Evaluation of Eliminating Fall-Timed Subsoil Tillage In Processing Tomatoes Production

The development of conservation tillage systems for many agronomic crops is a response to both economic (for example, rising price of fuel) and environmental (dust pollution to carbon loss) concerns. For processing tomato production in California, two types of irrigation are practiced; 1) semi-permanent buried drip and 2) furrow. As processing tomato growers in California invest in semi-permanent buried drip irrigation, reduced tillage practices are adopted. To protect the drip tapes buried 10 to 12 inches below the bed surface near the plant line, off-season, broadcast tillage operations such as deep ripping can no longer be practiced. Drip irrigation is more common in the southern San Joaquin Valley. However, the majority of processing tomatoes in California today are produced using furrow irrigation. The conventional tillage practice for furrow irrigation employs fall bed preparation with several high horsepower tractors to pull implements such as stubble disks, subsoil shanks, landplanes, rollers and bed listers. The development of minimum tillage systems is challenged by economic risk, weed issues that traditional soil incorporated herbicides and cultivation have controlled, the need to maintain weed-free and deep furrows for irrigation and the requirement to have a soft bed top to operate mechanical harvesting equipment. We chose to study a reduced fall-timed tillage system that compared a bed cultivator with shallow tillage operation to that of a conventional broadcast tillage. The bed cultivator, Wilcox PerformerŽ, was operated twice, in opposing directions and was preceded by a flail mower following the tomato harvest. The conventional system used 8 passes including a bed lister to create beds to overwinter. Our 2 years of field research at the University of California, Davis campus indicates reduced bed tillage yield outcome was similar to the conventional broadcast fall tillage system. Substantial yield gains were observed in the second year of our monocrop of tomatoes when a single chisel shank in the bed center during the fall was included in the reduced tillage system. Irrigation is by surface furrow.