The effect of food processing waste on cover crop growth and subsequent cash crop production in a certified organic vegetable operation

Final Report for ONE03-007

Project Type: Partnership
Funds awarded in 2003: $9,930.00
Projected End Date: 12/31/2003
Matching Non-Federal Funds: $2,322.00
Region: Northeast
State: Maine
Project Leader:
Mark Hutchinson
University of Maine Extension
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Project Information


An economical source of plant-available nitrogen is one of the limiting factors in organic production in the Northeast. Food residual products are a nutrient source that can be used to fertilize cover crops, to improve soil health. This investigation focused on the ability of Sorghum Sudan grass (Sorghum bicolor x S. bicolor var. sudanense) to scavenge nitrogen from a food residual. In 2002, two food residual treatments, fish processing residual and bean processing residual, were compared for use as a soil amendment for Sorghum Sudan grass. Impacts of these were tested on cover crop biomass, percent plant tissue N, and soil nitrate availability. A randomized complete block experiment was conducted in two locations with four replications. Soil amendments were applied at rates equivalent to 0, 45, 90,135 kg/ha of N in late June. A Sorghum Sudan cover crop was planted immediately after the soil amendment application. Soil nitrate levels did not differ between treatments. Dry and wet biomass of the cover crop were measured in late fall. Whole-plant tissue analysis was measured to determine the amount of nitrogen the plant was able to scavenge. There was a linear relationship between the amount of N added to soil and % plant nitrogen for fish residual (r2=0.85) and bean residual (r2= 0.64). There was no linear relationship between amount of N added and plant biomass. Based on these results, it appears that food-processing residual had no significant impact on soil nitrate levels or plant biomass. There was an effect on the percent of plant nitrogen.

In 2003, lettuce, broccoli and melons were planted on the same plots to determine if the food residual and cover crop had a residual effect on soil nitrate. No significant difference was found across treatments in any of the cash crops in 2003. Yields did mirror 2002 soil nitrate data.


The organic vegetable industry is expanding rapidly throughout the United States. Plant-available nitrogen is often the plant-limiting factor for organic growers. Maine’s food processing facilities produce large volumes of residual during July, August, and September. These materials contain significant amounts of nitrogen. Organic growers are interested in determining the agronomic viability of using this material as a nutrient source for growing summer cover crops and to conserve nitrogen for the following season’s cash crop. This investigation focused on the ability of Sorghum Sudan grass (Sorghum bicolor x S. bicolor var. sudanense) to scavenge nitrogen from a food residual and conserve the nitrogen for the following season.

Project Objectives:

To determine the agronomic viability of food residual as a nutrient source, primarily nitrogen, to feed cover crops to build soil health and to conserve nutrients.

To determine if food residual applied before a summer cover crop increased the amount of nitrogen available the following season and ultimately increase farm profitability.

Specific Performance Targets

Develop two completely randomized replicated field research sites in conjunction with our cooperating farmer.

Collect and evaluate soil nitrate levels throughout the growing season, yield data from three different crops, (lettuce, melons, and broccoli) and obtain economic data.


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  • Mark Hutton


Materials and methods:

Year One:

In June 2002, replicated trials were established using a randomized complete block design with four replications measuring 2 x 3m. at two locations: Goranson Farm, Dresden, ME and Highmoor Farm, University of Maine Agricultural Experiment Station, Monmouth, ME.

Nitrogen treatments of 0, 45, 90,135 kg/ha of total N were provided by one of two sources, fishwaste residual or baked bean residual.

Biweekly soil nitrate levels were collected from May 2002 through October 2002 and again from April 2003 through August 2003.

A Sorghum Sudan (Sorghum bicolor x S. bicolor var. sudanense) cover crop was planted on June 28, 2002.

Cover crop fresh, dry weights and total plant N were determined from a randomly selected 0.37m2 quadrant sampled on September 24, 2002.

Year Two:

Established plots were planted to a cash crop as described below.

Research results and discussion:

Goranson Farm:

‘Winter Density’ (Lactuca saliva Bibb/Romaine) Lettuce transplants were started and grown in the greenhouse and transplanted into triple rows 0.35 m apart and 0.35 m within row spacing on June 16, 2003.

‘Early Queen’ (Cucumis melo L.) transplants were started and grown in the greenhouse and transplanted (0.5m within row spacing) into raised plastic beds on June 16, 2003.

The middle eight lettuce plants in the center row were harvested on August 14th, 2003. Wet and dry weights were measured. Woodchucks and cutworm destroyed the bean residual trial. No useable data was collected. Wireworms reduced the melon planting to less than 25% stand. No data was collected.

