GROWING TOMATOES WITH LESS TILLAGE Jeff Mitchell University of California, Davis Since 1999, we have evaluated conservation tillage (CT) and cropping (CC) practices for tomato production in an 8 acre field in Five Points, CA. The objective of this work have been to compare standard till (ST) with and without (NO) winter crops and conservation tillage with and without crops in terms of economics, productivity, soil properties and dust emissions through a tomato cotton rotation. The study field is divided in half to allow both crops to be grown in each year. A summary of the first five years of this work is presented here. Tillage management The standard tillage systems have been managed as is customarily done in the West Side San Joaquin Valley region. Beds are disked and reformed following harvest of each crop. Prior to tomatoes, the beds are also shaped with a power incorporator. The standard till crop system uses a triticale/rye/vetch green manure approach with the crop disked in each spring before establishing the summer crops. The CT systems use about 50% of the overall tillage, or soil disturbance operations as the ST systems. Tomatoes are no-till transplanted and cotton is no-till seeded into beds that haven t been worked or moved since the beginning of the study, - except for a shallow cotton root undercutting following harvest for Pink Bollworm management compliance. Tomato beds have been quite rough following the one-pass fall cotton stalk management operation and are rereadied using furrow sweeps at the time of transplanting and during in-season cultivations. In the CT crop systems, Chopping triticale/rye/vetch crop using Buffalo Rolling Stalk Chopper in Five Points, CA conservation tillage study, 2005. Transplanting processing tomatoes into crop and cotton residue (left) and cotton residue (right) in Five Points, CA conservation tillage study, 2004.
the crop is sprayed with glyphosate, chopped and left on the soil surface as a mulch before transplanting tomatoes or planting cotton. A summary of pre-tomato tillage operations used in each system is shown in Table 1. Table 1. Tillage operations used in standard and conservation tillage tomato systems, Five Points, CA 1999 2005 Standard tillage Conservation tillage undercut cotton undercut cotton disk transplant tomatoes disk rip disk list beds pwer incorporate beds transplant tomatoes CT equipment A few equipment modifications have been made in the CT system. A three-row transplanter sled fitted with 20 diameter coulters ahead of each transplanter shoe, residue-slicing disks in front of each sled, and additional press wheels behind the transplanter drive wheels to seal seedlings into the soil, was used. A Sukup high residue corn cultivator (Sheffield, IA) was converted to a 3 row 60 configuration and bed-top L-sweep blades were added for tomato bed cultivation. Sidedress fertilizer Cultivating processing tomatoes in conservation tillage (high residue) study in Five Points, CA 2004 was applied using Yetter Mfg. (Colchester, IL) high residue liquid or dry fertilizer applicators that had coulters fitted in front of the shanks. Tomato transplanter fitted with coulters ahead of transplanter shoes, residue manager disks ahead of sleds, ridging wings behind sleds in furrows and supplemental closing wheels behind transplanter shoes, Five Points, CA 2005 Applying liquid fertilizer as sidedress to fresh market tomatoes in conservation tillage study, Parlier, CA 2002 Yields Processing tomato yields (cv Heinz 8892 ) are shown in Table 2 for 2000-2004. Letters following each yield number indicate whether there were statistically
significant differences between treatments within a given year; if the letters in a particular column are different, this indicates that the systems likely had significant yield differences. CTNO yields matched or exceeded those of either ST systems in all five years of this work while using considerably less tillage. Yields of the CTCC system were lower than the other systems in 2000 and were lower than the CTNO in each of the next two years of the project as well. We observed that tomato plants often grow more slowly early in the season over the heavy CT crop mulches and this is perhaps due to lower above and below mulch temperatures that we have measured. We also observed more surface trash entering the harvester in the CT systems, however, virtually all of this was typically removed by the harvester s suction cleaning mechanism before entering transport trailers. Table 2. Tomato yields 2000 2004 (tons/acre) in field comparison of standard and conservation tillage production in Five Points, CA Std till no Std till crop Con till no Con till crop 2000 2001 2002 2003 2004 58 a 61 b 46 b 42 c 46 bc 53 b 63 a 43 b 45 b 42 c 56 a 64 a 56 a 54 a 52 a 51 b 61 b 43 b 52 a 48 ab These results indicate at least