Monday, November 13, 2006 - 7:30 AM

Phosphorus and Nitrogen Recommendations for Turf Grown on a Phosphorus Deficient Soil.

Sang-Kook Lee, Kevin Frank, Jeffrey M. Bryan, and James R. Crum. Michigan State University, Crop & Soil Science, Crop & Soil Science, East Lansing, MI 48823, United States of America

Professional turf applicators have reduced or eliminated phosphorus from their fertilization programs based on the assumption that soil phosphorus levels are supplying adequate amounts of phosphorus to the turf. The research will be conducted for three years to investigate the effects of phosphorus fertilization programs on turfgrass performance, and monitor soil and plant tissue nutrient levels to determine the impact of the programs.  The nitrogen treatments were 98, 156, and 208 kg ha-1 yr-1.  The low, medium, and high nitrogen treatments were applied over 2, 4, and 6 applications, respectively.  Nitrogen was applied using a formulation containing 25% of slow and 75% of fast release nitrogen sources that are representative of typical home lawn fertilizers.  The phosphorus treatments were 0, 24, and 49 kg ha-1 yr-1.  Phosphorus was applied using mono-potassium phosphate (0-52-34).  Phosphorus was applied according to the application schedule for the nitrogen treatments.  Potassium was applied from mono-potassium phosphate and also applied to balance K from muriate of potash (0-0-60) to all plots according to soil test recommendations.  During the establishment year, turf color and quality was recorded weekly using a scale of 1 to 9 (1=worst, 6=acceptable, and 9=best). Soil samples were collected monthly and analyzed for nitrogen, phosphorus, and potassium.  Clipping samples were collected every two weeks, dried, weighed and analyzed for nitrogen, phosphorus, and potassium.  In 2004, results indicate that the low N rate treatment had acceptable color and quality ratings without high clipping yields.  The high N rate treatment consistently had the highest color and quality ratings but also had very high clipping yields in comparison to the low and medium N rate treatments.  Overall, there was no effect of phosphorus on color, quality, or clipping weights in 2004 and 2005.