Digging For Answers

By Gerald Dobbs

Prior to August 2013, I lived in Michigan’s Lower Peninsula. In my front yard I could dig down four feet or more and hit nothing but rich, loamy soil with an occasional glacial stone thrown into the mix. In addition, I enjoyed having plenty of readily available water. This combination of soil and water has helped Michigan become a powerhouse of fruit and vegetable production in the nation.

A few years later I started working as the Park Services Superintendent at Cordova Recreation and Park District (CRPD) in Rancho Cordova, Calif. Within a month, I read a newspaper article about the soil conditions found in the Sacramento area. It stated that some of the poorest soil conditions can be found in the area of the district’s 36 parks. The state of the soil is a result of the gold mining done in the early- to mid-1800s. The gold miners diverted large quantities of water from the nearby American River to wash away the lighter soil particles with the hope that the heavier gold flakes and particles would be left behind. Much of the topsoil that did exist in the area has been washed away towards the San Francisco Bay area, leaving behind sand, cobble, and some pockets of dense clay soil. Through soil testing, the district discovered a noticeable lack of organic matter and certain plant nutrients in the soil profile as well.

In addition to poor soil quality, my staff members and I faced another problem—a shortage of available water. The primary source of water in Northern California comes from the reservoirs and snow pack in the Sierra Nevada Mountain range on the border of California and Nevada. Typically, the snow pack would melt slowly during the warmer, more seasonal weather and provide more than enough water for Northern California. However, for several years, California has experienced a severe drought to the point that the governor has mandated that each water district initiate a water-reduction strategy for its customers. As one of those customers, CRPD was required to reduce its water-consumption by 32 to 35percent.

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In Search Of A Solution
During that same time a researcher friend of mine flew out to California for a visit. About two years prior to his coming to California, I had hired his son as a field specialist to test the effectiveness of plant-growth regulators on the university campus landscape where I once worked. Little did we realize that when he conducted his work, that part of Michigan would be going through one of the most severe drought conditions it has ever had. Through his efforts, he demonstrated the effectiveness of using plant-growth regulators to:

  • Increase root mass
  • Increase the waxy cuticle layer on the leaves
  • Reduce the number of stomates on the leaves to reduce moisture loss through transpiration
  • Reduce internodal growth on the newer stems.

In other words, the results of his work demonstrated the importance of growth regulators as a tool to help trees and shrubs become more resistant to the effects of drought conditions.

Using this experience, the district began experimenting with the use of growth regulators within a few of the parks. We did notice a distinct difference in the overall quality of plant growth, but felt that there was more to be done. Growth regulators provided a stop-gap solution, but we needed something that was going to be more enduring and beneficial to the landscape plant materials.

Not Holding Water
We decided to look at our soil conditions more closely. After running a few tests in the lawn area at one of the newest parks, Sunridge Park, we discovered that the soil had poor water-holding capacity. For the lawn area to have enough water, it needed to be watered every day. The lawn area would take up as much water as it could during one watering, but the rest of the water would either run-off or percolate down to the water table. Within a day, the soil would dry out in the top layer. When we did probes in this type of soil condition, we found the roots penetrated into the soil about three inches.

After consulting with the researcher, we decided to develop a strategy to improve the overall quality of the lawn area at Sunridge Park. That fall we used our tractor and an aerifying machine to aerate the entire lawn panel in three different directions. Afterwards, we applied a charged carbon product at a start-up rate of 1452 pounds per acre or 33.3 pounds per 1,000 square feet. In the following spring, we applied a liquid humate product to help activate the charged carbon at a rate of 3 ounces per 1,000 square feet. The addition of the charged carbon would help increase the water-holding capacity and the cation exchange capacity of the soil. We hoped to see a dramatic increase in the quality of the turf over the next few months. We did, but there seemed to be something else we needed to do. The lawn area was still heavily infested with noxious weeds, so we decided to incorporate a weed-control program to allow the turf to become successful.

Adding Nutrients
Over the next year we noticed that the quality of the turf did improve, but the vigor was still not evident. We continued with annual aeration of the lawn area, adding charged carbon and liquid humate for two more years. However, it dawned on us that while we were improving the overall quality of the soil by increasing its water-holding capacity, its cation exchange capacity, and air space, the plants needed nutrition. We applied a slow-release of balanced fertilizer with some micronutrients at least two times per year. The lawn area flourished. The color was richer and the turf was much thicker. When using a soil probe, we discovered that some of the charged carbon had migrated into the soil profile by 12 inches and the roots were at that depth as well.

Early in the summer of 2017 the Sacramento area experienced several days of temperatures above 100 degrees. At the same time, we continued to reduce the amount of water being applied to the parks as part of our efforts for water conservation. While Sunridge Park did show some signs of stress from the heat, the lawn area actually maintained its green color, and when the temperatures cooled down, the lawn recovered much more quickly than the lawn areas in other parks that were not treated with the combination of charged carbon and fertilizer nutrition.

Currently, we are treating several more parks, ball fields, and soccer fields with this maintenance regime, and we’re seeing much stronger, healthier stands of turf that use less water and are more resistant to drought conditions.

Gerald S. Dobbs is the Park Services Superintendent for the Cordova Recreation and Park District in Rancho Cordova, Calif. Reach him at gdobbs@crpd.com.