Replacing Conventional Nutrient Inputs for Basal Application with Anaerobically Digested Pig Slurry for Bulb Onion Production

A field study was conducted to evaluate the effect of application rates of anaerobically digested pig slurry (ADPS) on onion growth, bulb yield, and quality during the 2009-2010 growing season. Three levels of swine slurry were used; 50%, 100%, and 150% of the recommended nitrogen (N) rate for basal fertilizer. Bulb dry matter and total soluble solids content decreased with increasing ADPS rates at harvest, while pyruvic acid and total phenol content increased as the rates of ADPS increased. Bulb yield with ADPS of 100% or 150% rates were not significantly different from chemical fertilizer. ADPS at a 150% application rate resulted in a significant increase in N, sulfur (S), and sodium (Na) in bulbs as compared to ADPS having an application rate of 50%. In conclusion, while substituting for chemical fertilizers, ADPS at a rate of 100% based on the N recommendation for basal fertilization can be used to produce quality onions.