the shortterm potential to produce tomatoes following cotton with considerably less tillage than is currently done in most production fields. The tillage management approach that has been pursued in this study seeks to reduce primary, intercrop tillage and depends on subsequent, early-season bed reconditioning with the transplanter and cultivator operations. By doing this, beds have been left quite rough during the winter and into the spring and this may be a management strategy that today s growers may not be comfortable with because earlyseason beds are rather degraded and may not be well shaped. In this study, however, we Transplanting tomatoes into unworked cotton beds from previous season in conservation tillage study, Five Points, CA 2005 have found that it is possible to establish tomato transplants into these beds, to rebuild beds using the transplanter and cultivator that are both fitted with ridging wings, or furrowing tools and to successfully harvest fruit with this management system. With this approach, early cultivation is needed to recreate furrows and to clean residues out of furrows to enable surface irrigation. Within this CT tomato system, the largest challenge has been to consistently manage weeds during the entire production season. The strategy we have pursued involves cultivation, - generally two to three times per season, - and hand weeding. However, because herbicides have not been incorporated into the soil, the CT systems have consistently had many late-season weeds grow in the furrow and they have not been effectively managed because the tomato plants are by then too big to allow
herbicide spraying or cultivation. There is thus a need to improve the CT systems, particularly late in the season. incorporate herbicide in the transplant line. Cultivation has not been used in either of these commercial fields. In one case, subsurface drip irrigation is carefully managed to avoid wetting the soil surface, thereby controlling weeds to a great extent. Cultivated processing tomatoes in conservation tillage study, Davis, CA 2004 CT production at San Joaquin Valley tomato farms Two commercial variations of the general CT and crop systems that are described here were recently featured as part of the San Joaquin Valley Conservation Tillage 2005 conference farm tours that were held in June. One farm was Sano Farms, a processing tomato and cotton farm in Firebaugh, CA and the other was Sun Pacific s fresh market tomato farm, also in Firebaugh. Each of the farms that were Triticale crop planted on bed tops in conservation tillage field, Sano Farms, Firebaugh, CA 2005 Strip tilling centers of fresh market tomato beds in conservation tillage field, Sun Pacific Farms, Firebaugh, CA 2005 Transplanting fresh market tomatoes in conservation tillage field, Sun Pacific Farms, Firebaugh, CA 2003 visited uses winter crops and a spring strip tillage operation to mix crops and Strip tiller implement used in fresh market tomato beds in conservation tillage fields, Sun Pacific Farms, Firebaugh, CA 2005
At the other CT tomato farm, over-the-top herbicide was used. More details about these systems may be obtained by emailing Jeff Mitchell at mitchell@uckac.edu and requesting the DVD video that was distributed to participants of CT2005 and that describes these CT tomato systems. application. If the irrigation water delivery system is changed to either subsurface drip, or low pressure overhead delivery, we Strip tiller implement used in processing tomato beds in conservation tillage fields, Sano Farms, Firebaugh, CA 2005 Future CT tomato systems There may be long-term economic and resource conservation benefits from substantially reducing tillage in production systems relative to what is done today. To develop sustained no-till rotations that include tomatoes, a number of changes will be required with respect to optimizing management of the overall production system. Current systems, - including the approach we pursued in this study, - rely primarily on surface, or gravity irrigation systems that necessitate clean, or clear furrows for efficient and uniform water Overhead, low pressure irrigation system used in notill corn production field, Pierre, SD, 2005 hypothesize that production costs might be lower, surface residue might be left in place, soil disturbance could be avoided, and weeds might be better controlled without cultivation. These management systems, as well as other production system alternatives, are now being evaluated. Fresh market tomato field with barley crop residue, Firebaugh, CA 2003 Jeff Mitchell is a Cropping Systems Specialist with the University of California, Davis at the Kearney Agricultural Center in Parlier, California. Contact information: 9240 South Riverbend Avenue, Parlier, CA 93648; Phone (559) 646-6565; Fax (559) 646-6593; E-mail: mitchell@uckac.edu