Variety Evaluation, Selection and Management for Organics Vegetable Systems
Influence of Compost Application and Variety on Yield and Quality Variables of Organically Grown Edamame, Lettuce, Processing Tomato, and Potato
Senay Ozgen and Matthew D. Kleinhenz
Department of Horticulture and Crop Science
The Ohio State University
Ohio Agricultural Research and Development Center (OARDC)
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.
Materials and Methods
The study includes numerous varieties of edamame-type soybean, lettuce, potato, processing tomato, and popcorn. 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. 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 untreated. The compost used in 2004 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.
Land use in this project was certified for organic production.
Plot Maintenance. 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.
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, Carry, 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.
Information for all crops planted in 2004, except popcorn, are presented here. 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 into the field. 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.
Plot Establishment. Eight edamame varieties were planted on May 12. Two-row plots of each variety were established with a four-row soybean planter. Each row was 20 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 10-112.
Data Collection. At maturity, data were collected from plants in the center 16 ft of the two center 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 3 or more beans. Yield was recorded on each group. Sub-samples of 2- and ≥-bean pods were collected and stored for further quality analysis and sensory evaluation. Samples for sensory evaluation were blanched before being placed at -20 C until analysis. 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.
Plot Establishment. Fifteen varieties of leaf and romaine-type lettuce were planted on May 28. The field was covered with black cloth ground cover soon after soil preparation in order to eliminate weed growth. 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. 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 placed in a drying oven for additional analyses after fresh weight was taken. Both leaf and stem fresh weight were taken before leaves and stems were placed in the drying oven prior to measures of moisture content.
Plot Establishment. Twenty genotypes were planted on June 3, 2004. One row plots were established by hand. Each row was 10 ft long with 5 ft between rows and 15 in. between transplants. Total yield was taken from twenty genotypes while marketable yield was recorded for thirteen genotypes.
Data Collection. At maturity, fruits were harvested from each replication. They were sorted and weighed as a group of healthy red, healthy green, immature, and defective. Five individual samples from these groups (except defective) were placed into a drying oven after individual weight was taken from them. Brix (% solids), pH, acidity from the healthy red fruits were recorded.
Plot Establishment. Seed for fourteen varieties were cut on May 17, 2004 and allowed to cure until planting on June 3, 2004, with a one-row mechanical planter. Each row was 10 ft long with 38 in. between rows and 1 ft between seed pieces.
Data Collection. Vines were mowed on September 30 when most of the vines were dead in the field. Potatoes were field cured until mechanical harvest on October 6. After harvest, potatoes were placed in darkened storage at 7 ºC for approximately 21 days and then graded for size and external quality.
Significant treatment effects on yield and quality were noted in all crops. Additional analyses will resolve the independent and interactive effects of variety and compost application.
Except for lettuce, higher yields of all crops were recorded in plots amended with compost. The yield of all potato and processing tomato and six of eight edamame varieties was greater in composted-amended than non-amended plots. Overall, marketable yield ranged from 30.3-176.9 g/plant, 1.2-4.0 kg/plant, and 8-191 cwt/A in edamame, tomato, and potato, respectively.
Contrary to other crops, lettuce head weight was generally lower in compost-amended than non-amended plots, although this was not the case for ‘Freckles’ and ‘SVR 5636’. The highest head weight (2.1 kg) was observed on ‘Green Forest’ grown without compost while the lowest head weight (0.3 kg) was recorded on Mendoza grown with compost.
In edamame, no clear trends were noted for treatment effects on the number of pods in 500 g or fresh weight of 100 beans.
Treatment effects were significant for processing tomato fruit pH, acidity, and % solids (Brix).
Yield of B-size potatoes tended to be higher in plots amended with compost, compared to plots of the same variety grown without compost.
Data from the 2004 study year are published in six tables within the following publication:
Ozgen, S. and M.D. Kleinhenz. 2004. Influence of compost application and variety on yield and quality variables of organically grown edamame, lettuce, processing tomato and potato. In: Midwest Vegetable Variety Trial Report for 2004, Bulletin No. B824, Dept. of Horticulture, Office of Agr Res Progs, Purdue Univ., West Lafayette, IN. pp. 219-226.
Also, project plots were featured and available for direct observation by farmers in the OSU Organic Food and Farming Education and Research Program, Ohio Ecological Food and Farming Association, and Innovative Farmers of Ohio Field Day at the OARDC on July 1, 2004. The Field Day attracted participants from around Ohio and the 0.3-h presentation on the project accrued 13.5 client contact-hours.
In 2004, the first year of the project, we aimed to:
1. Verify which crops and varieties to include in the study.
2. Establish plots of these crops and varieties in soils differing in organic management (with, without compost application).
3. Collect and report comprehensive data on variety performance, including a range of people in the food system (e.g., farmers, chefs) in data collection.
4. Share project findings.
We obtained performance data on eight varieties of edamame soybean, fifteen varieties of lettuce (spring and summer plantings), thirteen 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.
Impacts and Contributions/Outcomes
To our knowledge, LNC03-236 was the first project of its type in the state and region to:
1. Complete rigorous tests of the performance of multiple varieties of five vegetable crops when grown under contrasting certified-organic conditions.
2. Publish data from these evaluations in a well-known and widely distributed compilation of variety trial reports.
3. Employ the research plots in which performance was tested in direct outreach activities such as field days and farmer visits.