Most of the winter produce consumed in the United States and Canada is grown in the Yuma, Arizona, region, in Southern California, and in Northern Mexico, and most is processed in Yuma before being shipped out to supermarkets across the country. While the average consumer in the produce aisle of a supermarket may not give a second thought to their lettuce’s provenance, there is actually a highly efficient process for harvesting, shipping, and selling Yuma’s winter crops within a matter of hours.

In this interview, Tom Davis, the general manager of the Yuma County Water Users’ Association (YCWUA), speaks withIrrigation Leader Managing Editor Joshua Dill about the growing, harvesting, and processing of Arizona produce.

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Joshua Dill: Please tell us about your background and how you came to be in your current position.

Tom Davis: I previously managed an irrigation district on the Lower Pecos River in New Mexico. I became general manager of YCWUA 12 years ago. Associations are different than irrigation districts: Associations are private companies, while irrigation districts are quasi-municipalities of state governments. Most of the Bureau of Reclamation’s projects in the West are irrigation districts; there are only a few water users’ associations, although many irrigation districts were originally formed as water users’ associations. YCWUA operates under an operations and maintenance contract with Reclamation and was incorporated with the territory of Arizona in 1903, right after the Reclamation Act was signed into law in 1902.

Joshua Dill: What facilities does YCWUA have, and who are its customers?

Tom Davis: YCWUA operates under contract with Reclamation to divert and deliver Colorado River water from the All-American Canal (AAC) through the project’s canal and delivery system to agricultural lands in the Yuma Valley. It’s a gravity-flow system that was designed and constructed by Reclamation at the turn of the 20th century. The original construction costs were repaid to the federal government decades ago. Our shareholders are the landowners and water right owners that we deliver water to. There are upwards of 1,000 shareholders. Their water rights are attached to their land. The association is just a canal delivery company. We divert water from the AAC, generate and market hydro power, operate and maintain the system, and measure and deliver water to the farmers’ private irrigation ditches. We allocate water on an annual basis to each acre of water right. We assess each acre of water right a tax which makes up most of our operations and maintenance budget. Each acre is allocated 5 acre-feet of water. If that amount is beneficially used, the grower may purchase additional water. Our members have a present perfected water right, which means that beneficial use is the limit and measure of the water right.

Harvesting produce is a labor-intensive process.

What kind of use do those shareholders put the water to?

Tom Davis: We grow crops year-round in the Yuma area. We’re known for our winter crops, which are primarily produce. Most of the lettuce, cauliflower, and broccoli, and some of the seed crops and special crops that are consumed in the United States and Canada during the winter are grown here. Few other places grow the volume of wintertime produce that this area does. During spring and summer, that same produce business moves to the Salinas Valley in California. We also grow desert durum wheat, a fair amount of which is exported to the Mediterranean region to be made into pasta The rest is used here in the United States, primarily for pasta. After produce season, we grow cotton, sorghum, and melons, primarily cantaloupe and watermelon. Those are all grown in the spring months and are generally harvested by mid-June.

Joshua Dill: Is Arizona a big winter crop producer because of its climate?

Tom Davis: Yes, particularly the Yuma area. There are five irrigation districts in addition to YCWUA here in the Yuma area. In other parts of Arizona, there’s irrigated agriculture, but it is mostly summer crops.

Joshua Dill: Would you walk us through the lettuce production process from planting to growing, harvesting, and exporting, especially as it relates to water use?

Tom Davis: We grow every kind of lettuce known. Different kinds of lettuces require different treatments, in terms
of planting and irrigation. Most leafy green varieties are grown on raised beds, although some varieties like baby leaf spinach and arugula, which are referred to as spring mix, are raised on wide beds, which are about 4 feet wide. A salad with individual leaves with weird leaf margins and shapes is what I’m referring to when I say spring mix. They’re planted by seed, sprinkle irrigated over their entire lifetimes, and harvested mechanically. The wide bed varieties are planted in 18 lines per bed with narrow spacing. They are sprinkle irrigated because you can’t reach across the wide bed with furrow irrigation. Moisture doesn’t reach through all the root zones.

We also raise romaine, butter leaf, and iceberg lettuce on raised beds. Lettuce seeds are sprinkle irrigated to ensure that they all germinate on the same day and at the same hour so that they can be harvested the same day to meet shippers’ delivery contracts. Most of the lettuces, except for the wide-bed varieties, are thinned to the optimum spacing at which the plants grow and produce the fastest. Romaine, butter leaf, iceberg, and the other larger plant varieties of lettuce are planted in only two or three lines per bed surface. They are furrow irrigated in the space between the raised beds. Broccoli, cauliflower, and celery are germinated in greenhouses and then transplanted onto raised beds. Broccoli, cauliflower, celery, and some peas and beans are grown in two rows per raised bed. The top of the raised beds for those types of crops are maybe 14 inches wide with the furrow in the middle of each bed. Furrow irrigation is efficient. Heavy shaped rollers are run down the furrows to shape them for optimum water absorption into the root zone under the bed. The water is actually flash irrigated with gravity flow down those furrows, which makes for an efficient delivery of that water.

Joshua Dill: What is the advantage of a raised bed setup?

Tom Davis: The biggest advantage is that it keeps the produce out of the water and away from any floating debris that might be in the water. The water just absorbs sideways into the root zone of the raised bed. The crop itself is not exposed to running water. It’s a taste, presentation, and food safety issue. Wide beds are sprinkled with water, but that water is treated and filtered, so that before it goes into the sprinkler system it is of higher quality than what we divert from the Colorado River.

