Week 8: the journey of lettuce

Today, I had a salad for dinner. I discovered that Arizona is the second largest producers in the lettuce industry in the United States and the state’s leading cash crop. 95% of the lettuce produced in Arizona is grown in the lower Colorado River and Gila River Valleys of Yuma County. The production begins with the lettuce seeds. Some seeds are first primed which is a controlled hydration process in which the amount of water the seeds have is controlled by osmoticum, polyethylene glycol. All seeds also undergo pellitizing. During pellitizing, individual seeds are coated with an inert material, usually diatomaceous earth. Priming and pellitizing the lettuce seeds both lead to a shortened shelf life compared to lettuce grown from non-treated seeds. The reason for priming and pellitizing the lettuce seed is that it shortens the germination time and synchronizes germination. Before planting the seeds, the land must be properly prepared. Lettuce grows best in level and well drained fields, so each season fields are laser leveled and deep chiseled. The chiseling breaks up the soil to encourage internal draining and helps to preclude detrimental salt accumulation in the soil. Next, rows are formed and beds are shaped. Finally, the seeds are ready to be planted. This is done with the use of a precision planter, a tractor with rubber belts with small holes spaced to drop a single seed in the precise position. The precision planter is able to plant 6 to 8 pounds per acre, resulting in a total of 20,000 to 26,000 lettuce plants. The plants must be irrigated with 38 to 50 inches of water per acre. The water is delivered via canals from the Colorado River or from the deep wells in Yuma. The plants are threatened by the high Arizona temperatures and are often cooled down with sprinklers that run continuously. Diseases and insects also threaten the production of quality lettuce, so a variety of pesticides and fertilizers are strategically applied to the plants during their growth. The process of germination to harvesting lasts 65 days, for fall harvests, or 120 days, for winter harvests, and the lettuce plants are ready for bulk harvesting. Bulk harvesters have different tasks. Working in groups of three, some harvesters follow wrapping machines, harvesting heads of lettuce not suited for field packaging, and will be used for prepackaged salads. Harvesters place high quality heads in cardboard bins that will be sent to fast food restaurants, but the majority of the harvest will be transported to salad plants. Once all of the heads have been packed, they are transported to a distribution center that also serves as a cooling unit that stores the lettuce at 35 degrees Fahrenheit. When lettuce is stored at this temperature, it increases the shelf life to 16 to 20 days but it is usually distributed within 1 to 2 days. The next stop on the harvested lettuce’s journey is to the salad plant where they undergo a value-added packaging process. They are sorted, washed with a dilute chlorine solution, chopped up for prepackaged and ready-made salads, and sealed in plastic bags. The value-added packaged salad is now ready to make its final journey, to a food store, where I will buy it, bring it home, dress it up and eat it. The end!