Integrated rotation systems for soil borne disease, weed and fertility management in strawberry/vegetable production

Integrated rotation systems for soil borne disease, weed and fertility management in strawberry/vegetable production

Summary

In 2014, we conducted Verticillium dahliae microsclerotia soil tests for the Santa Cruz and Salinas trials, an economic analysis for the Santa Cruz trial, an ASD webinar, and a Latino grower-targeted workshop. In the Santa Cruz site, at lettuce harvest in September 2013 (two years from ASD treatment), the number of V. dahliae microsclerotia increased in UTC plots but not in ASD and ASD+MC plots, suggesting a long-term suppressive effect of ASD. Economic analysis shows that the highest net return was obtained from broccoli- ASD+MC treatment ($30,319) followed by cauliflower- ASD treatment ($25,762). An ASD webinar and workshop were well-received.

Objectives/Performance Targets

Objective 1: To test the effects of anaerobic soil disinfestation (ASD), broccoli residue incorporation, mustard cake (MC) application, alone and in combination, on crop yields, V. dahlia suppression, weed suppression, N provision, production costs, and net returns in strawberries and lettuce grown in typical crop rotation systems on organic and conventional farms with high V. dahliae pressure. (Shennan, Muramoto, Koike, Klonsky, Milazzo, Wong, Tanimura, Noma, and Kimes. Years 1-3, Santa Cruz, Salinas).

Objective 2: We propose a series of additional experiments to optimize MC application procedures for improved yields, weed and disease suppression, and N provision in strawberries and Romaine lettuce. Specific goals are 1) to establish the optimum time between MC application and lettuce planting; 2) test the effects of MC application rate, depth of incorporation, and level of preplant fertilizer on yields, disease, and weed suppression in lettuce production; 3) as for goal 2 but for strawberries, and 4) assess the economic feasibility of MC use in lettuce and strawberries. (Shennan, Muramoto, Koike, Klonsky, Pedersen, and Kimes. Years 1-3, Watsonville).

Objective 3: To disseminate results to growers and agricultural professionals in coastal CA and beyond through a variety of approaches, including workshops, a field demonstration (at an NGO farm that works with low resource Hispanic organic farmers), field trips, YouTube, eOrganic, and written materials (All team members. Years 2 and 3).

Accomplishments/Milestones

Objective 1

1.1 Santa Cruz Site

This field trial was completed in fall 2013. In 2014, we completed soil test for viable V. dahliae microsclerotia throughout the rotation trial. Soil samples (0”-6” depth) collected on 6/15/2011 (baseline), 7/1/2011 (post-broccoli/cauliflower/fallow), 9/20/2011 (pre-ASD/MC), 10/31/2011 (post-ASD/MC), 9/28/2012 (post-strawberry), and 9/10/2013 (post-lettuce) were analyzed for viable V. dahliae population using modified Anderson sampler and NP10 semi-selective medium (Koike et al., 1994).

We also finished economic analysis for the entire rotation period. The revenue, costs of production, and net returns per acre were calculated for each treatment. A hypothetical 25-acre farm was simulated for each treatment, resulting in twelve simulations (Table 2). The revenue was based on the yields for each treatment. The cost of each farming operation was calculated based on the equipment, materials, and hours of labor used in the trial for each treatment. The net returns were calculated as the total revenue minus costs. The cost of land rental or ownership was not included. Therefore, the net returns should be interpreted as a return to management, land, and risk. All values are on a per acre basis. Work left to do for this trial is the estimation of N loss during the winter rainy seasons during strawberry growth period.

1.2 Salinas Site

This field trial was completed in summer 2012. In 2014, we completed soil test for viable V. dahliae microsclerotia throughout the rotation trial. Soil samples (0”-6” depth) collected on 6/8/2011 (baseline), 8/24/2011 (post-broccoli/cauliflower/fallow), 9/16/2011 (pre-ASD/MC), 10/25/2011 (post-ASD/MC), and 10/12/2012 (post-strawberry) were analyzed as described above. We decided not to conduct economic analysis for this site for the following reasons: 1) strawberry yield monitoring at this site was terminated in the mid-season due to the labor shortage, resulting in atypically low overall yield, and 2) lettuce crop was not planted after the strawberry due to the small plot size that could not be managed by the growers’ large equipment. Work left to do for this trial are total N analysis of plant samples and estimation of N loss during the winter rainy season.

