Vermicompost as a fast-acting nitrogen amendment to mitigate nitrogen deficiencies in organic vegetable production
Vermicompost is regarded as a fast acting, but expensive, nitrogen amendment. Its use may become more prevalent when Chilean Nitrate is decertified. We tested whether Vermicompost could improve productivity and whether it prevented early season deficiencies in a model crop (Swiss Chard) at Bella Farm owned by our partner Rachel Schattman. Experimental treatments were: Direct field-seeded Swiss chard with banded vermicompost, banded compost and a control which received no starter fertilizer; Swiss chard starts produced in growing medium with 10% vermicompost, 20% compost and no compost. The starts were transplanted after all start treatments had reached sufficient size for transplanting. Throughout the growing season we measured plant size. At the end of the growing season we measured harvestable biomass. ANOVA suggested that there were differences among treatments inharvestable biomass. Means were not significantly different among the direct seeded treatments although the vermicompost produced the greatest biomass. For transplants, vermicompost produced significantly greater biomass than any of the other treatments. Presently, tissue samples are being processed for nutrient analysis.
Economic Analysis was accomplished this year. In directly seed plots, applications of vermicompost was only more profitable in very sandy soils. It is not clear why this is but leaching and or droughty conditions in the sandy soil may have allowed vermicompost to outcompete the other treatments. However, when looking at a comparison between crops that were either directly seeded or planted from greenhouse starts, the vermicompost improved economic returns when starts were produced with vermicompost. It also appears that vermicompost use to produce greenhouse starts can shorten teh maturation time of swiss chard, a large benefit where growing seasons are short.
Analysis of soil nitrogen and soil water nitrogen did not show any significant differences. There are several more samples to be analyzed to confirm this finding.
1. Establishing 24 research plots at Bella Farm and 2. Direct seeding and preparation of greenhouse starts. Twenty four plots were established at Bella Farm. There were 4 replicates of six treatments: Direct field-seeded Swiss chard with banded vermicompost, banded compost and a control which received no starter fertilizer; transplanted Swiss chard starts produced in growing medium with 10% vermicompost, 20% compost and O compost.
3. Measurement of soil water NO3 and NH4, extracted from soil water samplers installed below the root zone, after storm events. Very few events produced leachate as the plots were on a Vergennes Clay soil. We noticed that during heavy rainfalls, the plots produced much runoff suggesting slow infiltration rates. However there were several events that produced leachate and samples were collected then. There was no signficant difference in soil water nitrogen among the different treatments. A similar outcome was found for soil nitrogen concentrations.
4. Estimate of plant nutrient deficiencies. Visual inspection of plants was done on the plots to detect any deficiencies and plant sizes measured to estimate growth rates.
5. Estimate of early nutrient supply rates using Plant Root Simulator samplers. Plant Root Simulators could not be installed into the plots as the clay soil was too hard and dry during the growing season. . However, we will be investigating supply rates in lab mesocosms to better understand the pattern of release from a clay loam.
6. Maintaining a project blog. The blog can be found under http://vermicompostingne.wordpress.com/
7. Presenting the project to 1 regional and 1 national conference. Presentations were given at workshops for University of Connecticut Master Composters in the Fall of 2013 and 2014. I am planning to present the results of the study at the 2015 SSSA meetings in Minneapolis, November 15- 18, 2015.
January to April 2014: Data collection continued.
April to December 2014: Grinding of plant materials, analysis of soil and water samples.
Samples were from 2013:
March 2013 – March 2014: Maintaining a project blog
March to April 2013: Establishment of plots, soil fertility analyses, installation of lysimeters, seedbed preparation, seeding crop, vermicompost, compost application in plot study.
Plots were established in June rather than April because of the heavy rains in 2013. We established plots at Bella Farm but also at two additional sites with different soils. At the additional sites we only direct seeded soils. Lysimeters were installed in June.
March 2013 to December 2013: Sampling lysimeters in plots.
Lysimeters were sampled from June to November. Early frost required us to remove the lysimeters early. Lysimeters at Bella did not yield much percolate for chemical testing. We think this was due to the clayey nature of the soil. The samples that we did retrieve are presently frozen and are awaiting analysis.
April 2013- May 2013: Seed crop in greenhouse and direct sow in field.
We started seeds in May 2013
May 2013: Transplanting greenhouse starts. Greenhouse starts were transplanted them at the end of June.
May 2013- March 2014 Interpretation of data. We found that there were significant differences among treatments but that the harvestable biomass differences were only significantly different for the greenhouse starts grown in 20% vermicompost/
June 2013 to September 2013: Visually assessing crop nutrient deficiencies, plant analyses. Plant tissue analyses are in progress. The Plant and Soil science grinding room is being refitted with safety equipment which has delayed the analyses.
September 2013 – October 2013: Harvest crop, plant analysis. Soil fertility analysis. Crops have been harvested, fresh harvest weight and plant heights have been recorded.
November 2013. Presenting data at the annual meeting of the Agronomy Society of America.
Data collection was not complete for the ASA 2013 Annual Meeting and the NOFA 2014 Winter Conference.
Impacts and Contributions/Outcomes
Some of the research results have been used to show the benefits of Vermicomposting in the UVM class “Fundamentals of Soil Science” with 92 enrolled students.
Some of the research was presented to master composters at the University of Connecticut on October 12, 2013.
My graduate student Peter Austin is preparing his thesis. He will defend at the end of February. His thesis will be uploaded with the final report.
University of /vermont
Plant and Soil Science
Burlington, VT 05405