Field and Laboratory Evaluations of N Release From Organic Fertilizers.

Evaluations of organic (those made from waste products) N fertilizers are scant in the turfgrass literature. The objective of this research was to: 1) examine the effect of organic N fertilizers on turfgrass in the field, and, 2) examine N release in a series of laboratory incubation experiments. The work was conducted in 2009 and 2010, with commercial organic fertilizer sources, urea, and an unfertilized control. Hybrid bermudagrass (Cynodon dactylon L. x Cynodon transvaalensis Burtt-Davy) was fertilized at an N rate of 4.9 g N m-2. This same N rate was used in the laboratory, where microlysimeter incubation chambers were used to evaluate N release at 15, 25 and 35 C. All experiments were conducted for 10 weeks. In the field trials, collected data included color and quality, chlorophyll meter readings, soil inorganic and organic N, and shoot density. In both years bermudagrass responded quickly to urea fertilizer, with significantly greener turf within 5 days of application. There was a two week period before bermudagrass fertilized with any organic source was significantly greener than unfertilized control plots. Over ten weeks (both years) there were few long-term differences in inorganic or organic soil N due to fertilizer treatment. Application of any fertilizer source increased shoot density over that measured in the control plots. Over the two year study, bermudagrass fertilized with the soluble N source urea often had better color, and the longevity of that color response was typically equal to that of bermudagrass fertilized with an organic source.