Many gardeners choose to mulch their potato plants instead of burying them in the ground. This method is just as effective as planting, and the potatoes are cleaner, less susceptible to infestation and the ground doesn't require tilling. However, while hay is an effective mulch for potato plants, straw is a much better choice. Hay and straw are quite similar, and non-farmers often confuse the two. But unlike straw, hay often contains a high number of weed seeds. To avoid a considerable amount of hand weeding down the line, consider using straw to mulch around your potato plants instead of hay.
Clear the planting area. Mulched potato plants do not need tilled ground to grow but it should be free of weeds and other plants (be sure to remove their root systems as well), rocks and other debris.
Check the soil pH. If it is well out of the potato's preferred range of 5.0 to 6.0, amend the soil with lime if it is too acid (well below 5.0), or with sulfur if it is too alkaline (well above 6.0). For soil a little out of range, the additions made in Step 3 will adjust the pH sufficiently.
Spread about 1/4 inch of well-rotted manure or 1/2 to 1 inch of garden compost over the planting area. Alternatively, you can spread 1 to 2 inches of quality all-purpose potting soil over the planting area.
Water the soil with a few inches of water. The planting area should not be bone dry, but there is no need to soak the area. A little moisture goes a long way with mulched plants.
"Plant" your potatoes. Seed potato pieces can simply be placed on top of the soil. Each piece should be 1 foot away from its neighbor in rows that are around 1.5 feet apart.
Apply a 2 foot high layer of hay or straw mulch over the entire planting area.
Give the hay or straw mulch enough water to weigh it down and keep it from blowing away. Then use the back of a rake to press the mulch down and make it more compact.
Replace the hay or straw periodically. Over time, the hay or straw will decay and fertilize the potatoes. As this happens, the mulch level will drop. As the potato plants grow, keep the mulch from getting too thin. The tubers must be well covered or they will develop sunburn. In fact, when potato plants begin vigorously growing, some gardeners choose to cover the hay mulch with a few inches of grass clippings which are smaller and better at keeping out light.