For those of you familiar with intensive gardening or with using mulch, Gardening Without Irrigation by Steve Solomon runs completely counter to everything you know. Nevertheless, it is an excellent introduction to an alternative method with some excellent takeaways, no matter where and how you garden.
For starters, Steve Solomon gardens in the arid regions of the Pacific Northwest. He developed the system outlined in this brief book as a way to minimize irrigation, and discovered in the process that the quality of his produce increased considerably. However, he found that he had to rely on deep-rooted heirloom plants and wide plant spacings to make it work. He also found that a unique schedule of plant feeding was required to ensure growth under dry conditions.
Despite the title, Solomon did not completely eliminate irrigation in his garden. He found that some plants, such as lettuce, still required regular watering. Others required deep watering at specific intervals. (Interestingly, he did find that no water was required for seed germination if special care was taken to properly prepare the seedbed and to soak the seeds prior to planting.)
So what is the secret ingredient that makes using so little water possible? Tremendous root systems that can effectively forage for water deep in the soil. The keys to developing these root systems include:
- Friable soil. Roots cannot penetrate hardpan to find water.
- Heirloom vegetable varieties. Modern varieties are developed with irrigation in mind and often have small root systems.
- No mulch. Mulch holds moisture near the surface of the soil, which in turn encourages shallow root growth.
- Deep watering when necessary. The goal of watering should be to replenish the soil moisture reserve, not simply to provide for immediate plant water requirements.
There are a few consequences to this approach. For one thing, by Solomon’s own admission, it works poorly on very clayey soils prone to cracking, because the cracks permit rapid evaporation of soil moisture. (Of course, improving such soils should be a goal.) For another thing, vegetable roots penetrate deep enough into the soil that the plants no longer have ready access to the nutrients available closer to the surface of the ground, making fertigation and foliar feeding a necessity.
From a historical perspective, the dust mulching technique advocated in this book also presents a concern. The theory behind dust mulching is that cultivation to leave a shallow layer of loose soil on top of the ground breaks up capillary action and therefore prevents the evaporation of soil moisture. While this technique may work well in the Pacific Northwest, a dust mulch is rapidly removed by places with strong winds (e.g., Kansas). In fact, the combination of wind, drought, and dust mulch on a large scale is precisely what led to the Dust Bowl of the 1930s.
But none of this is to suggest that Gardening Without Irrigation is without value. Solomon shows a great deal of understanding of how soil and plants interact with water, particularly in desert regions. And, of course, his results speak for themselves.
The key is to take what fits your specific environment and leave the rest. All gardeners can probably reduce the amount of watering they do if they heed the cues provided by nature in their own location, as Solomon did. For example, if a closer plant spacing were used, as in a tallgrass prairie ecosystem, cultivating to produce a dust mulch would probably cease to be a problem as the plants themselves would protect the loose soil. In far eastern Kansas, one might consider using a mulch of leaves, as would be found in a forest ecosystem, because the average rainfall is higher and will keep the soil moisture reserves replenished.
With these caveats in mind, we can heartily recommend Gardening Without Irrigation as a new way to look at producing nutrient-rich vegetables with less water.