You may choose to add compost at di)erent points for the initial double-dig and when working with a soil with very low amounts of organic matter. Instead of applying compost only after the double-dig, consider spreading a ½-inch layer over the bed before double-digging and/or a ½-inch layer during the dig by incorporating it thoroughly into the 12-inch-deep trench.
Check the soil moisture.The soil should be evenly moist to facilitate digging, but not saturated. If needed, water the area to be dug. For hard, dry clays that have not ever been cultivated, this may mean up to 2 hours with a sprinkler.Begin next steps when soil is evenly moistened. .Check soil moisture and water again if necessary. If your soil has particularly large clods, consider waiting several days and let nature help do the work.
The warm sun, cool nights, wind, and water will help break down the clods. Water the bed lightly every day to aid the process. OPTIONAL (ONE TIME): At this time, sand may be added to a bed with a clayey soil, or clay to a bed with sandy soil, to improve texture. Normally you should add no more than ½ inch (4 cubic feet) of sand or clay.
(More sand may allow water-soluble fertilizers to percolate down too rapidly.) Mix the sand or clay thoroughly into the loosened 12 inches of soil with a spading fork. OPTIONAL (ONE TIME): If the soil is poor (very sandy or very clayey), add on a one-timeonly basis up to a ½-inch lay Loosen the soil an additional 12 inches.
OPTIONAL (ONE TIME): Spread a ½-inch layer of compost on the loosened soil of the first trench. Dig out the upper part of the second trench and move it forward into the first upper trench