The development of the processing tomato industry in California’s Central Valley is nothing short of a phenomenal success story that has been built upon numerous innovations and technological advances. Over the past 90 years, CA processing tomato yields per acre have increased over 740% (Fig. 1). California now accounts for over 95% of U.S. processing tomato production [California Tomato Growers Association, 2011; U.S. Department of Agriculture (USDA), 2012b]. While the productive capacity of the Central Valley rests in large measure upon the region’s Mediterranean climate with rain-free summer growing seasons and sustained breeding and genetic improvement efforts (Atherton and Rudich, 1986) that have led to highly adapted varieties, a number of parallel advances in production technology have significantly contributed to this increased productivity.
For example, in the mid-1960s, when the “20-ton per acre yield barrier” was finally broken, the commercial availability of the mechanical harvester coincided with suitable tomato varieties capable of being machine-harvested (Fig. 1). These innovations revolutionized the industry and the proportion of California’s tomato acreage planted to machine-harvested tomatoes rose to over 85% within a few years (Thompson and Blank, 2000). The opening of the California Central Valley Improvement Project in the 1960s brought water through the San Joaquin Valley (SJV) to southern California. This quickly enabled the widespread expansion of surface irrigation of tomatoes throughout the region (California Department of Water Resources, 2012).
By the mid-1980s, when the “30-ton barrier” was broken, another major technology was introduced—drip irrigation for tomato production as a means for improving the uniformity of water application (Table 1; Fig. 1). Initially, drip tape was laid on the surface of planting beds and annually retrieved after harvest. By the mid-1990s, however, tape was increasingly being buried 8 to 12 inches below the soil surface. Water shortages, improvements in drip tape technology, and yield gains with this new, highly efficient irrigation method led to the rapid increase in drip irrigation use (Phene, 2010). By the year 2000, an estimated 25% of the Central Valley’s processing tomato acres were irrigated with buried drip systems and current estimates indicate that these systems account for over 85% of total Central Valley processing tomato acreage. The switch from direct-seeded to transplanted tomatoes also has been a major technology shift during the past decade.
Estimated adoption of drip irrigation in California’s Central Valley processing tomato production from 1980 to 2011. Data based on an unpublished 2012 survey of over 20 University of California Cooperative Extension Farm Advisors, Central Valley tomato farmers, and consultants.
Tomato production systems that have evolved in California’s Central Valley also rely heavily on tillage for seedbed preparation, weed control, and postharvest residue incorporation (Miyao et al., 2008; Stoddard et al., 2007). Intensive tillage and cultivation practices that are used throughout the tomato production season contribute significantly to the crop’s yield potential and help producers manage risks such as seedling pests and the need for uniform plant stands. These tillage and cultivation practices can also be costly (Mitchell et al., 2009; Miyao et al., 2008; Stoddard et al., 2007). Preplant tillage requires not only considerable labor and time but also a number of specialized implements and the corresponding tractor horsepower to pull them. Tillage or soil preparation operations for traditional SJV tomato production systems typically can easily exceed 8 passes (Stoddard et al., 2007) or 10 passes (Miyao et al., 2008) across a field before the crop is planted. While tillage costs historically have not been a major part of overall tomato production budgets (Miyao et al., 2008; Stoddard et al., 2007), because of rising diesel fuel and equipment costs, they are becoming an increasingly important input expense in recent years.
Despite the recent availability of incentives programs such as the USDA, Natural Resources Conservation Service’s Environmental Quality Incentives Program (EQIP) to encourage tillage reduction, as well as the increasing cost of intensive tillage, the majority of SJV tomatoes continue to be produced using traditional, multiple-pass tillage practices largely because these systems are what producers are familiar with and because they have provided reliable productivity in the past (Mitchell et al., 2009; Miyao et al., 2008; University of California, 2012) (Table 2). As a result, tomatoes today are one of the most tillage-intensive annual crops produced in California (Mitchell et al., 2007; University of California, 2012) and ST management systems for SJV tomato production have changed relatively little until quite recently.
Processing tomato acreage in California’s Central Valley under different tillage management systems in 2010. Data based on biennial survey conducted by the University of California’s Conservation Agriculture Systems Initiative (University of California, 2012).
During the past decade, however, experience with a number of tillage system alternatives for tomato production in California has increased (Mitchell et al., In press). A variety of “conservation tillage” approaches that reduce the frequency of tillage in tomato production systems have been evaluated and are now beginning to be used by tomato producers. The term “conservation tillage” as defined by the University of California Conservation Agriculture Systems Initiative (Table 3) refers to management systems, such as no-till (NT) and strip-till, that reduce tillage intensity and soil disturbance to maintain 30% or more of the soil covered by residues from previous crops after seeding, or that reduce the overall number of tillage passes across a field by 40% or more relative to what was conventionally done in 2000 (Mitchell et al., 2009). This latter type of CT systems is termed “minimum tillage.” Because these “minimum till” approaches reduce the total number of tillage operations, diesel fuel usage is also reduced (Upadhyaya et al., 2001). Dust generation reduction of between 60% and 80% has been demonstrated (Baker et al., 2005; Madden et al., 2008). An average fuel saving of 50% and a timesaving of 72% have been reported with one-pass tillage equipment (Incorpramaster; New World Tillage, Modesto, CA) compared with the ST program of disking and landplaning in the Sacramento Valley (Upadhyaya et al., 2001). Additionally, recent investigations using advanced atmospheric light detection and ranging measurement techniques conducted in Los Banos, CA, showed the combined-operations minimum tillage method reduced 2.5-micron particulate matter emissions by 29%, 10-micron particulate matter by 60%, and time and fuel per acre by 40% and 50%, respectively, compared with conventional methods (J. Hatfield, personal communication). For these reasons, these minimum tillage practices can be justified to be a form of CT. These minimum tillage approaches that preserve planting beds are now widely used in conjunction with subsurface drip irrigation tomato production systems throughout the SJV’s West Side region (Mitchell, 2011). However, these alternatives still result in relatively high amounts of soil disturbance and generally do not preserve residues on the soil surface. In this article, we summarize recent research and technological developments related to CT tomato production in California. We start with advances in minimum tillage practices along with farmer innovations in strip-tillage tomato production and then describe recent research findings on NT tomato systems.
Glossary of tillage terminology. To clarify and standardize tillage system nomenclature for California production systems, the Conservation Agriculture Systems Institute has outlined the following general categories of tillage systems. More complete definitions may be found in Mitchell et al. (2009).
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