Reduced till cotton production systems in the San Joaquin Valley. J. P. Mitchell, D. S. Munk, B. Prys, K. K. Klonsky, J. F. Wroble and R. L.

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1 Reduced till production systems in the San Joaquin Valley J. P. Mitchell, D. S. Munk, B. Prys, K. K. Klonsky, J. F. Wroble and R. L. De Moura Abstract Conservation tillage planting and stalk management systems produced yields comparable to those of standard till practices in two back-to-back s in Riverdale, CA. These reduced till systems decreased the number of tractor operations by 41 to 53%, fuel use by 48 to 62% and overall production costs by 14 to 18%. Introduction Since the opening of the California Aqueduct as part of the Central Valley Improvement Project in 1963, (Gossypium hirsutum) has been an important throughout much of the San Joaquin Valley (SJV). It is routinely produced in rotation with other annual row s including processing tomatoes, onions, garlic, melons, and field s such as wheat and barley, particularly in the SJV s West Side region. During the period , over 400,000 acres of were harvested annually from Merced County in the north through Kern County in the south. During this same period, however, production costs for eclipsed the value of lint and seed even with the support payments that the federal government provides to producers. Improving profitability has thus become a clear mandate for sustained production in the SJV. An important management variable that producers can directly control is tillage. Preplant soil preparation, in-season weed control and postharvest stalk management are tillage-related operations in production that can account for 25% or more of overall costs (Carter, 1996). These tillage operations represent not only high energy, equipment, and labor costs, but they also reduce soil organic matter (Reicosky and Lindstrom, 1995), and are a contributing source of NOx and dust emissions (Baker et al., 2002). Adoption of conservation (CT), or reduced tillage practices similar to those that have been used successfully in other regions of the Cotton Belt, may be a viable means for increasing profitability and improving soil resource use for SJV fields. The term conservation tillage refers to a ping system that leaves at least one-third of the soil covered with residue after planting. Reduced-till systems have 15 to 30 percent residue on the soil surface after planting (CTIC, 2002). On a nationwide basis, about 3,270,587 acres, or 29.3 % of the US acreage used CT or reduced-till practices in During the last 10 years, the proportion of no-till relative to total production increased 740% with Georgia, North Carolina, Mississippi, Tennessee and Alabama being the leading no-till states (Towery, 2002). Control regulations for the pink bollworm, the lack of an inexpensive alternative for preplant weed control and unfamiliarity with CT production systems are obstacles that have prevented greater adoption of reduced tillage for SJV (Carter, 1996). While these are still formidable issues, a number of recent innovations have made the prospect of developing reduced tillage options for achievable. The introduction of reduced-pass rebedding equipment that

2 facilitates pink bollworm plowdown compliance, the advent of various herbicide-resistant varieties and the availability of high surface residue cultivators and planters have made the prospect of developing reduced tillage systems for realizable in California s current production environment. Farm tillage study To evaluate and refine a number of possible CT systems for, we initiated a study with Borba Farms in Riverdale, CA in the fall of Borba Farms is a 13,000 acre diversified farm located in western Fresno County that produces a variety of s including, processing tomatoes, wheat, alfalfa, sugar beets, garlic and onions. Three replications of seven planting and postharvest stalk management systems were set out in 30-inch beds across a 12-acre field (Table 1). A standard management approach (System 1) employing typical currently used approaches to planting and stalk management was established as a reference, or control plot. Prior to each of the two s in the study, a winter cover of barley (Hordeum vulgare) was grown across the entire experimental field in an effort to add organic matter to the soil and to improve tilth. The soil in this field is a Grangeville fine sandy loam. Borba Farms routinely uses small grain cover s as a means to improve overall soil quality and reduce stand losses caused by blowing sands or inadequate bed moisture in their coarser-texture fields. These cover s were seeded on November 1, 2000 and November 15, 2001 after about a 3-month period of growth they were sprayed with and then disked prior to reestablishing planting beds in the standard tillage system in late March of each of the following springs. Three planting systems, no-till, ridge-till and strip-till were evaluated alongside the conventional or standard tillage system. In the no-till system, the only tillage is the soil disturbance in a narrow slot created by coulters or seed openers at planting. Ridge-till is a reduced disturbance planting system in which s are planted and grown on ridges (the equivalent of peaked beds) formed during the previous growing season and maintained with shallow in-season cultivation equipment (Photo insert 1). In the ridge-till system, planters sweep away, or sheer off residues and soil in the seed line, but do not disturb much of the inter-row soil surface. In strip-till, coulters cut residues ahead of subsoiling shanks that loosen the soil from a few to as many as 14-inches ahead of a planter (Photo insert 2). In each of these CT systems, only a small percentage of the soil surface is disturbed unlike the broadcast tillage, or land preparation operations that are typically used in conventional tillage systems. Prior to using each of these three planting systems, the cover s were either sprayed with and chopped with a flail mower (Systems 1, 3 and 6), or only sprayed with (Systems 2, 4 and 7) to evaluate planting performance in these different cover residue management systems (Photo insert 3). A six-row 30inch John Deere 1730 (Moline, IL) planter was used in Systems 1, 2, 5, 6 and 7, and a Buffalo 8000 Ridge-Till Planter (Fleischer, NE) was used in Systems 3 and 4. Each planter was calibrated to plant 58,000 seeds per acre with an expectation for final plant populations of at least 40,000 plants per acre.

