21 Impact of Different Maturity Stages on Yield and Quality of Ensiled Johnsongrass (sorghum Halepense (L.) Pers).

Johnsongrass (Sorghum halepense) is a non-native invasive species that is commonly used as hay, but could be ensiled as conserved forage. Therefore, a study was conducted throughout the growing season of 2015 and 2017 to evaluate the yield, fermentation characteristics, and nutritive value of Johnsongrass harvested and ensiled at four maturities: 3 weeks, boot, flower, and dough. The experimental area consisted of sixteen plots divided into four blocks (2.74 m x 4.57 m), and treatment was randomly assigned to plot within block. Plots were harvested at pre-determined maturity and yields, botanical composition, and tiller count were measured. Two cuttings per treatment were utilized for silage production, in which the forage was dried to approximately 55% DM, and packed in mini-silos at a density of 0.24 kg/L. After 10 weeks, the silos were open and silage samples were analyzed for nutrient content and fermentative characteristics. Forage production was highest in 2017 (4701 kg DM/ha) compared to 2015 (3913 kg DM/ha; P < 0.001). Among treatments, Johnsongrass harvested at flower and dough stages produced more than plots harvested at 3 weeks and at boot stage (P<0.0001), but also had the lowest values of TDN (53.74% and 50.91% for flower and dough stages, respectively) and the highest NDF and ADF content (P<0.0001). Neutral detergent fiber corresponded to 52.56% in the 3-week stage, 59.19% in the boot stage, 62.06% for flower, and 65.91% for the dough stage. Acid detergent fiber for 3 weeks and boot stage were 34.81% and 39.19%, while for the flower and dough stages it increased to 40.67% and 42.86%, respectively (P < 0.001). Crude protein was highest for 3-week stage compared to the other treatments (15.41%). The analysis of fermentation characteristics showed a significant effect of treatments on pH values (P<0.0001) of silage, although these differences would not affect the quality of baleage from a practical standpoint. The highest pH value was observed in silage produced from plots harvested at the boot stage (4.52), whereas it was not significantly different among the other three maturity stages. There was no statistical significant effect of treatments on lactic acid: acetic acid ratio (P ≥ 0.2221). These results suggest that johnsongrass can be ensiled as silage successfully, however advanced maturity can negatively impact nutritive value.