Most commonly cereal grains are planted in early fall so they establish root systems needed for optimum growth in the spring. That is why they are good at helping prevent erosion. This also gives the plant sufficient cold days to tiller. Tiller is the process where 1 seed becomes up to 7 stem and seed producing divisions.
Rye will germinate in the spring but without the ability to tiller, less time for root systems to develop and so far fewer seed heads, less root means less erosion control and shorter stems and often smaller seed heads so if you do a spring planting greatly increase your population and fertilize! Rye will grow in sandy soil as long as their is moisture there. It does have a high water uptake during stem and seed production.
Cereal rye matter (when thick from tillering) left on the ground and planted into helps preserve moisture and keep soil temps down. It also helps starve weeds from needed sunlight and encourages soil microbiology needed for healthy plots and plants.