Influence of Planting Date on Summer Annuals Grass Biomass and Nutritive Value.

Summer annual grasses can produce high biomass yields in a short period of time during the summer months. The objective of the study was to determine the effect of planting dates on biomass production and nutritive value of annual grasses. The study was conducted in the summer of 2019. The experimental design was a split-plot replicated three times. The main plots were the planting dates (PD: Jun 14, July 22, and Aug 19), the sub-plots were the cultivars. Eight cultivars [CUL: conventional and brown mid-rib (BMR)] were established in a prepared seed bed at a rate of 25 lb PLS (Pure Live Seed) per acre. Nitrogen was applied at 50 lb N/ac using urea ammonium sulfate (33-0-0-18S). Plots were harvested and two forage sub-samples were collected for dry matter determination and ensiling. One sample was dried at 130 °F for 72-h and re-weighed for moisture determination. The second set of samples were cut to approximately 2.54 cm (1 inch) in length and left to wilt for 24 h. Approximately one pound of forage was placed in freezer bags, vacuum sealed, and fermented in the dark for 45 d. Samples were dried, ground and analyzed CP, ADF, NDF, and IVTDMD48 using a Foss DS2500 NIR instrument (Foss North America, Eden Prairie, MN) using the haylage equation developed by the NIRS Forage and Feed Testing Consortium (Hillsboro, WI). There were no biomass differences among cultivars. Mean yields were affected by PD (P < 0.001). There was a 65 and 80% yield decrease with the July and August plantings; however, sugar cane may have affected yields for late plantings (July and August). Stand counts were influenced by CUL (P < 0.0001) and PD (P = 0.0150). Nutritive values for CP, ADF, NDF and IVTDMD48 were influenced by CUL and PD.