3 Table 1. Preplant and postharvest operations used in tillage systems evaluation at Borba Farms, Riverdale, CA, System 1 System 2 System 3 System 4 System 5 System 6 System 7 No-till Ridge-till Strip-till Standard No-till Ridge-till Strip-till chopped cover cover till no-chop no-chop no-chop cover chopped chopped Chop cover Disk Disk Chisel Disk List beds Plant Ring roll Chop cover No-till plant with JD 1430 planter stalks and/or No-till plant with JD 1430 planter stalks and Chop cover Ridge-till plant with Buffalo 8000 planter stalks and/or Ridge-till plant with Buffalo 8000 planter stalks and Chop cover Strip-till seed bed Plant stalks and Strip-till seed bed Plant stalks and/or Disk Disk Subsoil /

4 Photo 1. Ridge till planting into barley cover, Riverdale, CA Borba Farms Agromanager, Bob Prys to right. Photo 2. Strip till planting into barley cover, Riverdale, CA 2001.

5 Figure 3. Cover management prior to planting at Borba Farms, Riverdale, CA, Herbicide sprayed cover near leaf center. Herbicide sprayed and chopped cover at right and disked in cover at left of sprayed strip A global positioning system (GPS) tractor guidance system was used for the subsequent planting in 2002 to maintain the integrity of the tillage plots. Following harvest of the 2001 and 2002 s, stalks in System 1 were shredded using a flail mower. These control plots were then disked twice, ripped to a depth of about 18 inches, and then planting beds were reestablished using a (Bigham Brothers, Lubbock, TX) shank fitted with bed shaper shovels. Postharvest stalk management in each of the other systems consisted of shredding, root pulling with a Sundance implement (Coolidge, AZ), and relisting beds using the parabolic shank without shovels (Photo insert 4) in 2001, and shredding and then subsoiling/listing using disc-blade cultivator tools mounted at the back of the implement in the fall of The CT systems thus differed from the standard tillage system in terms of both preplant and postharvest tillage operations (Table 1) and were managed from the general principle of reducing tillage to the greatest extent possible while using generally available equipment and maintaining yields at desired levels.

6 Photo 4. Bigham Brothers (Lubbock, TX) bent leg shank fitted with "Go Devils" used for stalk management at Borba Farms experimental study, Riverdale, CA, 2002 Monitoring tillage system performance Cotton stand establishment was monitored at about one month following planting in each year by counting the number of emerged seedlings along 100 feet lengths/sections in each plot. Standard plant mapping procedures were used during each season to characterize growth and development. Yield was determined by machine harvesting and weighing lint and seed from the center 4 or 8 rows in each 6 or 12 row plot, respectively. Six-pound harvest samples from each plot were ginned at the University of California Shafter Cotton Field Station and gin turn out, or the lint percentage of the total sample by weight, was determined. Surface residue was determined in December 2002 by counting the number of residue pieces with a diameter greater than or equal to 2mm at each one foot increment along a 100 foot length in each plot. Records of all field operations, including implement width and tractor horsepower used, were maintained by Bob Prys, the supervising agronomist at Borba Farms. Crop productivity Cotton plant populations generally adequate for optimal yields were achieved by each planting system in both years of our study, with the exception of ridge-till (Systems 3 and 4) in

