Post Archives

Energy efficient lighting strategies for vertical or indoor farms

A question many growers are asking is whether vertical farming of hydroponic lettuce production is profitable. Light requirement (daily light integral, DLI) of lettuce can vary from 15-20 mol/m2/day. Lettuce grown under low DLI has slow growth rate (i.e., takes longer to harvest) and appear poor in quality (elongated).  Current estimate is that energy costs for lighting alone can be 40 to 50% of return from sale of lettuce, making it challenging to make profits.  The sustainability of vertical farms will mainly depend on developing research based solutions for decreasing energy costs.  In our lab, we are testing different lighting systems, mostly LEDs, for their efficiencies, energy costs and effect on plant growth.  We are also building biofeedback systems that reduce overall energy (for lighting) consumption in vertical or indoor farms.

Nutrient management for hydroponic lettuce using imaging

Hydroponic lettuce is usually grown by continuously recycling the nutrient solution during production. As nutrients are absorbed by plant roots, stock solution is added to the recycled solution to maintain the electrical conductivity (EC) at a target level.  Because plants absorb nutrients from the solution at different rates, the recycled solutions accumulates elements which are slowly absorbed by the roots overtime.  Therefore, periodic draining of the recycled solution is recommended to avoid negative effects on plant growth and quality.  The research addresses two questions: (i) what is the effect of accumulated fertilizer salts on the plant growth of lettuce and (ii) is there a benefit of adjusting EC of the nutrient solution based on plant growth rate and water use as opposed to maintaining a target EC, and (iii) what is the best way to adjust nutrient solution concentration without impacting plant growth and with minimal environmental impact.  

Hydroponic Lettuce Workshop II at Purdue

Hydroponics Workshop II Greenhouse and Indoor based hydroponics for growing green leaf produce is rapidly growing near urban areas in Indiana. To bridge the gap in learning and increase the competitiveness of Indiana and Midwestern growers, Purdue Extension specialists and researchers in the department of Horticulture and Landscape Architecture have developed workshops that provide experiential learning to growers. Purdue Extension and the department of Horticulture and Landscape Architecture welcomes everyone interested to attend the second hydroponics workshop scheduled for September 8, 2017 at WSLR 116, 170 S. University St., Purdue University, West Lafayette, IN 47907. This workshop focuses on supplemental lighting for winter production, strategies for successful production in indoor or vertical farms, biological pest control, fertilizer recipes and injectors and ongoing research in greenhouses.             Registration is free but required to attend the workshop. Visit or contact Ms. Lori Jolly-Brown at 765-494-1296 for[Read More…]

Our Research Highlights

Click on the link to learn out our research highlights: Phenotyping work update  

Spectral reflectance for measuring crop N status

Nutrient solution concentration for hydroponically grown lettuce in plant factories and greenhouses is adjusted based on electrical conductivity (EC) of the recycled solution. A better approach is to adjust nutrient solution concentration using plant-based measurements.   We are conducting further research to study whether crop reflectance signature can be used to identify nutrient requirements of crops    

Fertilizer requirements of crops using imaging

Lower fertilizer application rates can influence crop quality while higher rates can pose health-risk issues in humans when consumed (ex: spinach and lettuce) and increase plant susceptibility to pests.  Therefore, plants should be supplied with fertilizer in the amounts they need to grow optimally. We are investigating methods to fertilize plants based on the plant nutrient demand.  Our approach is to non-invasively measure crop growth rate using RGB imaging and supply nutrients that match the crop growth rate.  We are currently using this approach for tomato and lettuce.  Using imaging we can estimate crop dry weight on a daily basis.  This can be used to predict the crop growth rates and the amount of nutrients needed by the plant to sustain the current growth.  Below is an example of imaging work done on tomato and relation between image based metric and crop dry weight.  We are developing simple camera and Lysimetry based system that can capture crop growth rate and crop water use. [Read More…]

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