Dry Farming

By Tami Reese, UC Master Gardener

The dry farm plot in the Demonstration Garden was started in fall of 2014.  The purpose of the plot was to grow vegetables without additional summer irrigation.  Our experience revealed several factors key to a successful dry farming plot:  adequate planting bed preparation, a well-planned watering schedule and careful plant selection.  The following guidelines are derived from our experience in the Demonstration Garden.

Choosing a Site:

1. The ideal site would be level and have native clay soil. Clay soil has greater water holding capacity then sandy soil and would not require additional amendments.
2. The Demonstration Garden dry farm plot is approximately 10 by 20 feet. The size and shape of the plot should provide sufficient space for tending and harvesting without excessive walking within the plot to avoid soil compaction.

Preparing the Bed:

1. Prepare the bed in early spring. If a handful of clay soil crumbles easily, the bed is ready to be worked.  
2. Till the entire bed to a depth of at least 24 inches. Avoid walking on the bed after it has been tilled.
3. Choose your planting locations and mark each by digging a planting hole. Leave 3 to 4 feet between each to allow ample room for root growth and limit competition for water and other resources.
4. Prepare each planting hole by digging down 4 feet and then filling it up with a mixture of 40% of the removed native soil and 60% compost.
5. If the planting bed is on a slope, build up the front of each hole to help with water retention.
6. Once all the holes have been dug and filled, cover the entire bed with 6 inches of mulch. The deeper the mulch the better.  In our plot, we used straw as it was readily available.
7. After the first year, the only maintenance needed is re-digging the planting holes. The mulch layer does not need to be removed.  New mulch can be added to maintain a minimum of 6 inches.

Watering the bed:

1. Choose the plants and the approximate planting date. Consider your location’s planting zone and last frost date.  San Luis Obispo is planting zone 8A.
2. Count backwards 8 weeks from your planned planting date to determine the start of the watering schedule. For example, if the planting date is the second week of May, the watering schedule will start the second week of March.
3. Pick which day you’ll water and plan to water the same day every week. Water each planting hole for 10 minutes each week.  This may require watering, letting it drain, and repeating several times to achieve 10 minutes for each planting hole.
4. After watering, always cover the planting holes with the mulch.
5. Maintain this weekly watering schedule for 8 weeks. In the event of rain, the amount of precipitation and thickness of the mulch will determine how much additional irrigation is needed, if any.
6. After 8 weeks of watering, do not water for the remainder of the year.
7. Ignore the temptation to water; just repeat the words, “dry farming, dry farming”. If the bed has been prepared as described, the roots will spread widely and deeply enough to find water.

Plants:

1. Plants can be started from seed indoors and planted as transplants. This option allows for a greater variety of low water use plant choices.  Our current choice for the Demonstration Garden plot is to purchase transplants locally.
2. Plants successful in our plot include tomatoes, watermelon, winter squash and spaghetti squash.
3. Tomatoes should be left to their natural sprawl growth habit. Do not grow in cages or stake.  The sprawling growth habit will help retain soil moisture.
4. With the dry farming method, potato leaf varieties of tomatoes are more successful than regular tomato leaf plants. Husky cherry and Roma tomatoes produced well in our garden.
5. Suitable watermelon varieties include the small icebox varieties such as Moon and Stars.
6. Pumpkins and cantaloupes are also suitable options for dry farming.