Highmoor Farm:

‘Early Queen’ (Cucumis melo L.) transplants were started and grown in the greenhouse and transplanted (0.5m within row spacing) into raised plastic beds on June 16, 2003.

‘Gypsy’ broccoli (Brassica oleracea italica group) was direct seeded into double rows 0.5m apart on June 20, 2003 and thinned to stand 0.15m within row spacing.

All plots were harvested on September 11, 2003. Melons and broccoli were harvested from the center 2m of each plot, counted and weighed.

Results and Discussion

Soil NO3 results

Soil NO3 did not significantly change during the 2002 growing season as a result of applying either fish or bean residue at rates equal to 0, 45, 90,135 kg total N /ha in early summer.

No differences in cover crop biomass were detected. However, there was a significant difference in plant tissue nitrogen in the sorghum-sudan cover crop following an application of 135 kg/ha of N from fish waste. Significant differences accord following an application of 90 kg/ha and 135 kg/ha of bean waste.

Results from Goranson Farm 2003 Cash Crop

There was no significant difference in lettuce yield in 2003 at the Goranson Farm. Soil nitrates were not significantly different across treatments in 2003.

Results from Highmoor Farm 2003 Cash Crop

Melon yields were not significantly different across treatments in 2003 for either fish or bean waste.

There was no significant difference in Broccoli yields at any treatment or application rate.

Research conclusions:

Application of fish or bean waste at rates equal to 45, 90 or 135 kg total N / ha did not result in increased soil NO3 levels as measured by soil nitrate test.

Using food residuals as a N source did not increase cover crop biomass.

Differences were observed in the cover crop’s ability to accumulate N as greater amounts of food residual were applied.

No significant differences were found among cash crop yields in 2003. However the cash crop yield data mirrored the soil nitrate data from 2002 for both fish and bean residuals.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

A demonstration plot was developed at Maine Common Ground Fair in 2002 for Small Farm Field Days. Approximately, one hundred and fifty people had the opportunity to see cover crops growing with food residual as a soil amendment.

Presentations were made to the following audiences on the utilization of food residuals in cover crop production for organic vegetable production.

Field Day at Highmoor Farm, August 2002, 43 growers attended.

Maine Organic Farmers and Gardeners’ Association meeting during the Maine Agricultural Trade Show, 85 growers and service providers, January 2003.

1st Annual Winter Vegetable Meetings held in Alfred and Augusta, 58 growers and service providers, March 2003.

Soil Health Workshop at Goranson farm in July of 2003, thirty-three people attended the workshop. Three people have made additional inquiries about utilizing these products for organic production.

Field Day at Highmoor Farm, September, 2003 58 growers attended and service providers.

American Society for Horticultural Science Centennial Conference in Providence, Rhode Island, A poster session presentation on this research, over 1500 participants, October 3-6,2003.

Farmer to Farmer Conference sponsored by the Maine Organic Farmers and Gardeners’ Association and Cooperative Extension, 76 participants, Bar Harbor, Maine November 1, 2003.

New England Vegetable and Berry Conference, Soil Health concurrent session, 220 participants, Manchester, NH, December 16, 2003.

Scheduled: New England Regional In-Service Training for Agriculture Service Providers Portsmouth, NH, February 5, 2004.

Project Outcomes

Project outcomes:

A second objective was to determine the economics of utilizing the food residual as a nitrogen source for cash crop production. The scale of operation made determining financial figures difficult. Long trips for small quantities of materials created disproportionate transportation cost. It is clear that the transportation and on-farm handling of the material were very inefficient.

Farmer Adoption

A more efficient method of unloading, applying, and incorporating the materials needs to be developed in order for farmers to successfully utilize these products.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

This project needs repeating for collaboration of results over different growing conditions. During the project the farmers raised questions about mineralization rates of the material.

“What is the mineralization rate of food residual and food residual compost?” A winter greenhouse mineralization study was conducted in collaboration with Dr. Tim Griffin at the USDA Agricultural Research Service in Orono to evaluate the material used in the SARE project. The research showed that direct application of food residual resulted in the mineralization of plant available nitrogen before the majority of plant uptake occurred. Most of the plant available nitrogen (PAN) was leached below the plant root zone. In contrast, preliminary composted food residual provided PAN at the time most required by the plant. More research needs to address this area of compost as a nitrogen source for organic production. What is the optimal composting time to meet organic standards and maximize PAN for direct field soil applications?

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.