   Garden Soil Preparation - April 4, 2012 Jeff Schalau, Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County Soil preparation is vital to a successful vegetable or annual flower garden. We need to provide sufficient nutrients and organic material prior to planting to ensure production and performance during the subsequent growing season. Adequate tillage coupled with the additions of organic matter and nutrients are the basic components of garden soil preparation. When these materials are combined with proper proportions and placement, your flowers and vegetables will flourish. Organic matter improves overall soil tilth for seedling establishment and root growth. In challenging situations, organic matter will improve water infiltration and drainage of clay soils as well as water and nutrient holding capacity of sandy soils. Soil organic matter breaks down into humus with the help of native soil microbes, worms, and insects. The soil microbes, worms, insects and plant materials also become soil organic matter. Humus is rapidly broken down in our alkaline soils and by the summer heat, so the organic matter pool must be replenished each year. Good sources of organic matter are garden compost, composted manures, green manures (crops specifically grown to be tilled in), and other “non-woody” material. Peat moss is also a source of organic matter, but it is mined from bogs and not truly a sustainable resource. Straw, sawdust, and other “brown” materials are low in nitrogen and should be composted with other “green” wastes or other nitrogen-containing material before being added to the garden. Alfalfa meal, feather meal, blood meal, and cottonseed meal are organic matter sources that also provide nitrogen. Whatever your organic matter source, it can be spread 2-3 inches thick on the soil surface and tilled in to a depth of 10-12 inches. Phosphorus fertilizer can also be added prior to tilling. Phosphorus should be placed where the roots will grow into it. Nitrogen is also a necessary nutrient, but you must consider what the nitrogen content of the organic matter source used as well as the crop being grown. If you are in a limestone area, an addition of soil sulfur will improve soil pH and availability of iron, phosphorus and other nutrients. I use a shovel to till, but a rototiller will make tilling large areas easier. An alternative to spreading organic matter and fertilizers over the entire garden is to prepare soil in beds or rows only. This conserves your organic matter supply by strategically placing it where the plant roots will be. When I plant a row or a bed, I remove the first shovel depth of soil and place it to the side. I place 3 inches of compost, a layer of rich compost (from composted chicken manure), and triple super phosphate (0-45-0) in the hole, then till it in. After this, I rake the soil placed on the side back into the hole and mix again. I don’t use sulfur because my soil is only slightly alkaline (pH 7.5). Once the amending and tilling are done, the entire area should be raked until it is somewhat level. Irrigate to settle the soil and allow it to dry for a day or so. Never work the soil when it is soaking wet as this will cause compaction and/or degrade soil structure. Rake again and plant seeds or young bedding plants. If bedding plants are used, consider “butterflying” the root system at planting time. This is done by splitting the root system partially in half from the bottom and spreading the split portion before planting. Nitrogen can also be side dressed and watered in during the growing season for nitrogen demanding crops such as corn. There are many variations on this theme and other methods are outlined in various vegetable and flower gardening books. In arid regions, annual flowers and vegetable crops always perform best when organic matter is added to the native soil. Nitrogen and phosphorus are also needed to grow vigorous, productive plants. After some experience, gardeners generally adapt these basic recommendations into methods that work for them. For more on vegetable gardening, consult the University of Arizona publication “Ten Steps to a Successful Vegetable Garden”. It is available on-line at: cals.arizona.edu/pubs/garden/az1435.pdf. Follow the Backyard Gardener on Twitter – use the link on the BYG website. If you have other gardening questions, call the Master Gardener help line in the Camp Verde office at 928-554-8999 Ext. 3 or e-mail us at cottonwoodmg@yahoo.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.  |