Variety Evaluation, Selection and Management for Organics Vegetable Systems
Organic vegetable farming is increasing in Ohio and the Midwest. To be successful, organic farmers must consistently select and manage varieties best suited to their production and market conditions. Research-based information regarding variety performance in the field and market can greatly assist farmers in this regard. The Organic Vegetable Variety Evaluation, Selection, and Management Project was initiated to provide research-based information regarding crop and variety selection to organic farmers to help improve the understanding of variety-x-compost interactions in organic vegetable systems.
Materials and Methods
Land use in this project was certified for organic production.
Plot Maintenance. Crops were planted in separate fields or areas within each field and the separate and combined effects of compost application and variety on yield and crop quality variables were tested using a randomized complete block design with four replications per treatment (compost application-variety combination).
Soil amendment (compost and dairy manure) was applied using a manure spreader and incorporated by disking before planting in one-half of the plots for each crop, while the remaining plots were unamended. The compost in 2006 was approximately 1.31, 0.71, and 3.94 percent N, P, and K by weight, respectively.
For transplanted crops (lettuce and processing tomato), organically grown transplants were seeded in the spring, allowed to grow 6 weeks in a climate-controlled greenhouse, and hardened off before planting in the field.
Weed pressure was minimized with machine and hand cultivation. Disease and insect pressure were minimized by the use of organically labeled crop protectants, if populations exceeded anticipated economic thresholds based on scouting.
For all crops, harvest readiness was estimated for individual varieties from published maturity information and visual examination of four plots per entry. Varieties were harvested individually as they matured.
Statistical Analysis. Data reported here are subsets of those collected. In this analysis, treatment refers to individual combinations of variety x compost application (+/-). Analyses of variance (ANOVA) were performed to test amendment effects on dependent variables for each crop by using the General Linear Model Procedure of Statistical Analysis System (SAS, version 7, Cary, N.C.). Effects were considered significant if P ≤ 0.05. After completing the ANOVA, Fisher’s LSD test (a=0.05) was used to compare treatment mean values.
Plot Establishment. Eight edamame varieties were planted on May 31. Two-row plots of each variety were established with a four-row soybean planter. Each row was 16 ft long with 27 in. between rows. The planter delivered 150 seed/row. Due to low germination, the number of plants in each row ranged from 3 to 52.
Data Collection. At maturity, data were collected from plants in the center 10 ft of one of the two rows of each plot. Pods were removed from the plants and weighed (total yield). Pods were then sorted into unmarketable and marketable groups, with marketable pods also sorted into those containing 2 beans and those containing 3 or more beans. Yield was recorded for each group. Sub-samples (500 g) of unsorted marketable pods were taken and the number of pods counted. Fresh weight (g) of 100 beans was also recorded on the same sub-sample. Only seven varieties are represented here.
Plot Establishment. Fifteen varieties of leaf and romaine-type lettuce were planted on May 23 and again in the summer on September 5-7. The field was covered with black cloth ground cover soon after soil preparation in order to eliminate weed growth. The cloth ground cover remained in place until after the second planting. Three-row plots were established by hand. Each row was 15 ft long with 12 in. between rows and 10 in. between transplants. Each row contained 18 transplants.
Data Collection. At maturity, nine marketable heads were removed from the center 14 heads in each plot. Four of these heads were weighed. Leaves then were separated from the stem of these four heads and placed in a drying oven for additional analyses after fresh weight was taken. Both leaf and stem fresh weight were measured before the leaves and stems were placed in the drying oven prior to measures of moisture content. The remaining five heads were individually cut in half longitudinally. Half was placed immediately at –20 C until further chemical analysis. The fourth and fifth leaves were removed from the remaining half. Measurements were taken on the fourth leaf while petiole sap measurements were taken from the fifth leaf.
Plot Establishment. Seed for fourteen varieties were cut on May 11 and allowed to cure until planting on May 25, with a one-row mechanical planter. Each row was 25 ft long with 38 inches between rows and 1 ft between seed pieces.