7 2002, when we set the seeding depth too low. Our test of the ability of these conservation tillage planting systems to achieve adequate stands in herbicide-sprayed and chopped cover (Systems 2, 4 and 6) or herbicide-sprayed cover (Systems 3, 5 and 7) was only conducted in 2001 due to the fact that the cover was chopped in all systems in However, a slight reduction in plant stands was seen in both the no-till (system 2) and the ridge-till (system 4) planting systems in the sprayed only cover relative to the sprayed and chopped cover in that year (Table 2). Table 2. Average number of plants per acre for tillage system evaluation at Borba Farms, Riverdale, CA, 2001 and 2002, and percent of the field with plant skips greater than 3 ft. based on 100 ft. of sampled row in Cover / tillage system (Percent of field with > 3 ft plant skips) System 1 41,200 45, System 2 34,500 42, System 3 39,500 21, System 4 34,500 19, System 5 34,200 44, System 6 39,000 38, System 7 46,800 39, Because stand establishment was generally adequate except in the 2002 ridge-till system, this single-year evaluation of cover management approaches requires additional testing to determine the relative benefits of herbicide spraying alone, or herbicide spraying in conjunction with chopping prior to CT seeding. Such follow-up studies are now underway. In-season plant monitoring data can be useful in identifying contrasting growth and development patterns between tillage treatments that affect performance. Differences in surface residue cover for instance, can modify microclimate by changing the surface radiation reflected and soil sensible heat flux. Cover residues remaining on the soil surface are highly reflective and often result in lower surface soil temperatures thereby reducing plant growth. Plant mapping measurements conducted in June found shorter plants with fewer fruiting branches for tillage treatments having high surface residue content, (Table 3). However these differences were minimal by mid-july. Mid- and late-season plant monitoring also included the evaluation of nodes-abovewhite-flower (NAWF), an indicator of earliness. The conventional tillage treatment was found to have consistently lower values for NAWF, indicating the conventional tillage treatment expressed enhanced earliness and alternative tillage systems delayed maturity. In locations where earliness is favorable, this can be seen as a drawback to the use of alternative tillage practices.

8 Table 3. Conservation Tillage System June 11 In-Season Plant Height and Fruiting Nodes on June 11; Height, Fruiting Nodes and Nodes Above White Flower on July 17 and August 8 at Borba Farms in Height Fruiting Nodes July 17 Height Fruiting Nodes NAWF August 8 Height Fruiting Nodes NAWF Yield data from this study reveal a number of important management strategies that may be used in further developing and optimizing CT production systems in the SJV. In both years, strip-till prior to planting, a more aggressive seedbed preparation practice, had the most consistent yields, averaging 1307 pounds of lint / acre in 2001 and 1251 pounds / acre in In the sandy soil at this experimental site, strip-tillage provided seedbed conditions that were fully adequate for establishment, growth and development. In 2001, the two strip-till systems (Systems 6 and 7) yielded more lint than the standard till control (System 1). System 2, no-till planting into standing herbicide-killed cover residue, had the lowest yields of the CT systems in In 2002, the decreased plant populations in the two ridge-till systems corresponded to significantly lower lint yields relative to the standard till system and the other CT systems. In that year, an extra ring roller pass was made in System 1, That operation put seed in close contact with moist soil resulting in a boost in seedling emergence, early season vigor and yield. Postharvest stalk management Elimination of the pink bollworm (Pectinophora gossypiella) (PBW), a pest that eats bolls and has caused billions of dollars of damage to the industry, has been a longstanding priority of SJV producers. A major strategy in the SJV for PBW eradication has been to maintain a minimum host-free period each year from December 21 through March 10.

9 Following harvest and prior to the host-free period, plants are typically shredded, undercut and mixed with surface soil in compliance with plowdown requirements established by state law and enforced by Agricultural Commissioners in each -growing county. Standard postharvest stalk management that ensures compliance consists of shredding aboveground plant material to about four inches above the soil line, undercutting the stalk so as to sever the stalk from the roots, disking the residue and the soil one or more times, ripping the soil, and listing beds for the subsequent. Other eradication strategies used in conjunction with postharvest stalk management, include the release of sterile moths in fields to disrupt normal mating, the use of pheromones that confuse the male moths and make it difficult for them to locate females, and the use of transgenic pest-resistant seed that reduces larval feeding. In this study, we evaluated two systems for reduced pass stalk management. At the end of the 2001, a sequence of operations that involved shredding, root pulling and subsoiling using a bent leg shank was used. This series of operations was effective in killing plants throughout each of the CT systems and was given a provisional clearance by the Kings County Agricultural Commissioner. Following the 2002, the same series of events was repeated with the only difference being that the was fitted with sets of rotary harrow Go Devils mounted behind to throw up beds in a single-pass operation. This sequence of postharvest operations was also highly successful in killing plants and was deemed in compliance with PBW stalk management requirements by the local Agricultural Commissioner. Practical lessons This study revealed the short-term feasibility of using conservation tillage planting and stalk management systems to produce in California s SJV with yield, quality and pest management outcomes that are adequate for this site s production standards. The study was conducted in a commercial production field and thus represents a reasonable scale of operation for current production systems in the SJV. Lint yields of each of the alternative tillage systems equaled or exceeded the yield of the standard tillage system in the first year, while 2002 standard tillage system yields were numerically, though not statistically higher than the alternative tillage systems. The ridge-till systems had significantly lower yields in 2002 due largely to the problems encountered with reduced plant stands. While these alternative tillage systems all delayed maturity (Table 4) and reduced the earliness of the fruit set, there were adequate heat units in the 2002 season to compensate for any differences with no significant influence on yield. Differences in yield were however significant with the 2 ridge-till systems but were caused primarily by the inadequate plant stand that occurred in the 2002 season. Yield is an important determinant of farm profitability, but reducing inputs and operational costs are other means to affect a farm s bottom line. The CT systems that were evaluated in this study (Table 5) reduced the number of tractor operations used to produce a by 41 to 53% depending on system. This corresponded to an estimated reduction in fuel use of 48 to 62%, and a reduction in overall production costs of 14 to 18%. By extrapolation and based on companion studies we have recently completed, we would expect that

