Four Parameter Double Exponential Model Describes Decay of Hybrid Bermudagrass Thatch.

Empirical modeling helps understand decay processes.  Research was done to find a model to describe decay of thatch from hybrid bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon × Cynodon transvaalensis Burtt Davy].  The CO₂-C released from Tifdwarf (TD) and Tifeagle (TE) thatch each 24 h over 20 d was plotted as percent thatch-C remaining (PTCR) vs. time.  Four empirical models were fit to these data to determine which best minimized residual sum of squares.  The model meeting this criterion was the four-parameter double exponential model (FPDEM).  It elucidated two C pools with differing decay rate constants.  Fast-pool C (FP) turnover times (TT) were similar, but slow-pool C (SP) TT differed, with TD decaying faster.  This may have been a function of TE having a higher stolon mass with more lignin and a wider C:N.  When data were corrected for microbial growth efficiency (MGE) SP TT decreased, implying cultural practices increasing MGE enhance decay of thatch.  The FPDEM was successfully used to describe differences in decay of thatch from TD and TE.  Using it in subsequent research may help to expand the understanding of thatch decay.