Soil Mixing for Ground Improvement

Season

• Amend soil up to four months ahead of the planting date to give it time to "rest." If you're planting in spring, amend the soil in fall, just before the last frost. Remix the rested soil in spring before planting.

Tilling

• Any soil amendment starts with tilling the natural soil. Digging into and mixing natural soil aerates and loosens the foundation for more space and better root growth. Looser soil also makes it easier to add amendments. Dig into the top 10 inches of soil for small vegetable and flowering plants and up to 18 inches of soil for larger shrubs and tree saplings. Always amend a section of soil large enough to hold the entire root ball. Prepare full beds for gardens and individual planting sites for larger shrubs.

Amendments

• Enrich the soil with organic matter to provide long-term acidic nutrition for the plants. Organic amendments hold moisture for plant use and loosen soil for easier root growth. Looser soil leads to quicker, more efficient in-soil drainage as well. The University of Illinois Extension recommends organic compost and rotted manure as valuable amendments. The Oregon State University Extension System goes on to add sawdust, pine chips, straw, peat moss and sand as possible amendments.

Mixing

• Lay the amendments on top of your tilled soil and mix them in to amend the soil. Use 3 to 4 inches of organic matter for small plants (3 to 4 inches of organic matter to 10 inches of natural soil) and up to 9 inches for larger shrubs (9 inches of organic matter to 18 inches of natural soil). Add balanced 12-12-12 or 13-13-13 granular fertilizer for better soil nutrition.