10 a corresponding decrease in direct particulate matter emissions would be achieved by the CT alternatives relative to the conventional tillage system. Table 4. Pounds of lint / acre for tillage systems evaluation at Borba Farms, Riverdale, CA 2001 and 2002 Cover / tillage system System abc 1258 a System bc 1215 a System ab 709 b System abc 809 b System c 1311 a System a 1278 a System ab 1223 a Table 5. Comparison of cover and tillage system tractor operations, estimated fuel use and production costs per acre FARMING SYSTEMS Times over field Gallons of fuel Total operating costs $237 $199 $195 $199 $195 $204 $200 Converting to reduced till production alternatives, however, requires a number of significant operational changes that must be negotiated, and each of these requires an up-front investment in additional management in order to be successful. The operating agronomist at Borba Farms committed considerable time and thought to each of the management issues he faced during the course of this work. His behind-the-scenes trial and error innovation is not borne out in any of the cost estimates we have presented here. This component was indispensable for the success of this study. For major changes to be implemented in overall agricultural production systems such as those that we evaluated here, attitude is often cited as a prerequisite for success (Bradley, 2002). Developing an attitude for change may become increasingly popular if more successful examples of CT production systems are demonstrated

11 (Mitchell et al., 2002). More studies are needed at this site to better assess the yield stability of each of these alternative systems and to work out issues related to obtaining more uniform plant stands in the alternative tillage systems, and at other sites with higher yield potentials and contrasting soil types. Jeff Mitchell is Cooperative Extension Specialist in the Department of Vegetable Crops and Weed Science at the University of California, Davis. Dan Munk is a Farm Advisor in Fresno County. Bob Prys is Agromanager with Borba Farms in Riverdale, CA. Karen Klonsky is Cooperative Extension Specialist in the Department of Agricultural and Natural Resource Economics at the University of California, Davis. Jon Wroble is a Cooperative Extension Field Technician in Fresno County and Rich DeMoura is a Production Cost Analyst in the Department of Agricultural and Natural Resource Economics at the University of California, Davis. We graciously thank the generous and unwavering support of Borba Farms that enabled this study. References Arroues, K.D. and C.H. Anderson Jr Soil survey of Kings County California. Soil Conserv. Serv., U.S. Dept. Agric. 233 pp. Baker, J., R. Southard and J. Mitchell Agricultural dust production in standard and conservation tillage systems in the San Joaquin Valley. In. Proceedings Conservation tillage 2002: Research and Farmer Innovation Conferences. September 17, 2002, Davis, CA. September 19, 2002, Five Points, CA. Bradley, J. F., th Annual Southern Conservation Tillage Conference Proceedings. Auburn, AL. June Carter, L. M Tillage. In Cotton Production Manual. University of California Division of Agriculture and Natural Resources Publication Pages CTIC, National Crop Residue Management Survey. Conservation Tillage Information Center, West Lafayette, IN. Mitchell, J.P., E.M. Miyao, J.J. Jackson, M.G. Martinez and K. Schlosser Developing Information on conservation tillage production systems in California. In Proceedings Conservation Tillage 2002: Research and Farmer Innovation Conferences. September 17, 2002, Davis, CA. September 19, 2002, Five Points, CA. Reicosky, D.C. and M.J. Lindstrom Impact of fall tillage on short-term carbon dioxide flux. In. (Eds.) Lal, R., J. Kimble, E. Levine and B.A. Stewart. Soils and Global Change. CRC Lewis Publishers. Towery, D National Crop Residue Management Survey. Conservation Tillage Data. Conservation Technology Information Center. W. Lafayette, IN.