The limpness of the plants is not a symptom of hydroponic production but rather a symptom of poor crop management.
Role of Nutrition #
The turgidity of the plant is heavily impacted as a result of the nutrition provided. In conventional hydroponics, operators focus heavily on the essential macro and micronutrients. As a result, many producers do not recognize the importance of beneficial nutrients and other trace elements, primarily in regard to the limpness of the plant; the 3 nutrients that play the biggest roles are Silicon, Boron, and Calcium; these nutrients have a synergistic effect in the development of the cell walls and tissue.
Silicon is often one of the main missing nutrients that are forgotten in hydroponics and aquaponics. Often this is forgotten because of a misunderstanding of plant uptake of Si. In books, we are taught that some plants are heavy accumulators of Si, moderate accumulators, or non-accumulators. Lettuce is seen as a non-accumulator, but this term is misleading. By definition, a non-accumulator does not actively take up the nutrient, but passively it will absorb the nutrient; thus, hydroponic and aquaponic producers have seen this as an unnecessary nutrient, but it is essential in creating healthy, pest and disease suppressive plants.
Trace Elements #
Outside of silicon, many trace elements are required to build metalloproteins, which help build the plant’s structure and secondary defenses. Many of these same metalloproteins are needed for animal health and a complete set of building blocks to use for the organism’s development. In humans, when some of these are absent from the diet, we see increased cases of Irritable Bowel Syndrome (IBS), leaky gut syndrome, and immune issues. Hydroponics is not alone in being absent from these. Often conventionally, soil-grown crops do not have a biologically active environment that will allow for various trace elements’ uptake. In addition to this, when soil crops are sprayed with certain pesticides, this can also disrupt the building of these various amino acids and proteins in the plants, which increases those same diseases among humans and livestock.
The other factors that can affect limpness are the temperature and time of day at harvest and the temperature the product is stored at. For the best quality, leafy greens should be harvested before the sun rises because the plants’ stomata will be closed and prevent transpiration post-harvest. A healthy lettuce crop should be able to maintain its crispness 3-6 weeks after harvest without issues.
Learn More #
Want to learn more? Check out this talk Joe Pate gave on plant nutrition.