A Comparison of Automated Thinning with Hand Thinning of Lettuce in California's Salinas Valley: Weed Control and Efficacy.

A Comparison of Automated Thinners with Hand Thinning of Lettuce in the California’s Salinas Valley: Efficacy and Weed Control Elizabeth Mosqueda*1, Richard Smith2, and Anil Shrestha1 1California State University, Fresno, Fresno, Ca., USA, 2University of California Cooperative Extension, Monterey County, Ca., USA *Corresponding author: lillisa5@mail.fresnostate.edu Recent labor shortages in the agriculture industry have impacted growers yield and income, especially in high volume producing areas such as California. Furthermore, it has also created a shortage in supply of crops, especially vegetables, which are a highly labor-intensive commodity. In 2012, lettuce growers in the Salinas Valley, which is California’s largest producer of fresh market lettuce, began to implement the use of automated lettuce thinners to compensate for these labor shortages. These implements were meant to replace the standard lettuce hand thinning crew which goes through the fields to remove closely spaced lettuce plants and weeds. This provides adequate spacing for optimum crop growth. As these implements are relatively new to many growers, assessments on their efficiency to thin lettuce are imperative for grower’s knowledge and livelihoods. Therefore, studies were conducted in the summer of 2014 and 2015 to compare the efficiency of these implements with hand thinning crews. The study was conducted at seven different locations in grower fields in 2014. The experimental design was a randomized complete block with each location being a block. At each location, the field was split into two plots with one side being mechanically thinned and the other side being manually thinned. In 2015, the study was conducted at one location with each treatment replicated four times. In each treatment, six to ten sub-plots were randomly chosen as sampling sites. One to two days prior to thinning, lettuce stand counts and weed counts were taken in each sub-plot. Counts were taken within the crop row. The time taken to thin each treatment plot was recorded. Immediately following the thinning process, lettuce stand and weed counts were taken again in the designated sub-plots. Doubles, or two closely-spaced plants, were also counted for each treatment and measurements were taken to determine the average plant spacing. About 7 to 14 days after the thinning process, a hand crew removed any doubles and weeds in all plots. Again, time taken for this process was recorded. The average lettuce thinning time was 3 to 4 times quicker with the automated than with the manual system. The automated system tended to leave more doubles than the manual system; however, the time required for removal of the doubles was similar between the two systems. Spacing of plants within rows was more accurate with the automated than with the manual system. In terms of weed removal, the automated system was as efficient as the manual system. Therefore, automated thinning holds great potential to aid lettuce growers in the Salinas Valley.