Joshua Dill: How successful are you in meeting your goal of having all your lettuce ready to ship at the exact same time?

Tom Davis: Weather determines how fast the crop matures. If it’s hotter, it matures faster; if it’s colder, it matures more slowly. Rain also affects the rate of growth. We have pretty consistent weather and little rainfall. The sun shines almost every day. We can know with a fair degree of certainty that our lettuce can be harvested 56 days after planting. We schedule our thinning, weeding, and harvesting well ahead of time, because the germination and growth rate of the produce is pretty predictable.

All produce is labor intensive. Although technology is getting better every year at spacing and weeding, and the wide bed spring mix and baby leaf lettuce is actually harvested with a machine, most of the crops are still harvested by hand. Because all of this needs to be prepared in a short period of time, this area requires hundreds of laborers every day.

Joshua Dill: Would you tell us a little bit about water use efficiency in Arizona in terms of farming a crop like lettuce?

Tom Davis: The efficiency level of furrow irrigation is probably above 80 percent. Water filters well beyond the root zones into the subsurface, and obviously there’s some evaporation, but all in all, furrow irrigation is pretty efficient. Sprinkler irrigation is also efficient. Sprinkler irrigation is also used for both moisture and climate control early in the fall during germination to ensure survival. Produce seeds are expensive. Preparing the land for produce, getting the crop in the ground, and getting the seed germinated costs somewhere in the neighborhood of $6,000 an acre. Raising produce is expensive, but if the markets are right, it’s a good cash crop.

In this area, some produce is raised in Southern California and northern Mexico, particularly in the Mexicali Valley in Baja California, across the Colorado River from the Yuma area. A lot of U.S. growers produce in Mexico. The food safety regulations for farm-to-table crops are strict. U.S. growers struggle both in Mexico and here to meet ever-increasing food safety demands.

All the produce in the regions I mentioned comes into the Yuma area for processing and shipping. During the height of the produce season, a refrigerated truck leaves Yuma every minute, 24 hours a day. The produce has only been out of the field for a matter of hours when it goes into the truck, to the distribution centers, and to your supermarket. A lot of the produce—iceberg, romaine, and curly-leaf lettuce—is not touched between the time it is harvested by hand and when it reaches the customer’s home. That’s why they are called field-to-table crops.

Obviously, food safety becomes more and more restrictive every year. Millions and millions of meals of lettuce are served during the course of the year. Today, if five people get sick with a food-related illness, the whole United States knows about it within hours because of the 24-hour news cycle. The ever-increasing food-safety requirements drive up the expense of growing, producing, harvesting, and processing. There are also the costs of inspection and observation. Human access to the fields is limited when the crop is growing. Growers use different technologies and consultants to evaluate irrigation demands, fertilizer demands, any type of pesticides, and growth changes that happen during the growing season because of changes in the weather patterns. A lot of expertise is involved in growing produce aside from that of the grower. Every carton of produce has a bar code on it that allows it to be traced back to the acre that it was grown on and the day and hour it was harvested.

Joshua Dill: What is your outlook on the future?

Tom Davis: I think food safety regulations are going to become ever more restrictive and expensive. At some point they will reach a point of diminishing returns as their compliance costs cut into profitability. We in the United States like to strive for a risk-free society, which is a good goal but an impossible one. I think you’re going to see more automation in every phase of growing and harvesting as labor gets more expensive and scarce. Right now, the industry uses some automated equipment for thinning, though it just happens to be a crop that’s difficult to harvest mechanically. There is breeding going on to change the physical features of the plant, making them grow higher off the ground so that they are more easily harvestable. A lot of produce is stemless—it grows right on the ground and has to be cut by hand at the ground level. That includes celery, cauliflower, broccoli, and lettuce.

I think you’re going to see a labor crunch and a food safety crunch, requiring more technology in robotics. The food processing plants operate nearly 24/7. They typically shut down 1 hour every 24 hours and totally break down all the equipment and sterilize it. I think we will see the development of a kill step prior to shipping which will kill any bacteria that may be on the produce. You can’t raise something in an open environment or even in a greenhouse and have it be absolutely bacteria free. Those little vermin are in all the machines, on people’s hands, and in the air and soil. We need to develop a kill step that is economical and doesn’t destroy the nutritional benefits of the produce but does destroy dangerous bacteria. There is a tremendous amount of research going into that; I think we’ll see it implemented in a few years.

I don’t see much of this produce being grown in other countries and imported, like some crops are. One reason is the food safety requirements. The other is that produce has a short lifespan and has to be constantly refrigerated. It doesn’t do well in long shipping processes. Here, it’s cut in the fields, processed, put on a truck, and delivered to supermarkets in a matter of hours. What you see stocked in the supermarkets rotates out of there really quickly.

I think you’ll see produce continue to be a part of the American diet. We’ll have to deal with these growing and harvesting complications with increasing technology, which increases costs. Plant breeders are constantly striving to modify the genetics of their crops to increase their nutritional value, hardiness, and yields. We have a middle class in this country for three primary reasons: We have cheap water, cheap food, and cheap power. If the cost of any of those three factors greatly increases, it starts reducing disposable income. There is constant concern about things that add costs to production, processing, and shipping and handling. Every step of the process must be profitable or it will not take place. The end product must also be safe and affordable for the consumer. We have to ensure that we can provide constant, stable, healthy, and nutritious food supply at an affordable price.

Tom Davis is the general manager of the Yuma County Water Users’ Association. He can be contacted at or at (928) 581-1882. For more about the Yuma County Water Users’ Association, visit