Most hydroponic systems have inadequate flow rates, which results in reduced
oxygen levels at root surfaces. This stresses roots and can increase the
incidence of disease. Oxygen is soluble only as a micronutrient, yet its uptake
rate is much faster than any other nutrient element.
The nutrient film technique was designed to improve aeration of the nutrient
solution because of the thin film of solution, but the slow flow rates in NFT
cause channeling of the solution and reduced flow to areas with dense roots. The
root surfaces in these areas become anaerobic, which diminishes root
respiration, reduces nutrient uptake, increases N losses via denitrification,
and makes roots susceptible to infection.