If you’re unsure if your soil needs amendments, take note if it dries and cracks in summer, drains slowly, or is difficult to dig—whether wet or dry. Do your rhododendrons and other shrubs wilt in hot weather, even with added water?
Adding organic materials improves the ability of sandy soils to hold nutrients and water. For clay soil, organic additions improve drainage and aeration and help the soil dry out and warm up more quickly in the spring.
Good organic amendments for garden soil include wood by-products, such as sawdust, bark mulch, rotted manure, compost, and grass or wheat straw.
When using organic amendments, make sure they have not been treated with herbicides, as they can carry over into the soil. Inorganic amendments include pumice, perlite, vermiculite and sand.
While manure can be a good source of carbon to add to your soil, it can take years to break down. It is not recommended that you add fresh manure to an existing garden plot. Instead, compost it before adding it in.
To compost manure stock, mix it with a source of nitrogen, such as lawn clippings and vegetable scraps. Turn this mixture into a 3-feet-by-2-inch pile, and try to turn it at least once every two weeks— or when the mixture’s temperature has exceeded and then fallen below 145 F.
Inorganic amendments function primarily as wedges that separate soil particles, increasing soil porosity and aeration.
Sand does not hold water and nutrients well and causes finer silt or clay soils to compact. Mix an organic amendment, such as sawdust, into the soil to improve the sand’s amending properties.
Tilling or discing organic matter into the soil can be beneficial, as it incorporates faster. However, avoid overtilling the soil, as you can create a hard layer of soil that prevents root growth and drainage. One or two passes should allow the organic matter to reach the subsurface level of the soil, giving the microorganisms a chance to begin consuming it.
Another easy way to amend garden
soil is to plant a green manure cover crop—something grown primarily to improve soil fertility by being tilled into the ground while green. Organic matter is added to the soil with the protective benefit of a cover crop.
For example, an optimal winter cover crop for Western Oregon is crimson clover. Plant 12 pounds of seed per 1,000 square feet. Plant no later than Oct. 1, and water the bed so the crop is established before cold weather sets in.
When rototilled or disced under in late April, crimson clover will produce 3 to 4 pounds of nitrogen per 1,000 square feet.
Visit https://tinyurl.com/y48cpemy and https://tinyurl.com/7by2sp5j for more information. Information courtesy of Oregon State University Extension Service.