S06 - Session P2 - Potassium concentration affects leaf expansion and growth of hydroponic lettuce

Authors: Peyton Palsha *, Marc W van Iersel

Crop growth is strongly affected by the amount of light captured by the canopy. This is particularly important in controlled environment agriculture, greenhouses and plant factories, where the electricity costs to provide lighting is high. To increase the amount of light captured by the plants, rapid leaf expansion is crucial. Potassium, I nutrient that is not incorporated into organic compounds, is important for increasing turgor pressure, the driving force for leaf expansion. However, optimal potassium concentrations, and their effects on leaf expansion, have received relatively little research attention. To test the effect of different potassium concentrations on canopy size and growth, lettuce was grown hydroponically with a nutrient solution containing 120 mg∙L-1 N and 100, 150, or 200 mg∙L-1 K+. Plants were imaged twice a week to quantify canopy size. As hypothesized, plant growth was correlated with incident light reaching the canopy, emphasizing the importance of canopy size for crop growth.