In A Nutshell
They might look the same, but they’re very different products with very different purposes. Hay is a crop that is grown specifically for the purpose of creating hay, while straw is a byproduct of different kinds of crops. Hay is geared toward being a nutrient-rich food for livestock, while straw is more often used for bedding instead of food. Straw also has a wide variety of uses, for everything from a compost pile to an energy source.
The Whole Bushel
Like the old joke suggests, hay is for horses. When farmers plant a hay field, the field is harvested before the grains go to seed. This keeps valuable nutrients in the stalks and makes for a much more well-rounded diet for horses and other forms of livestock. Straw, on the other hand, is a byproduct of other types of grain crops. When crops like wheat, barley, and oats are harvested for their seed, the stalks are left behind. These stalks—which have been drained of most of their nutrients during the process of seed production—are harvested and baled to create straw.
There are different types of hay, and the different types have different nutritional values and usages. Alfalfa, red clover, timothy, bermudagrass and tall fescue are all types of hay grown as feed crops for animals from horses to rabbits. The nutrient value of the hay is also dependent on when it’s harvested—early maturity harvests will contain more of their nutrients than hay that is harvested closer to seed production. For horses, the type of horse and dietary needs will mean a difference in the type, quantity, and quality of hay that is used.
Straw can be made from a variety of grain crops, and regardless of where it comes from, its purposes are generally the same. Some farmers will leave the stalks behind after harvesting seeds, tilling them back into the soil and returning what nutrients are left. Straw is often used as bedding for large animals, but it also has non-farming uses. Straw is a highly valuable renewable energy source, and burning straw can be used to generate power. For example, many power plants in the UK fuel thousands of homes with the burning of straw. A single power plant in East Anglia burns about 210,000 tons of straw in a single year, and that provides enough energy to run about 80,000 homes—a huge number, especially considering straw is highly renewable.
While a hay crop is usually planted with only one end goal in mind—animal feed—straw is much more versatile. A bale of straw can also be used for composting into gardens or in place of dirt. Recent attempts at bringing a bit of home-grown vegetables and country living to the city have yielded some surprising results. A bale of straw can be used as a planting medium for garden vegetables. A wet bale of straw will decay from the inside out, providing a fertile bed for crops from potatoes to herbs.
Straw is often used as insulation for protecting crops that grow through the winter. A surprisingly significant amount of straw produced in the UK is used for the growth of mushrooms and the overwintering protection of carrot crops.
It’s also important to note that some crops—such as sudangrass—can be used as either hay or straw, depending on when they are harvested.
Show Me The Proof
US Forage Export Council: Straw vs. Hay
University of Kentucky: Choosing Hay for Horses
Agriculture & Horticulture Development Board: Straw — what is it good for?
NY Times: Grasping at Straw