Interseeding Sunn Hemp into Existing Tall Fescue Pasture for Improved Summer Forage Productivity and Nutritive Value.

Incorporating warm-season legumes into tall fescue (TF) pasture can increase productivity and nutritive value when TF becomes dormant and less productive during summer. Our objectives were to evaluate Crotalaria juncea L. (Sunn hemp; SH) as a potential warm-season legume for interseeding into TF using different interseeding methods. A randomized complete block with a split-plot design consisting of four replications of four establishment treatments (Mow-drill: MD, Strip-kill drill: SKD, Pure TF, Pure SH) as main plots, and two nitrogen (N) rates (0 and 50 lbs. acre^-1) as sub-plots was conducted. Measurements consisted of forage yield and nutritive values collected at 45, 55 and 65 days after planting (DAP) during July and August of 2016. Forage DM yield for SKD (3.1 Mg ha^-1) and MD (2.7 Mg ha^-1) were similar but SKD yield was greater than TF (2.5 Mg ha^-1; P=0.0043) and SH (2.0 Mg ha^-1; P<0.0001) at 65 DAP. Crude protein concentrations were similar among SKD, MD and SH (153, 157, 155 g kg^-1, respectively) but were all greater (P<0.05) than TF (135 g kg^-1) at 45 DAP. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were greatest (P<0.05) for TF (600 and 320 g kg^-1, respectively) followed by SKD, MD and SH (503, 494 and 384 g kg^-1 NDF, and 299, 296 and 288 g kg^-1 ADF, respectively). In vitro true digestibility was greatest (P<0.05) for SH (856 g kg^-1) followed by MD and SKD (833 and 824 g kg^-1 respectively) and lowest (P<0.05) for TF (806 g kg^-1) at 45 DAP. Our results suggest that both MD and SKD systems of interseeding SH can be managed in TF pasture for improved DM yield and nutritive value during summer.