If the per acre value of the crop exceeds the harvest cost, then it pays to harvest. That is, those costs are spent whether you harvest or not. The county extension office has enterprise budgets that will help you estimate your harvest costs for most crops.
Soybeans can make excellent forage and are better suited for late warm-season plantings.
Given the costs of summer annuals, the much reduced yields with late planting, and the weather forecast for continued dry conditions, much more consideration should be given to early planted winter annuals. Cereal rye will give the earliest grazing, followed by oats, wheat, triticale and barley. Cereal rye will also generally produce the largest quantity, followed by wheat, triticale, oats, and barley. Ryegrass should produce tonnage's equal to or slightly greater than the rye and wheat. With good soil moisture winter annuals can be seeded into prepared seedbeds on the first of September in the piedmont and 2 to 3 weeks later on the coastal plains.