Fall Growth of Cereal Grains in Wisconsin.

Throughout the Southern Great Plains, wheat is managed frequently as a dual-purpose crop, but this production system is not applicable universally; therefore, a wider array of management options can be considered for forage-only uses of cereal grains. Our objectives were to assess the fall-growth potential of wheat (Triticum aestivum L.), triticale (X Triticosecale Wittmack), and oat (Avena sativa L.) cultivars in Wisconsin, and then to further compare the fiber composition and energy densities for these forages. For 2006, yields of DM for all cultivars increased in a quadratic pattern (P ≤ 0.048) over fall harvest dates, reaching a maximum of 3967 kg/ha for Ogle oat. All oat cultivars exhibited stem elongation, but they also displayed a collective 2 to 1 yield advantage over (vegetative) wheat cultivars on the final (30 October) harvest date. Growing conditions were more favorable during 2007, and yields of DM for all cultivars again increased in a quadratic (P ≤ 0.021) pattern across harvest dates. Oat cultivars maintained the identical 2 to 1 yield advantage over wheat cultivars (6275 vs. 3203 kg/ha) that was observed during 2006. Concentrations of NDF increased quadratically (P ≤ 0.012) across harvest dates for all cultivars during both years of the trial; however, these responses occurred primarily between the mid September and early October with limited response thereafter. Estimates of TDN exhibited erratic polynomial responses to harvest date during 2006, and declined linearly (P ≤ 0.038) for grain-type oat cultivars during 2007, but there was no relationship with harvest date for other cultivars (P ≥ 0.072), including forage-type oat. Although TDN was relatively stable across harvest dates, concentrations of truly digestible components comprising the total TDN pool were fluid; generally, reductions of truly digestible CP were offset by increases in truly digestible nonfiber carbohydrate, truly digestible fiber, or both.