Photosynthetic Rate of Lettuce Cultivated on Floating Raft Hydroponic with Controlled Nutrient Solution

Lettuce cultivations in tropical areas are often performed in open field of highlands. Such cultivation practices are often followed by soil erosion. To reduce soil erosion, it is important to shift lettuce cultivation areas to lowlands and to utilize hydroponic system. In such a hydroponic system, photosynthetic rate of the lettuce plants should be evaluated in order to formulate its relation with the cultivation conditions. This study aimed to evaluate the photosynthetic rate of lettuce plants cultivated in floating raft hydroponic system whose nutrient solution was controlled by a newly developed control and monitoring system. Furthermore, this paper presents an ANN model which consists of eight inputs (nutrient temperature, EC, pH, DO, and ORP, air temperature, air humidity, and PPFD) and one output (photosynthetic rate) to describe the relationship between these input parameters and the output parameter. It was noted that the ANN model predicted accurately the photosynthetic rate of lettuce leaves. The ANN model was useful for predicting the photosynthetic rate of lettuce plants cultivated in floating raft hydroponic system on tropical lowland.