Objective 2

The trial testing MC application procedures for improved yields, weed and disease suppression, and N provision in Romaine lettuce was conducted in 2012. Work left to do for the trial includes an economic analysis of MC application.

Objective 3

Outreach webinar on ASD was held in 2/18/2014 via eOrganic. A paper based on this project was presented at the Eighth International Symposium on Chemical and Non Chemical Soil and Substrate Disinfestation (SD 2014) held at Torino, Italy in July 2014 and a paper was published in Acta Horticultuae (ISHS). A workshop on soilborne disease management in organic strawberry production was conducted at ALBA on 9/25/2014. A survey on potential adoption of developed practices was conducted after the ALBA workshop (see table 1 below) and will be repeated along with outreach meetings/workshops to be held in 2015.

Impacts and Contributions/Outcomes

Objective 1

1.1       Santa Cruz Site

1.1.1    V. dahliae dynamics in soil

Baseline viable V. dahliae microsclerotia numbers in topsoil were rather low and averaged 0.5 per gram soil. At pre-ASD/MC application, they increased slightly to an average of 1.5 per gram soil. At post-ASD/MC application, V. dahliae was not detected at all in ASD and ASD+MC plots, whereas it was 0.3 to 0.5 for MC and UTC (P=0.15). At the end of the strawberry season, V. dahliae was below the detection limit at all plots. However, at lettuce harvest, two years from ASD/MC treatments, it increased to 2.8 in the UTC and remained significantly lower than UTC in the ASD (0.3) and ASD+MC (0.7) treatments (Table 1). This may indicate the potential of ASD to develop suppressive soil for V. dahliae.

1.1.2 Economic Analysis

For the Santa Cruz site, economic analysis was conducted for 12 different rotations (Table 2).

Costs of production: An equipment complement for the farm is developed to accommodate the practices used for each treatment assuming that the grower owned all equipment and there was a mix of new and used equipment resulting in a value of 60 percent of new costs. Equipment prices are those obtained from local suppliers. The hourly costs of operating equipment are based on agricultural engineering equations to calculate the fuel and repair costs for each piece of equipment. The number of hours for equipment use are also based on agricultural engineering equations for a 25-acre farm and not based on the hours of operation for the field trial. Field trial hours of use are always higher than actual use due to the configuration of the plots and the small size of the plots.

The material costs (water, seed, mustard cake, rice bran, fertilizer, drip tape, and gopher traps) are the actual costs realized by the research project. The cost of non-machine labor is assumed to be $10 an hour and tractor labor was $10.88. The cost of spreading rice bran and mustard cake is $10 a ton. The cost of the pre-strawberry soil treatments includes the materials, spreading, and incorporation. The costs are shown in Table 3. The cost of ASD is the lowest cost due to the high cost of the mustard seed cake compared to rice bran. Of course, the cost of ASD with mustard seed cake shows the highest cost.

The labor costs for equipment operators is based on the hours of tractor use resulting from the simulation multiplied by a factor of 1.1 to account for setup time and time moving equipment to and from the field. The non-machine labor hours for irrigation, setting out drip tape, transplanting, hand hoeing, and harvesting are based on the hours recorded on the field trial. It is assumed that there would be no economies of scale for these hand labor operations.

The cover crop costs are $331 per acre with the majority of costs ($275 per acre) going to cover crop seed, a legume cereal mix planted at a rate of 275 pounds per acre. The additional costs are for equipment and labor for planting, mowing, and spading the cover crop before each of the vegetable crops.

Harvest represents the highest cost operation for each of the crops and is hand harvested in all cases. In the trial, for each crop, all treatments were harvested at once and no records were kept to separate the hours of labor by treatment. In other words, the total hours per crop are known. The harvest costs are based on the actual hours of labor per crop in the trial and adjusted for the proportion of total yields in each treatment for each crop.

