Commercial table grapes are grown successfully at elevations of 2,000-4,000 feet in the arid regions of the Southwestern US and Mexico. Currently, wine grape production in the Southwest is limited to the high and middle desert elevations (4,000-6,000 ft) of Nevada, New Mexico and Arizona. However, wine grapes have been grown successfully by hobbyists and the University of Nevada Reno at elevations as low as 2,000 ft in communities in southern Nevada with good reports coming from independent laboratories regarding the acid sugar balance required for successful winemaking. Organic grape production is more practical in agriculturally isolated and arid communities because of the lower population of pests.
Commercial grape production using drip irrigation can decrease water use by as much as 1/3 to 1/6 of the amount needed for traditional agricultural crops such as alfalfa hay. Alternative higher value crops such as grapes, if grown successfully and with significantly less water, could improve producer’s economic returns while decreasing water use. Making a value-added commodity, such as organic wine using fewer agricultural inputs, could improve a producer’s overall bottom line.
A major drawback to production of wine grapes at lower elevations in southern Nevada is the possible production losses due to damage by high winds. High winds can reduce fruit set, cause internal tearing of soft plant tissues and decrease the quantity and quality of production. Windbreaks planted to intercept prevailing winds could also decrease crop water use.
A three-row windbreak with an estimated mature plant density of 40-60% was designed to surround Dr. Gehring’s wine grape production area and an existing stand of organic alfalfa. The first phase of the windbreak, Mondale pines, was installed with a drip irrigation system. A weather station and soil moisture sensors were installed to monitor PET and soil moisture for scheduling irrigations and tracking applied water. Applied water will be tracked during the establishment period and eventual crop water use monitored as the vines mature.
The objective of this project is to establish and demonstrate to producers in southern Nevada the principles of using a combination of windbreaks and drip irrigation to decrease water use and minimize plant damage to wine grapes and organic alfalfa. We will:
1) Track the irrigation requirements of the windbreak, wine grapes and alfalfa using a downloadable weather station purchased to track ET.
2) Chart the water applied to the windbreak and wine grapes under drip irrigation and compare it to alfalfa hay under windbreak conditions.
3) Demonstrate the use of a windbreak to decrease crop water use and plant injury and to improve the marketability of these crops.
During the year of planting (2004), there was little native vegetation for rabbits to feed on because of the extreme drought, and so planted trees were heavily browsed causing a significant loss of plants in the windbreak. We replanted the windbreak and installed rabbit guards on all plants. Pines established quickly because of their small size and doubled in less than one year.
We irrigated the windbreak plants by drip irrigation with a precise application rate of one gallon of water per minute. The amount of water applied is determined through knowing the gph of the drip emitters and the length of time the irrigation controller is running per station over time. The valves controlling the bubblers are connected to the irrigation controller and daily-applied irrigation is estimated based upon irrigation controller settings and recorded. Application frequency is changed seasonally to track changes in ET recorded by the weather station.
After changing to drip irrigation for the windbreak, we determined that we needed a 5,000-gallon water tank and booster pump to reduce pumping costs while drip irrigating. Water applied through drip irrigation is confirmed by recording the volume of water used to fill the water tank and dividing this by the number of days between filling it and comparing it to the irrigation schedule.
A weather station was installed at the owner’s expense to compute ET from local weather information for irrigating the windbreak and vineyard. Moisture sensors were installed late in 2005 to monitor soil moisture and fine-tune the ET predictions. Currently, the windbreak is being watered beyond ET during the establishment period to flush salts and encourage rapid establishment. Over time, historical information from the weather station will be used to provide better estimates of ET for developing a grape vineyard in the Amargosa Valley.
It is obvious that this demonstration is being watched closely by local farmers with a great deal of interest. I am confident that this demonstration will open doors for renewed interest in sustainable agricultural practices and perhaps help local farmers transition to higher value crops. This site will serve as a point of reference for other producers in the area for future demonstrations.
BENEFITS OR IMPACTS ON AGRICULTURE
It is too early yet to see much impact from the windbreak plantings as this will happen as the windbreak begins to mature. However, most of the farmers in Amargosa know that windbreaks work but have been reluctant to put them in primarily because they had no method for doing so. This project, along with written information about windbreak design, will encourage people to consider windbreaks for crops that will benefit from them.
There are not yet any adoptions of this type of project in Amargosa Valley. Others have seen how the windbreak goes in and how I am watering it. They are watching it closely, particularly as drip irrigation is not common here and there is a lot of misinformation about its limitations. There are many fears due to the unknown in Amargosa such as rabbit damage to plants and the irrigation system, and they want to be sure it won’t happen to them. This may take a couple of years of watching before they are ready to implement this type of project.
REACTIONS FROM PRODUCERS
Reactions from producers have been positive, most stating that this work is necessary. There are still some questions about whether we are using the right kinds of plants and mostly the drip irrigation as it requires a significant investment up front in a holding tank rather than pumping directly from the well.
RECOMMENDATIONS OR NEW HYPOTHESES
The biggest drawback on this type of system is the initial investment in everything needed for the drip irrigation. Rabbits and how to control them remain the biggest concern among farmers. Plant protectors are needed here regardless of the plants, and that needs to be addressed in recommendations. Even the pines and the grape vines are protected. An added protection is a 36-inch-high mesh fence bent over at the bottom to discourage rabbits from digging under. In addition, each vine is covered with a heavy plastic white vine cover when vines are one year old in addition to the initial mesh vine covers.
Professor Robert Morris drafted a fact sheet on establishing windbreaks and incorporating ideas from other locations where requests for information have been coming. He will put this fact sheet on the University website and make sure it is available through all extension county offices. There has been no media coverage because of our isolated location.