Fertilizer Recovery of Cyanobacterial and Commonly-Used Organic Fertilizers and Lettuce Growth Response On Different Soil Textures.

Nitrogen (N) fertilizer plays a crucial role in crop growth and yield development. Lettuce (Lactuca sativa) is a shallow-rooted crop and requires an extensive amount of N fertilizer to produce yield. A greenhouse experiment was conducted for 63 days (early May-mid August 2012) to evaluate the effect of N availability from soil-applied organic fertilizers: liquid cyanobacteria (Lcyb), solid cyanobacteria (Scyb), fish emulsion (Fish), composted manure (Com) and two combinations of soil- and foliar applied fertilizers; [liquid+solid cyanobacteria (FLScyb) and fish emulsion+composted manure (FFCom)] applied at two N rates (56 and 112 kg N ha^-1) on clayey and sandy soils. The treatments were arranged in a Randomized Complete Block Design in a greenhouse at Colorado State University. The fish emulsion treatment recorded significantly higher total leaf area (2189 cm²) compared to other treatments when applied at 112 kg N ha^-1 on clayey soil. Significantly higher yield was also observed at 112 kg N ha^-1 (147 g pot^-1) compared to 56 kg N ha^-1 (117 g pot^-1) in clayey soil. The FFCom treatment recorded the highest root surface area (750 cm² pot^-1) compared to other treatments at 112 kg N ha^-1 on clayey soil. The Lcyb treatment recorded 58 mg N significantly higher total N uptake compared to the Com treatment in clayey soil at 112 kg N ha^-1 while the Scyb treatment recorded 30 mg N higher total N uptake at 56 kg N ha^-1 compared to 112 kg N ha^-1 in clayey soil. The Fish treatment recorded 30% higher fertilizer recovery compared to the Scyb and Lcyb fertilizer treatments at 56 kg N ha^-1 on clayey soil. However, the FLScyb, Lcyb, and Scyb fertilizer treatments recorded 18%, 8%, and 14% higher fertilizer recovery compared to the Com treatment at 56 kg N ha^-1 on clayey soil, respectively. In short, cyanobacterial fertilizer could be a potential N bio-fertilizer for organic farmers in addition to composted manure although it was not as effective as the fish emulsion fertilizer at the rates tested.