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Have you Heard about Hydroponic Lettuce Farming?

Soilless Cultivation Practice

Hydroponic lettuce farming is a soilless cultivation practice that uses water and dissolved nutrient salts to grow plants. Here at Umass Hydroponics romaine lettuce is grown on 4×8 foot tables, where it floats on foam rafts. Lifting the lettuce rafts out of the water reveals a vast web of healthy white roots essential for plant growth. The roots can become over a foot long. Something you would have noticed if you lifted an individual lettuce out of the water a few months ago is something called pythium root rot. Plant diseases are a reality of hydroponic farming, just like any other type of farming. But the kinds of diseases that hydroponic crops get are different from those of more traditional farming practices. For example, powdery mildew particularly effects hydroponic lettuce; this is because the dry foliage and humid greenhouse conditions create the perfect setting for its proliferation. At the Umass Hydroponic facility, we’ve been experimenting with a few organic disease control techniques which seem to be working. The first is the inclusion of a compost tea in the hydroponic water system. This, which has an abundance of microorganisms, acts to displace the microbe population which is causing the pythium root rot, thereby restoring the health of the root microbiome kind of like a probiotic.

The second is the application of a special mix of water, potassium bicarbonate, neem oil, and soap in a sprayer. When applied generously and thoroughly to the leaf surface of the lettuce,  conditions which are hostile to growth are created for the powdery mildew fungus. This is effective because it raises the pH of the leaf surface, while also acting as a potassium supplement for the plant. Otherwise, conditions within a hydroponic greenhouse are much easier to control than, for instance, crops grown in soil.

Easy Nutrient Application & Management

Another positive attribute of hydroponic farming is the ease with which nutrients can be applied and managed. It was actually through hydroponic techniques in the 1860’s that Sachs and Knops showed that simple organic salts were essential plant nutrients (Harris). When dissolved in water, these simple nutrient salts separate into ions like K+ (potassium), P+ (phosphorus), and Ca+ (calcium), which can be easily measured by a device that senses the electrical conductivity of the water flowing through the hydroponic system. Because this is true, nutrient conditions can easily be adjusted to be optimal for whatever crop you are growing. The pH can also be managed in a like fashion. Finally, the amount of light can be easily managed, and to an extent, the humidity and temperature. This is why, it has been suggested by hydroponic professionals, that a hydroponic system is ideal for experimenting with ecological functions like testing relationships between different plants, environments, and microbes because for the most part, variables of the system can be controlled scientifically; and it is, relative to outdoor farming, a closed system.

Oxygen Helps Plant Thrive While Submerged

It may seem strange to some people how plant roots in hydroponic system are totally submerged in water, when it is common knowledge that plants oversaturated with water will drown. In that case, the plants die because of a lack of oxygen ; plant roots perform respiration through their roots, actually obtaining oxygen from pore space in soil. But in hydroponic systems, there is enough oxygen in the water to support the respiration of plant roots. In our system, the addition of oxygen is achieved by a waterfall: water flows off the side of the table and splashes into a tub. The movement and crashing of the water adds to it oxygen, which is then pumped back into the pool where the plant roots are dangling. Hydroponic farming is a fascinating and potentially lucrative way to grow crops. It applies scientific knowledge and technology to create a highly controlled environment optimal for growing. It may seem hightech, but in reality, the process is relatively simple . While requiring some input cost for materials and also space it is feasible for ordinary people to create their own system, learning from text and internet sources.

About Erik Vegeto

Erik is a student of Plant, Soil and Insect Science at Umass Amherst. He has a passion for restorative agriculture and environmental stewardship that drives him forward into new frontiers of thought. Erik loves to read, play guitar, and be creative. One day he hopes to have his own farm and write for a living.

Works cited:

Harris, Dudley. Hydroponics: Gardening without Soil: Easy to Follow
Instructions for the Flat dweller, Hobbyist and Commercial Grower . Purnell, 1971.

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