Revenue and net revenue: The revenue for each treatment is the sum of the revenue for each crop in that treatment (Table 2). The revenue is the yield per acre by the price per unit of production. For each vegetable crop the yield is equal to the field trial result for each crop and soil treatment. The strawberry yields are for each of the 12 treatments and are the total yields from 50 individual harvests. The prices of organic strawberry for the actual dates of each harvest were obtained from the Agricultural Marketing Service (AMS), Fruit and Vegetable Market News, for the Salinas-Watsonville shipping point http://marketnews.usda.gov/portal/fv. The yield for each date is multiplied by the average price for the same date to get the daily revenue. The sum of the revenue for each harvest is the total revenue. The broccoli and cauliflower from the trial were used in CSA boxes and, therefore, no direct sales occurred. No prices for organic broccoli or cauliflower were available from AMS for any shipping point or dates and so the conventional price on the harvest date with a Salinas-Watsonville shipping point is used with the assumption of a 50 percent premium for organic over conventional prices. For lettuce, all product was sold. The average price from these sales is used (Table 4).

The net revenue is the difference between the total revenue and the costs. The cost of land is not included as a multitude of ownership and lease arrangements exist. Therefore, the net return is above land and management costs.

Economic Performance. The gross revenue for each crop in each treatment and the total gross revenue for each treatment are shown in Table 5. The corresponding costs are in Table 6, and the resulting net revenue above land costs are in Table 7. Clearly, strawberry is the economic driver in the rotation with the highest gross and net revenues of all of the crops in the rotation with between 75 and 86 percent of total revenue. The costs for strawberry are also the highest of all crops primarily due to the cost of transplants and harvest. The net revenue for strawberry is roughly 90 percent of the total net revenue. Therefore, the crops and treatments before strawberry should be viewed in terms of their contribution to increased strawberry yield, as well as their individual contribution to farm income. Looking at net returns, there is no clear pattern as to whether or not strawberry did better following broccoli, cauliflower, or fallow. Strawberry performance was highest following cauliflower under ASD and MC but lowest under ASD plus MC. Strawberry performance was highest following broccoli under ASD plus MC and the untreated control. Strawberry following fallow outperformed strawberry following broccoli under ASD and also outperformed strawberry following cauliflower under ASD+MC. The highest net returns from strawberry is $29,328 per acre from the broccoli – ASD+MC treatment followed by fallow ASD+MC at $25,683 and cauliflower – ASD at $24,637 per acre. When taking the cost of soil treatment into account and subtracting that cost from the net returns to strawberry the top three stays unchanged but the order changes with broccoli ASD+MC at $24,433 ($29,328 – $4,895), cauliflower ASD at $22,258 ($25,683 -$2,379) and fallow ASD+MC at $20,788 ($25,683 – $4,895). It should be noted that all three of the highest treatments used ASD and the first and third highest used ASD plus MC. However, the difference in net revenue from strawberry is decreased by $2,528 (the additional cost of MC) between broccoli ASD+MC and cauliflower ASD when the higher cost of ASD+MC is taken into consideration. Similarly, the difference between cauliflower ASD and fallow ASD+MC increases by $2,528 when the cost of soil treatment is taken into account.

The revenue from the broccoli crop is greater than the cauliflower crop due to poor yields in cauliflower. Costs of production are identical except for harvest costs. The soil treatment should not have had an impact on broccoli or cauliflower yields because they took place after those crops were harvested. However, both vegetable crops yielded highest on the untreated control plots. Cauliflower contributed little to total net returns, while broccoli contributed between $2,075 (ASD) and $3,397 (untreated control).

