Harvest Management Effects On Total and Monthly Yield of Cool-Season Grasses Grown in Pure and Mixed Stands in Tropical Brazil.

Crop-livestock integration has been increasingly adopted in Brazilian production systems, where cropland areas are allocated to livestock during the winter in order to minimize seasonal feed supply in forage-livestock systems. In this scenario, cool season grasses as oats and ryegrass can be interesting options. The objective of this research was to assess how harvest strategies affect productive characteristics such as total mass accumulation (TMA), monthly mass accumulation (MMA) and distribution of monthly production (DMP) of cool-season annual grasses grown in pure or mixed stands, under two harvest strategies, during the winter (May-Aug) in southearstern Brazil. The experimental design was completely randomized with treatments corresponding to the combination of grasses, oats (O) and ryegrass (R) grown as pure stands or oats and ryegrass grown in mixture (OR), harvested either at 95% canopy light interception (LI) or every 30 days of regrowth (DR), in a factorial with three replications. Oats TMA (5.1 Mg DM ha^-1) was lower than that of ryegrass (6.1 Mg DM ha^-1) and of the mixture (5.9 Mg DM ha^-1). Harvesting every 30 d (6.1 Mg DM ha^-1) produced more forage than using LI (5.3 Mg DM ha^-1). Seasonal yield was affected by the “stand type x month” interaction. Oats yielded 15% of the total in May, whereas ryegrass yielded 11% and the mixture 9%. In June oats yielded 26%, ryegrass 19% and mixture 16%. July was the month with the highest accumulation for all the stand types yielding an average of 43% of the total. In August the production declined for all the stand types with all of them producing an average of 25% of the accumulation. The option to for pure stands of ryegrass seems to be the more advantageous, since establishment and management are easier than the intercropping, and the final yield is either higher or similar to that of the mixed stand.