"Start by creating a compost pile. It's free and as simple as collecting yard waste (leaves, grass clippings, weeds) and food scraps (fruit and vegetable peels, coffee grounds, eggshells) into a 3-by-3-foot pile. Where you are in New Mexico, you may need to water the pile weekly if the weather is hot and dry. The more frequently you turn the pile over, (using a pitch fork) the more rapidly the compost will be ready for the garden. When it's ready, it will be black and crumbly with a fresh, earthy smell. Either till compost into the entire garden or mix it into the soil in each planting hole.
Another inexpensive way to amend soil is with a green manure crop. In the late summer, sow seeds of annual rye, oats, barley, clover, winter wheat, or any number of different choices. (Some home gardeners dispose of leftover garden seed this way, sowing radishes or carrots, for example.) In spring, till the plants into the soil or turn it all over with a garden fork."