November 10, 2012
1 - Raised bed gardeners have several factors that they must consider.
2 - Deer, elk, and rabbit manures may be used in composts and gardens.
Yard and Garden November 10, 2012
I have a couple of questions for you. The first question is about raised bed gardening. I want to garden in the same beds for several years and want to know what I should do to prepare the soil for each subsequent year. The second question is: can you use rabbit, deer or elk droppings to replace cow manure in your compost?
The primary concern with raised bed gardens and containers is the accumulation of mineral salts from irrigation. If the beds are well watered and water leaches through the beds, salt accumulation will be slowed. Irrigation with rain water (when available) will also help delay, or even reduce, salt accumulation. Addition of new well decomposed compost helps renew the soil if salt accumulation is not a problem. If the minerals have accumulated enough to create problems, the soil, or at least a significant proportion of it, should be replaced. Addition of sulfur to the soil will increase the acidity of the soil and the solubility of minerals, the ability to leach salts from the soil. This will help delay salt accumulation. Sulfur will also help plants that need a more acid soil than New Mexico provides. Organic matter (compost) also helps acidify the soil. Be careful when acidifying, it is difficult, but possible, to create a problem by adding too much sulfur.
Building the soil with aggregate materials, coarse sand or perlite, helps the soil to drain and helps with removal of excess salts. The bottom of the raised bed needs to permit surplus water with dissolved minerals to drain away and to avoid problems.
Soil tests each year will help you manage soil salinity with knowledge as well as managing soil nutrients. It is a good idea to test the soil in the raised beds frequently. It is also an important practice to rotate crops so that the same crops are not grown sequentially in the same bed. To grow the same crop in the same bed allows their specific pathogens to build up in the soil until disease problems make gardening difficult or impossible. This also helps distribute nutrient utilization since different crops use different nutrients in different quantities.
If the garden is in an area with high salt soils, and the possibility of subirrigation (moist soil under the bed or standing water in periods of heavy rain) it is possible to create a barrier to the uptake of mineral soils into the soil gardeners create for their raise bed. This is done by placing a layer of coarse rock at the bottom of the bed, a layer of landscape fabric (weed barrier that drains well) above the rocks, then a layer of smaller rocks, more landscape fabric, and finally the "engineered" garden soil. The pore spaces between the rocks below the soil prevents movement of salt upward into the soil through capillary action, yet allows drainage to carry away surplus salts from irrigation water. I learned this technique from the Colorado State University Extension Agent in Grand Junction several years ago. They are in a river valley area which tends to create the problems with salts migrating upward into raised beds.
Regarding the use of rabbit, deer, and elk droppings - they can be used as manure in a compost pile or in a garden. Deer and elk are ruminant animals that chew the cud and doubly digest the material they consume. Their manure is not exactly the same as cow manure, but it is useful organic matter for the garden. This greatly reduces the content of viable weed seeds in their droppings as compared to non-ruminant animals such as horses and rabbits. However, the manure from even these non-ruminants can be used in compost and the garden. Dogs, cats, pigs, and wild carnivore and omnivore manure should not be put into the compost or garden.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!