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. This project was initiated to provide research-based information regarding crop and variety selection to organic farmers and to help improve the understanding of variety-x-compost interactions in organic vegetable systems.
Materials and Methods
Land used in the project was certified for organic production.
Plot Establishment and 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 (composted dairy manure) was applied using a manure spreader and incorporated by light disking before planting in one-half of the plots of each crop, while remaining plots were unamended. The compost used in 2005 was approximately 2.7, 1.4, and 2.9 percent N, P, and K by weight, respectively, and had a total C/N ratio of 11.8/1.
For transplanted crops (lettuce, 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. Tomato and lettuce were drip irrigated as needed, based on estimates of soil moisture using the hand-feel method.
Information for all crops planted in 2005, except edamame, is presented here. For all crops, harvest readiness was estimated for individual varieties from published maturity information and examination of plots. Processing tomato varieties were harvested individually as they matured while all varieties of lettuce, popcorn and potato were harvested on the same day specific to the crop.
Statistical Analysis. Data reported here are subsets of those collected. Data presented here follow from analysis (ANOVA, LSD) of the effect of variety within compost application (+/-) and the effect of compost application within variety for each crop. The General Linear Model Procedure of Statistical Analysis System (SAS, version 8.2, Cary, N.C.) was employed and effects were considered significant if P ≤ 0.05 (ANOVA). Alpha was set at 0.05 in completing Fisher’s Least Significant Difference tests.
Plot Establishment. Fifteen varieties of leaf and romaine-type lettuce were transplanted to the field on May 26-27. The field was covered with black cloth ground cover soon after soil preparation in order to eliminate weed growth and transplants were set through holes cut in the cloth. 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. On June 30, nine mature, marketable heads were removed from the center 14 heads in each plot. Five of these were individually cut in half longitudinally and placed immediately at –20 C until further chemical analysis. Fresh weight was recorded from four consecutive heads. Leaves were separated from the stem of these four heads and both sample types were dried separately before dry weights were recorded (i.e., leaf and stem fresh and dry weight and percent moisture were recorded separately).
Plot Establishment. Six varieties of popcorn were machine-planted into four-row plots on May 18. Rows were 26 ft long, with 30 in. between rows and 10 in. between seed at planting.
Data Collection. On October 6 kernel moisture measured 12-16%; therefore, all ears were removed the same day from the center two rows of each plot. Husks were removed by hand and kernels
were mechanically shelled and kernel moisture and weight for each row recorded. Yield is reported here. Popping tests are underway.
Plot Establishment. Seed for fourteen varieties were cut on May 20 and allowed to cure until being set into single-row plots with a one-row mechanical planter on June 1. Each row was 20 ft long with 38 in. between rows and 1 ft between seed pieces.
Data Collection. Vines were mowed on September 21, although most vines had senesced naturally 2 to 3 weeks previously. Potatoes were field cured until mechanical harvest on October 5. After
harvest, potatoes were placed in darkened storage at 7 ºC until sizing and grading on October 18 and November 9.
Plot Establishment. Twenty genotypes were transplanted by hand to the field on June 7. Single-row plots were 10 ft long, with 5 ft between rows and 15 in. between transplants. Drip irrigation tape was placed within 6 in. of the center of each row after transplanting and soil moisture was maintained at adequate levels through a combination of rainfall and irrigation.
Data Collection. At maturity, all fruit were hand-collected from all plants in each plot. Direct measures of total fruit weight were recorded for all genotypes. For eight genotypes (O 7983, OX 23, OX 325, U 2008, PS 696, H 9423, GEM 611, GEM 818), 33% by weight of all fruit were sub-sampled, sorted into healthy red, healthy green, immature, and defective categories, and counted and weighed. Using the mean percent by weight of healthy red fruit from these eight genotypes, marketable yield was estimated for the remaining twelve genotypes. In addition, for all genotypes, 18 healthy-red fruit were retained for measures of Brix (% solids), pH, and acidity (not reported here).
Variety within compost for each crop significantly affected all variables reported, except for percent leaf moisture in lettuce.
A total of thirty, six, forty-two, and forty tests (# varieties x # variables) of the effect of compost within each variety were completed for lettuce, popcorn, potato, and processing tomato, respectively. Of these tests, sixteen (lettuce), two (popcorn), one (potato), and eighteen (processing tomato) were statistically significant (α = 0.05). Lettuce head fresh weight and popcorn, potato, and processing tomato yield tended to be higher in plots receiving compost compared to non-amended plots.
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 tests but to an extent depending on variety.
We appreciate the support of the USDA-CSREES Sustainable Agriculture 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 Troy Aldrich, Lynn Ault, Bill Bardall, Todd Barnett, Sasha Bogdan,
Christine Curtis, Ron Dessecker, Lee Duncan, John Elliot, Dr. Ron Fioritto, Dr. David Francis, Aparna Gazula, Bill Haddad, Kesia Hartzler, Dave Kelly, Erica Kovacik, Audrey Malosh, Scott McIntyre, Bob Napier, Greg Smith, Sonia Walker, Jerrod Weyer, and Bruce Williams for their excellent technical assistance.
Donations from FedCo Seeds, Harris Seeds, Johnny’s Selected Seeds, Nunhems USA, Inc., Ohio Earth Food, Inc., and Wannamaker Seeds are also greatly appreciated. Assistance of the AVRDC, Coastal Valley Seeds, Harris Moran Seed Co., Ohio Potato Growers Association, Orsetti Seed Co., Rijk Zwaan Seed Co., Ronninger’s Potato Farms, Rupp Seeds Inc., SeedEx, Seminis Vegetable Seeds, Inc., Siemer Enterprises, Inc., Sunseeds, and Synergene is also appreciated.
Data are available in the following publication:
Ozgen, S. and M.D. Kleinhenz. 2005. Influence of compost application and variety on yield and quality variables of organically grown lettuce, popcorn, potato and processing tomato. In: Midwest Vegetable Variety Trial Report for 2005, Bulletin No. 17810, Dept. of Horticulture, Office of Agr Res Progs, Purdue Univ., West Lafayette, IN. pp. 175-181.
Project research plots were also featured and available for observation by farmers and others 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 held on 9/7/05. The field day was attended by farmers and others from throughout Ohio and the 0.5-hr presentation on the project reached 43 client contact-hours. Project findings were also shared during invited presentations at the Ohio Ecological Food and Farming Association Annual Conference (3/5/05), OFFER-Organic Agriculture Consortium Project meeting, and Ohio Master Gardener Conference (10/8/05), totaling 105 client contact-hours. Members of the Organic Agriculture Consortium represent Iowa State Univ., North Carolina State Univ., Ohio State Univ., UC-Santa Cruz, Tufts Univ., and the USDA.
In 2005, the second 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.
We obtained performance data on 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.
Results were distributed throughout the region in publications, presentations, and field days.
Impacts and Contributions/Outcomes
The impact of this work is emerging and is likely to maximize after the project is officially completed. Organic farmers require information in many areas in order to be successful. The focus of this project is to generate and distribute information on vegetable variety performance under a range of organic production conditions. Buyer resistance, unfamiliarity and questions about availability slow farmer adoption of new varieties. As information developed in this and related projects becomes prevalent, all in the food system, including farmers, will be better equipped to match varieties, production conditions and market forces. Increases in profit potential and opportunities for environmental stewardship will follow. To date, this project has raised awareness about variety selection issues and options among farmers and non-farmers.