Net returns from lettuce are highest following fallow for the ASD plots, broccoli for the ASD+MC plots, and cauliflower for the MC and untreated control plots. In the absence of ASD, cauliflower appears to improve the performance of lettuce over broccoli and fallow. The highest net returns for lettuce was for the fallow ASD ($3,993), followed by fallow ASD ($3,950), and broccoli – ASD+MC ($3,725). The use of ASD has a greater impact on lettuce performance than the preceding vegetable crop. Lettuce performed better with a combination of mustard cake and a preceding vegetable crop than fallow – MC and better following cauliflower for the untreated control than following broccoli or fallow.

The results of these crop impacts are that the highest net returns of all treatments is broccoli ASD+MC ($30,319) due to the optimum performance of strawberry and lettuce and the additional contribution of strawberry even with the highest treatment costs. The second highest net revenue is from cauliflower ASD ($25,762) due to the excellent performance of strawberry in this treatment. The third highest is fallow with ASD+MC ($24,407).

Overall, the net returns for treatments by crop are highest for those including broccoli plots (the average of ASD, MC, ASD+MC, and untreated control, $23,324) followed by those including cauliflower plots ($21,157) and fallow plots ($18,787). The broccoli plots have the highest average due primarily to the contribution of broccoli to the net revenue, while cauliflower plots outperform the fallow plots primarily due to their impact on strawberry and lettuce yields in the absence of ASD (Tables 7 and 8).

Turning to the soil treatments, ASD and MC alone perform best with cauliflower and ASD+MC and the untreated control perform best with broccoli. For the broccoli treatments ASD+MC performs the best, for cauliflower it is ASD, and for fallow it’s also ASD+MC. None of the crop treatments performed as well without ASD. The highest average net returns (broccoli, cauliflower, and fallow) are from ASD+MC ($24,566) followed by ASD ($23,931). The untreated control ($18,448) actually outperformed the mustard cake treatment ($17,412) due to the high cost of the mustard cake treatment ($2,543), even though mustard cake improved lettuce and strawberry yields (Tables 7 and 8).

1.2       Salinas Site

1.2.1    V. dahliae dynamics in soil

Baseline viable V. dahliae microsclerotia numbers in topsoil averaged 16 per gram soil. The numbers decreased to 3.3 to 7.3 by growing broccoli or cauliflower, or just by fallowing (cause unknown). V. dahliae remained low until post-strawberry. No significant differences were found between any treatments (Table 9).

Objective 3

3.1 eOrganic webinar on ASD

A webinar on ASD was held on 2/18/2014 with ~85 participants from the U.S. and beyond. The recorded webinar is available at eOrganic website: http://www.extension.org/pages/70271/anaerobic-soil-disinfestation-to-control-soil-borne-pathogens:-current-research-findings-and-on-farm#.VLWDsXtwFqI and YouTube: https://www.youtube.com/watch?v=_7phq_p2JQk .

3.2 Work shop at ALBA

A workshop on soilborne disease management in organic strawberry production was conducted at ALBA on 9/25/2014. The workshop mainly targeted Latino growers. We had 15 participants and simultaneous Spanish translation was provided. According to the post-workshop survey, the event was well-received by the most participants (Table 10).

Paper published:

Zavatta, M., Shennan, C., Muramoto, J., Baird, G., Koike, S. T., Bolda, M. P., and Klonsky, K. (2014). Integrated Rotation Systems for Soilborne Disease, Weed and Fertility Management in Strawberry/Vegetable Production. Acta Horticulturae (ISHS) 1044, 269-274.

• Table 6. Production and Harvest Costs ($ per acre)
• Table 3. Costs of Pre-Strawberry Soil Treatments ($)
• Table 8. Summary of Revenue, Costs, and Net Returns ($ per acre)
• Table 1. Verticillium dahliae Microsclerotia Numbers in the Topsoil of the Santa Cruz Site
• Table 2. Type of Crop Rotations
• Table 4. Prices for Broccoli, Cauliflower, Lettuce, and Strawberry
• Table 5. Total Revenue ($ per acre)
• Table 7. Net Returns Above Land Costs ($ per acre)
• Table 9. Verticillium dahliae Microsclerotia Numbers in the Topsoil of the Salinas Site
• Table 10. Summary of Evaluations for the Workshop Held at ALBA on 9/25/2014

Collaborators: