WATER CONSERVATION PRACTICES
The Pajaro Valley is a very rich agricultural growing area with a wide variety of intensive crops. Well water has been the primary source of irrigation water for this valley. As in many areas of California, it has been discovered that the intensive use of well water has depleted the aquifers causing an overdraft situation. This overdrafting of the aquifers has caused seawater intrusion to occur. The Pajaro Valley Water Management Agency (PVWMA) has been looking for ways to bring the aquifer into balance.
One of the ways to bring the water supply into balance is through water conservation practices. In 1999, the board of the PVWMA began a program of offering water conservation grants to growers who wanted to try different irrigation techniques. Growers would have an idea, present it to the Water Conservation Committee and be approved for up to $10,000 of funding. Up to four projects may be funded in a year. Douglas Coty, Water Program Coordinator, believes that "this program facilitates grower experimentation and testing new technology or techniques that they may have been unable to attempt because of lack of funds. Other growers in the Valley also benefit through the opportunity to see what works and what may not in actual field trials."
The growers worked with the infield consultant, Vanessa Bogenholm, for implementation of the new systems and to analyze the results of the new irrigation practices. The new irrigation techniques would be monitored by comparing the new irrigation style with the normal irrigation techniques used by the grower for that crop. Cost of the new irrigation techniques would be compared to previous used irrigation techniques keeping in mind the effect on crop production and water savings.
In 1999, four projects were funded. Project one was the use of a weather station, Soil Moisture Probe from Aquaterr, and an infrared stress monitor called the Scheduler being used to irrigation strawberries. The grower Will Garroutte was very excited to get to try out these new monitoring devices. " I had seen these devices in magazines over the years and always wanted to purchase them to see if I could have a better handle on my water needs for my crop. I was shocked to find out that I was always keeping my soil wetter then was necessary to grow a good crop of strawberries." With these devices Mr. Garroutte was able to achieve a 15% savings on the field of strawberries he used these devices on compared to an adjacent field where the irrigator just used his best judgement. Mr. Garroutte has since purchased more soil moisture probes for his company so all his irrigators use them on a daily basis. According to Garroutte, "the guess work is out of irrigation now." At least 3 more strawberry farms in the valley have purchased the soil moisture probes since this experiment was done.
The second experiment was on using a micro irrigation device known as a spot-spitter to irrigate a potted plant nursery, Rosendale Nursery. The conventional way for Jeff Rosendale to irrigate his potted plants had been over-head sprinklers. In this experiment, problems arose. Labor needs were very intensive because each pot has its own spot-spitter. Rabbits came in and ate the tubing for the spot spritters causing the need for more labor to fix the system. Also he grows many different types of potted plants and he wasn't able to keep the irrigations for the different varieties separate with the spot spitters. "I just feel that in my operation, due to the set up cost and the intensive labor needed, the spot spitters were too expensive as compared to the over-head sprinklers" says Jeff Rosendale.
For the 3rd funded project in 1999, another grower, Suncrest Nursery, recycled the runoff from their overhead sprinklers. The water was collected in a pond, filtered and blended with well water and reused. Suncrest Nursery was able to reduce their groundwater pumping by 26% and are now building the same type of system on another site. Another nursery in the valley has also now built a similar recycling system.
The 4th funded project was with the Dick Peixoto Company comparing drip irrigation and sprinklers on head lettuce. Two different sites were used with half of each field being drip irrigated and the other half being sprinkler irrigated. It was found that yes the drip irrigation could reduce the usage of water, but production could be less also. It was also discovered that drip irrigation is much more labor intensive not just in the design and initial layout of the system, but also in the monitoring of when to irrigate. By knowing the costs associated it was concluded that the system, i.e. tape, header lines, and values, need to be reused for the cost to justify a grower switching from sprinklers to drip irrigation.
For 2000, the PVWMA board refunded the grant conservation projects. Rosemary Imazio a current board member says, " I feel it is important for the agency to sponsor exploring the feasibility of growers saving water. We always need new ideas." Three experiments were funded. The first is a two-year experiment of using tensiometers to monitor the soil moisture at Golden State Bulb Growers. The first year was just to get a feel for the ranges of the readings on the tensiometers. In 2001, the irrigators will actually use the readings to determine when to turn the water on and off, with results being analyzed at the end of 2001.
Another drip versus sprinkler experiment on head lettuce was funded, this time with Steve Dobler of Dobler and Sons, Inc. This time water usage on the drip-irrigated side was 45% less then the sprinkler side. "I wish I had watched the soil moisture a little more closely, I let the drip side get a little too dry some times," says Steve Dobler. Production wise the harvest on both sides of the field was virtually the same for cartons, but the sprinkler side also produced 2 bins of bulk harvested for the shredder. The drip side did not product that large loose head that the processors want. Mr. Dobler was still impressed with the drip irrigation and feels he will become better with it as he does it more. He is now using drip irrigation on other vegetable crops in his operation.
The other funded experiment was a commercial cut rose nursery, DiCicco Nursery, who switched their growing techniques to growing roses in pots with mini-sprinklers as compared to growing the roses in the soil of the greenhouses. These pots were 5-9" deep and planted at a 30% higher density then conventionally grown roses. He also chose a coconut husk medium to grow his roses in which was very water retentive. 30-50% less water was used with this pot growing technique as compared to roses planted in the ground. The roses were also of a superior quality and quantity. All greenhouses when they are replanted at DiCicco Nursery will only be done with this new pot growing technique.
2001 experiments have just begun but Charles McNeish, General Manager of the Pajaro Valley Water Management Agency feels very positive about the water conservation demonstration projects being funded. "We have some very intelligent growers in this valley and they are showing each other what works and what doesn't for their crops. As other growers use these technology it will only help us bring the overdraft situation more inline."
Written by: Vanessa Bogenholm
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