplant growth leading to a maximum crop productivity of lettuce plants in a recirculating hydroponic system during winter.

XXX International Horticultural Congress IHC2018: II International Symposium on Soilless Culture and VIII International Symposium on Seed, Transplant and Stand Establishment of Horticultural Crops

D. Djidonou, D.I. Leskovar

nutrient film technique, transplant quality, pretransplant nutritional conditioning, nutrient solution concentration

https://doi.org/10.17660/ActaHortic.2020.1273.51