Influence of Commercial Organic and Cyanobacterial Fertilizers on Yield and Nitrogen Use Efficiency of Lettuce and Sweet Corn.

Nitrogen (N) fertilizer plays a crucial role in crop growth and yield development of lettuce (Lactuca sativa) and sweet corn (Zea mays). Organic growers often use commercial organic animal-based fertilizers which vary in nutrient composition and have high transportation costs to meet the N demand of crops. Alternatively, cyanobacteria can both photosynthesize and fix N from the atmosphere and can be grown on-site as potential N bio-fertilizer. The aim of this study was to compare the yield, total N in plant tissues, and Nitrogen-use efficiency (NUE) of cyanobacterial bio-fertilizer with commercial organic fertilizers. A field experiment was conducted during the summer of 2013 at the Horticulture Field Research Center, Colorado State University, Fort Collins, CO. The treatments were solid organic fertilizers (feather meal and blood meal) and liquid organic fertilizers (fish emulsion and cyanobacteria) applied at 50 and 100 lbs. of N acre^-1. Liquid fertilizers were applied every two weeks after transplanting while the solid fertilizers were applied prior to planting. There were no significant differences observed in fresh yield, and total leaf N concentration of lettuce. The NUE of lettuce at 50 lbs. N acre^-1 was significantly higher than 100 lbs. N acre^-1. In sweet corn, the fish emulsion (2.1 ton acre^-1) and cyanobacteria (2.4 ton acre^-1) treatments recorded significantly higher fresh yield compared with feather meal and control treatments at 100 lbs. N acre^-1.  No significant difference was observed in leaf or kernel total N concentrations of sweet corn. Fish emulsion and cyanobacteria treatments recorded significantly higher NUE on sweet corn compared with feather meal at 50 lbs. N acre^-1. In conclusion, significant N response was only observed in sweet corn yield at 50 and 100 lbs. N acre^-1. Biweekly application of liquid fertilizers (fish emulsion and liquid cyanobacteria) at 50 lbs. N acre^-1 recorded significantly higher NUE in lettuce and sweet corn compared to single fertilizer application prior to planting.