Cultivation and Manganese Application Effects On Summer Patch Severity in Compacted and Non-Compacted Kentucky Bluegrass Turf.

Summer patch, caused by Magnaporthe poae, is a common disease of annual bluegrass and Kentucky bluegrass turf areas.  The disease is often most problematic in areas with poor drainage.  Supplemental manganese fertility has been purported to reduce summer patch severity although the effect of this practice on disease is unknown.  A two year field study was initiated on a Kentucky bluegrass (Poa pratensis) turf maintained at 3.8 cm in June 2011 to determine the effects of soil compaction, cultivation and manganese fertilization on the incidence and severity of summer patch.  The study was established as a split plot design arranged in a 2 x 3 x 2 factorial with four blocks.  The main plot factor was compaction, the subplot factors were cultivation and manganese fertilization.  Compaction treatments received 64 or 32 passes with a 1361 kg sheepsfoot roller in 2011 and 2012, respectively to create soil bulk density differences throughout the study.  Cultivation treatments were conducted using a Toro ProCore aerifier with 1.9 cm tines spaced on 2.54 cm centers on 29 June.  Manganese was applied as a manganese sulfate (MnSO₄) solution containing 293 kg ha^-1 on 3 August.  Compacted plots consistently had lower soil water content (5.7 – 7.0%) and higher soil temps compared to non-compacted turf.  Hollow and solid tine aerification reduced soil water content.  Hollow tine aerification increased soil temperatures compared to other cultivation treatments.  Summer patch initiated in late-August, although disease development was not uniform, and no differences were observed at that time.  Results from this study will improve recommendations for cultivation and fertilization to reduce the incidence and severity of summer patch on turfgrass surfaces.