Effect of Defoliation Time on Rye Yield and Its Quality under Dual-Purpose Cultivation for Roughage and Concentrate Production

A dual-purpose cultivation system allows cereals to produce both roughage and concentrate during one growing season. To establish a cultivation system for rye, the appropriate time for foliage mowing was determined to ensure a yield of nutrient-rich roughage from the first crop and abundant grain from the second crop. This is because the stage of growth at defoliation affects the yield and quality of both crops. The experimental rye line ‘4R-504’ was grown in two successive cropping seasons; 2019/2020 and 2020/2021. Foliage was mowed at three different growth stages: the booting stage (BT), the early-heading stage (EH), and the fully heading stage (FH). Along with the growth stage, the plants grew taller, and the highest dry matter yield in the first crop was observed in FH (757 g m−2), which was 1.5 times higher than that in BT (480 g m−2). Although the nutritional value was higher in plants harvested at an earlier growth stage, the EH and FH plants showed a higher dry matter yield, resulting in a higher production of metabolizable energy per area. Plants that had been mowed earlier regrew vigorously and produced an abundant amount of grains in the second crop. BT showed the highest grain yield of 239 g m−2, which corresponds to 60% of the yield from the unmowed control. FH produced grains of only 76 g m−2, which barely met the requirement of the dual-purpose cropping system. To enhance the nutritional yield of roughage, it is recommended to harvest the first crop at the early heading stage. Conversely, to achieve a higher grain yield, defoliation should be carried out during the booting stage.