Which irrigation technique allows for plant trays to float in a constant bed of water?

The technique that allows plant trays to float in a constant bed of water is the floating system, often referred to simply as "float." In this method, trays containing plants are placed on a body of water, effectively allowing the roots to absorb moisture and nutrients directly from the water beneath. This is particularly useful for ensuring that plants receive a consistent supply of water without the need for traditional watering methods, leading to healthier growth and efficient resource use.

The float technique is commonly used in hydroponic systems where water holds nutrients, and controlling the water level is crucial for optimal root health and plant development. This practice not only provides a stable environment for root growth but also helps in minimizing the risk of overwatering or underwatering, which can be detrimental to plant health.

Other options, like ebb and flow, involve periodic flooding and draining of trays but don't keep them continuously floating. Trench culture is another style of gardening that varies significantly from the floating method, focusing on earth beds rather than a water-based system. Nutrient film technology, while also related to hydroponics, relies on a thin film of nutrient solution flowing over roots instead of allowing them to float in a body of water.