Data Collection. Vines were allowed to senesce naturally prior to harvest. Potatoes were field cured until mechanical harvest on October 9. After harvest, potatoes were placed in darkened storage at 7 ºC until sizing and grading on November 7.
Plot Establishment. Six varieties of popcorn were machine-planted into four-row plots on May 25. Rows were 26 ft long with 36 inches between rows and 10 inch between seed at planting.
Data Collection. Popcorn was harvested on October 6 and October 9. Husks were removed by hand. All ears were allowed to dry down to a moisture measuring 12-16% before being shelled mechanically. A total weight and moisture level of each plot was recorded at the time of shelling. Yield data are reported here. Popping tests are underway.
Plot Establishment. Twenty genotypes were planted on May 25. One-row plots were established by hand. Each row was 10 ft long with 5 ft between rows and 12 in. between transplants. Total and marketable yield was taken from all twenty genotypes.
Data Collection. At maturity, fruits were hand harvested from the center 5 plants from each plot. Direct measures of total fruit weight were recorded for all genotypes. A 33% by total weight sub-sample was then sorted and weighed as a group of healthy red, healthy green, immature, and defective. Five individual samples from these groups (except defective) were retained for individual measurements. In addition, 9 healthy red fruit were retained for measures of Brix (% solids), pH, and acidity (not reported here).
Totals of 35, 42, 45, 6, 40, tests (# varieties x # variables) of the effect of compost within each variety were completed for edamame, potato, lettuce, popcorn, and processing tomato respectively. Of these tests, 6 (edamame), 32 (lettuce), 4 (popcorn), 8(tomato), were statistically significant (a= 0.05).
The data suggest that regardless of crop and whether compost is used, variety selection is likely to affect yield. The data also suggest that compost application tends to increase yield in most varieties of the crops tested but to an extent depending on variety.
We appreciate the support of the USDA-CSREES Sustaniable Agricutural and Research Education (SARE) Program (North Central Region), the Ohio Vegetable and Small Fruit Research and Development Program, The OSU/OARDC, OSU Extension, and The Department of Horticulture and Crop Science.
We would also like to thank Sonia Walker, Sasha Bogdan, Eileen Ramsay, Dr. Ann Chanon, Steven Haba, Julie Lawson, Colleen Robson, Deb Miller, Todd Barnett, Andrew Salerno, Jerrod Weyer, Rachel Miller, Chuck Pierce, Bob Napier, John Elliot, Bruce Williams, Bill Bardall, Dr. David Francis, Troy Aldrich, Lee Duncan, Kesia Hartzler, Yoder’s Produce and Supply, and Ron Dessecker for their excellent technical assistance.
Donations from Harris Seeds, Seminis Vegetable Seed, and Ohio Earth Food, Inc. are greatly appreciated. Assistance from Johnny’s Selected Seeds, Maine Potato Growers Association, Ronniger’s Potato Farm, and Wood Prairie Farm is also appreciated.
Data from the evaluations outlined above are available in the following publication:
Sutter, M. and M.D. Kleinhenz. 2006. Compost application and variety effects on yield and quality variables of organically grown edamame, lettuce, potato, popcorn, and processing tomato. In: Midwest Vegetable Variety Trial Report for 2006, Bulletin No. B18048, Dept. of Horticulture, Office of Agr Res Progs, Purdue Univ., West Lafayette, IN. pp. 117-124.
These data were also shared in four presentations:
1. Two presentations given at the Mid-Atlantic Fruit and Vegetable Convention on 1/31/2006.
2. Presentation during a session of the City Fresh Market Gardener Training Program on 2/28/2006.
2. Presentation during the OSU Organic Food and Farming Education and Research (OFFER) Program, Ohio Ecological Food and Farming Association, and Innovative Farmers of Ohio OARDC Field Day on 8/24/2006.
