Improving Productivity of Hydroponically Grown Cowpea using Intracanopy Lighting

Abstract

High planting densities of planophile- or horizontal-leafed crops creates a problem called mutual shading, whereby leaves in the upper portions of plant canopies shade lower leaves. This can reduce overall crop productivity. In an effort to negate this problem in growth chambers, light intensity typically is increased from large overhead lamp banks. This is both expensive and inefficient. We have investigated the use of small, low-wattage lamps arranged in three-dimensional space allowing cowpea (Vigna unguiculata L. Walp `IT87D-941-1') to grow up and around the lamps in a technique called “intracanopy lighting.” This illuminates the interior portions of plant stands and keeps the majority of the canopy productive. Results obtained from this novel alternative to high intensity light from overhead lamps showed productivity rates as good as traditional production methods while using less than 25% of the light energy. We have continued to investigate variables associated with improved productivity in high density plantings including: lamp orientation, total light energy, photoperiod, and CO2 concentration. Intracanopy lighting has the potential to significantly reduce the amount of energy required to produce a crop in a controlled environment.