Management strategies to improve forage accumulation and nutritive value in crabgrass hayfields

Crabgrass (Digitaria spp.) is an annual summer grass capable of self-reseeding and can provide forage with high nutritive value. However, knowledge is still limited about crabgrass management. Our objective was to compare the forage accumulation (FA) and nutritive value of two crabgrass varieties (Mojo and Quick-N-Big) for 2 years under combinations of nitrogen rates and harvesting management. The experimental design was in randomized complete blocks with five treatments and three replications for each crabgrass variety, totalling 15 experimental units for Mojo and 15 for Quick-N-Big, in adjacent fields. Treatments were combinations of nitrogen rates (0, 112, and 224 kg N/ha) and harvest management (harvesting once or twice during the growing season). Nitrogen fertilization increased FA in Mojo and Quick-N-Big. The combination of two harvests and 224 kg N/ha (H2N224) resulted in a total forage accumulation (TFA) of 7840 kg DM/ha/yr for Mojo in 2020 and 8550 kg DM/ha/yr for Quick-N-Big in 2021. The H2N224 management also resulted in the highest crude protein (CP) accumulation. Nitrogen fertilization accelerates plant maturity, which can increase neutral detergent fibre (NDF). In this case, harvesting twice stimulates new tissue production, limits NDF and increases CP and total digestible nutrients (TDN). Therefore, increasing harvesting frequency (twice during the growing season) as N is input increases TFA, CP and TDN, and also enhances N recovery, which may contribute to reducing animal supplementation costs and improve the economic return of forage-based livestock systems.