In 2006, on-farm evaluations of cabbage variety performance were included in the project. The cabbage evaluation integrated the expertise of OARDC, two seed companies, a farmer, and a sauerkraut manufacturer. The work is summarized below in an abstract of a presentation that will be delivered at the 2007 Meetings of the ASHS.
Plant Population, Variety and Sampling Effects on Organic Kraut-type Cabbage Plant and Head Traits
Kleinhenz, M.D. and M. Sutter
Plant population and variety effects on crop yield and quality in organic, kraut-type cabbage are poorly characterized. On-farm study can help close this gap in the literature. In 2006, eight varieties (17698, Kaitlin, Krautman, Megaton, SG3378, Superkraut, TransAm, XBC2329) were transplanted to an organically-managed, non-irrigated field in Luckey, OH on 1 June in single, replicated, randomized 200-m rows located in two adjacent blocks. In-row spacing of 35.6 cm (block 1) and 40.6 cm (block 2) and between-row spacing of 84 cm gave 33.5 (block 1) and 29.4 (block 2) thousand plants/ha. At head initiation (22 August) and crop maturity (10 October), five consecutive plants or heads were removed from four areas within each row separated by 15 m and transferred to refrigerated storage at the OARDC. Then, a total of fourteen plant and head variables were measured, most on individual heads. Plant and head traits were more consistently and strongly affected by variety than by plant population. Brix levels varied with the position in the head from which samples were taken. Eight of fifty-six tests (7 variables x 8 varieties) of the influence of plant population were significant (α = 0.05) while variety significantly affected all but one variable (tissue mass/ha at head initiation), regardless of plant population. Among varieties, the influence of plant population was inconsistent for all variables except yield and whole-head Brix. Yield tended to be highest at 29.4 thousand plants/ha, although the effect was significant for only two varieties. Brix levels were measured in four regions of 320 individual heads: outer half-top half, outer half-bottom half, inner half-top half, inner half-bottom half. Regardless of plant population and variety, Brix values were greater in tissue taken from the bottom- versus top-half and the inner- versus outer-half of mature, trimmed heads. However, this effect was significant for only the top-bottom comparison. Whole-head Brix values tended to be highest at 33.5 thousand plants/ha, although the effect was significant for only two varieties.
In 2006, the third year of the project, we aimed to:
1. Establish plots of multiple varieties of five major vegetable crops in soils differing in organic management (with, without compost application).
2. Continue comprehensive assessments of variety performance, including a range of people in the food system (e.g., farmers, chefs) in data collection.
3. Continue distribution of project findings throughout the region.
In on-station plots, we obtained performance data on seven varieties of edamame soybean, fifteen varieties of lettuce (spring and summer plantings), twenty varieties of canning-type tomatoes, six varieties of popcorn, and fourteen varieties of potato. A well-known chef and owner of a restaurant specializing in local and seasonal cuisine participated in the evaluations.
In on-farm plots, we obtained performance and plant and head characteristic data on eight varieties of processing-type cabbage when planted at 10K and 12K plants per acre.
Results were distributed throughout the region in publications, presentations, and field days.
Impacts and Contributions/Outcomes
The impact of this work is increasing and is likely to maximize after the project is officially
completed. In this project, we generate and distribute information on the performance of
vegetable varieties when grown under a range of organic production conditions. This information is critical to all in the food system (especially farmers and buyers) who work to match varieties, production conditions and market forces. When such matches are made, increases in profit potential and opportunities for environmental stewardship follow. Rapid changes in variety selection can be difficult since buyer resistance, unfamiliarity and questions about availability can slow farmers’ adoption of new varieties. So, the format of this project has been key to its success: new and currently popular varieties of multiple crops were grown in different ways. This has allowed us to provide farmers with a range of information that they can use in variety selection and management. For example, while some may be reluctant to change varieties, the information that we provide may help them be more successful with the varieties they grow. To date, this project has raised awareness about variety selection issues and options among farmers and non-farmers and provided rare research-based information on genetic-environmental management in organic vegetable systems. To our knowledge, the SARE program is among a very small number of sponsors of this critical type of work.