Prepping Part 2: Improving drainage

Drainage is also very important for good growth. Low lying areas retain more water and often have lower germination (if direct seeding) and higher incidence of seedling diseases. On commercial farms, drainage can be manipulated by adding organic matter and drainage systems (tiles). While tiling a home garden is not often economically feasible or practical you can still adjust the water retention and draining of your soil. An easy way to improve your drainage is by adding organic matter. Organic matter can be a lot of things: kitchen compost, animal manure (usually cow or chicken), grass clippings, spent mushroom compost, or even a green manure (usually a nitrogen-fixing crop, like alfalfa, planted the previous fall). The important thing when using organic matter is that it is decomposed, for most compost piles this means that the material will be dark, earthy smelling and crumbly. 
 

Spring garden plot ready for minor debris removal and waiting for a new shiny layer of compost.

In addition to improving the soil ecosystem, organic matter can also provide important structural changes to your soil. Adding organic matter can increase the speed of water drainage when you have a clay-based soil and can help water retention if you have a sandier soil. When adding compost, apply a 2-3 inch thick layer of compost to the area and work it into the top 10-12 inches of soil. If you don’t have a compost pile, a number of landscaping stores can provide and deliver compost for a moderate fee. In Lansing, Hammond Farms Landscape Supply is one option. In the U.S., compost is often sold by the yard. If you have the measurements of your garden (length and width) then a good landscaper should be able to help you calculate the amount that is needed. If you have a community garden plot structural changes are not recommended and you should limit yourself to improving your soil.

If drainage is still a problem, even after adding compost, there are several structural changes you can implement. Subsurface drainage holes, French drains and raised beds are common structural options. Choosing which option to use depends on your location and the type of drainage you have. If you have compacted soil (thicker than 12-24”) raised beds or subsurface drainage might work the best. French drains are a centuries old technique for draining water. In their most basic form, French drains are shallow trenches with a slight downward slope ending in an outlet. These trenches are filled with gravel. The water seeps into the trench and is slowly carried down along the slope to the outlet. Tutorials for building French drains are available on the web, but be prepared to dig.

Subsurface drainage holes are most suitable when there are thick compacted layers of soil (12-24” thick), and raised beds are not available. They can be made by digging a hole, 3-4 feet deep, using a post hole digger. The hole should be filled with pea gravel (available from landscaping stores) and tamped down. Place drainage holes every 6 feet throughout your garden plot. These deep drainage holes will provide a place for water to seep from your garden plot down to the water table.

 

Standing water is a good indicator that you have a low spot in your beds.

Raised beds are the last structural option I’ll mention. There are a number of reasons to consider raised beds, but from a drainage perspective, raised beds are a great option. In my backyard garden I have a clay-based, heavy soil. In addition, the garden is in a low spot in my yard. The first year I gardened here, I would have to wait weeks for the soil to dry enough to start gardening. By the end of the first year I installed raised beds. They’ve been fantastic. Using raised beds provides better control over the soil composition (soil type and amount of organic matter), and this provides better drainage control. Kits are available at local hardware stores or you can build them using regular lumber. A number of concerns have been raised about treated wood for raised beds, but at least one study actually found that there was almost no movement of the chemicals from some types of treated wood into the soil. However, if you are still concerned you can always use cedar (which will be more expensive) or you can use a heavy 3mil black plastic liner on the inside of your treated wood to prevent contact of your soil with the wood. A traditional width for raised beds is 4 feet wide. This width allows the gardener to reach the middle of the beds without having to walk across anything, reducing the chance for compaction in the future. 

Raised beds can be any height that you wish, this is a nice example of a 3 ft high bed. This is especially convenient for people who might have trouble bending over.

Sources that contributed to Part 2:

http://web.extension.illinois.edu/homecompost/benefits.cfm

http://www.extension.purdue.edu/gardentips/county/countyallen.html

http://www.cmg.colostate.edu/gardennotes/219.html

http://extension.missouri.edu/p/G6985