Harvest Date and N Application Impact in Bermudagrass Forage Production and Quality.

Hay quality and increase in winter supplementation continues to be two major issues in livestock production across the southern USA.  Supplementation can account for up to 48% of winter feeding expenses.  Although hay production is the primary approach to preserve forages, producers still struggle to practice proper management strategies that can directly impact animal performance and balance nutrient requirements.  The objective of the study was to assess the impact of delaying harvest and N application on forage production and quality.  A ten-year old stand of Sumrall 007 bermudagrass was used for the study during the 2013 and 2014 growing seasons.  The experimental design was a split-plot replicated three times.  Main plots were harvest dates (30, 45 and 60 days).  Subplots were the nitrogen applications (0, 50, 100 and 150 lb N/ac) using Urea-ammonium sulfate (33-0-0S).    Plots were mowed at the beginning of the growing season from five inches down to three inches to have a uniform growth followed by the first N application of 50 lb N/ac for all treatments.  The second N application for the 100 N rate occurred after the first harvest.  The second and third applications for the 150 N rate occurred after the second and third harvest, subsequently.  A 52-inch swatch was taken at a three inches mowing height from the center of each plot using a commercial mower equipped with a bagging system.  Forage subsamples were collected from each plot for dry matter and yield determinations, dried and ground to pass a 2-mm screen.  Samples were analyzed for nutritive value using NIRS using the hay equation for the NIRS Feed and Forage Testing Consortium.  Data was analyzed using PROC GLIMMIX of SAS.  There was a linear increase in total forage yields in 2013.  Total yields in 2014 follow a quadratic response with decrease in yields as N application increased.  This was most likely related to lower precipitation during the 2014 growing season which could have increased nitrogen losses through volatilization.  There was no effect on total yield when comparing harvest dates, with slightly lower yields at the 30-day cutting interval.  On the other hand, there was a significant impact in CP with lower levels at the 60-day harvest and a significant fiber increase, making the 60-day harvest unfit to maintain basic metabolic functions of a dry cow.