Nutrient management on organic vegetable farms: A research and education program for sustainable soil fertility management in southern New England
In this first year of the project, we focused on our goal to create a routine soil test procedure for managing soil fertility on organic farms. We have identified a need for soil tests that are specifically targeted to the needs of organic vegetable growers. One test that shows much promise for organic farmers is the Illinois Soil N Test (ISNT). The ISNT analyses soil for amino-sugar N, a fraction of soil N that is easily mineralizable and that may become available for the crop during the growing season (Khan et al., 2001). The test has been calibrated for conventionally-grown corn in Illinois (Khan et al., 2001), New York (Klapwyk and Ketterings, 2006), and Connecticut (unpublished data). It has also been shown to predict N responsive sites where liquid or composted dairy manure is applied to corn agroecosystems (Klapwyk et al., 2006). Because of its ability to predict readily mineralizable N, it may have great utility for organic fields which have received compost or manure for several years to decades. Recently, we assessed soils from 22 regional organic farms and found significant positive linear relationships between N mineralization and organic matter content and autumn NO3 values. This preliminary data suggests that further research would offer critical insights into managing soil fertility on organic farms throughout the region.
Due to a delay in 2009, this was the first year of work on this project, starting in Spring 2010. In this initial year, the research team collected soil samples from seventeen organic farms in New Hampshire (6), Massachusetts (7), and Connecticut (4). Members of the research team met with farmers in early spring to discuss the project plans and to identify 3-5 fields appropriate for sampling. Data has been collected from three sampling dates (early, mid-, and late season) and is now being analyzed. Research team members will discuss results with farmers in late winter, so that their nutrient management approach will reflect current soil conditions.
• Performance target: From the 225 organic vegetable farmers who participate in the project, 50 farmers will use individual field records, nutrient management tools, soil testing procedures, and, where applicable, stalk tests to reduce N applications by 30 pounds per acre and P2O5 applications by 30 pounds per acre to achieve optimal levels on 540 acres. These practices will lead to more efficient use of soil amendments linked to crop needs and existing soil fertility, which in turn will reduce the amount of nitrate in groundwater, reduce phosphorus loading to freshwater systems, and decrease the cost of production by $12 per acre for N and $12 per acre for P2O5.
Our work in 2010 is in support of this performance target; however, as anticipated, we have not achieved the performance target in this first year.
• Milestone 1: A group of 25 organic vegetable growers will use two new nutrient management planning tools to assess their fertility needs: (1) an NRCS-compliant tool which utilizes a combination of spreadsheets for vegetable farmers to develop nutrient management plans; (2) a web-based program for predicting soil organic matter and P changes from applications of manure and compost. Participating farmers will gain critical insights about their soil fertility and employ modified nutrient management strategies as a result.
We will work with our farmers prior to our 2011 sampling season using 2010 soil results, and then again in winter 2012, using data from the previous 2 sampling seasons. We decided on this approach in order to maximize use of data and to engage farmers more fully in the data analysis.
• Milestone 2: Among the group of 25 organic vegetable farmers, 5 farmers will participate in an on-farm research trail to test the responsiveness of sweet corn to N additions. We will assess the efficacy of the ISNT, PSNT, and the cornstalk nitrate test for their ability to distinguish between N responsive and non-responsive sweet corn sites. Farmers will gain an appreciation for research design and data collection and will be active participants in the research.
Field season 2010 did not include the on-farm sweet corn trials. This aspect of the research has been shifted to 2011 and 2012.
The following milestones are being planned (but have not yet happened). Here, the dates have been updated to reflect the shifted time frame.
• Milestone 3: Before the second growing season, the group of 25 organic vegetable growers will use data from the previous year in the nutrient management tools. Farmers will adjust their nutrient management approach to reflect current conditions of their soils. Apr ‘11-Oct ‘11.
• Milestone 4: During the second year of on-farm research trials, the continuing group of 5 organic growers will participate in the data analysis. After collecting 2 years of data on the efficacy of the ISNT, PSNT, and the cornstalk nitrate test for their ability to distinguish between N responsive and non-responsive sweet corn sites, we will work together to interpret the data. April ‘12-December ‘12.
• Milestone 5: The first regional nutrient management workshops will be offered in January of year 3 for 200 farmers who use organic inputs. Two workshops will be offered in each state for a total of six workshops. Approximately 30-35 farmers will participants in each workshop. From among the core group of 25 farmers who participated in the on-farm research, 12 will serve as peer educators in the first regional workshops, with two farmer educators per workshop. The core group of 12 farmer educators, in conjunction with other project investigators, will help participants identify critical information and resources they need for nutrient management. Jan ‘12
• Milestone 6: The second regional nutrient management workshops will be offered to the 200 farmers who participated in the first workshops, in the manner described under Milestone 5. The second workshops will build upon the first. Participants will be involved in interpreting the results of the on-farm research projects and trials from years 1 and 2 and in developing a customized soil nutrient management plan. Oct ’12.
• Milestone 7: Based on the on-farm research and collaborations with Dr. Mallory in Maine, a set of peer-reviewed articles regarding soil fertility with biologically-based nutrient inputs will be submitted. We will also create a set of New England Regional Fact Sheets on Nutrient Management for Farms using Biologically-based Nutrient Inputs. These regional fact sheets will be used by 100 farmers using biologically-based nutrient inputs. Jan ’12-Dec ’12.
• Milestone 8: A follow-up survey of all project participants will be conducted in year 4 to assess current soil management practices and utilization of soil testing resources. From the 25 on-farm participants, we will determine the extent of behavior change and profitability using baseline data from our soil testing database, and the follow-up survey in year 4. Reduction in environmental impacts will be assessed using literature values for N and P loading, on a farm-by-farm basis. Mar ’12-Oct ’12
Work in the first year of the project was focused on identifying interested farmers in Connecticut, Massachusetts, and New Hampshire, working with those farmers to identify fields to sample, and collecting soil samples in early, mid- and late-growing season. In this first year of the project, we focused on our goal to create a routine soil test procedure for managing soil fertility on organic farms. In addition to the standard soil test values (e.g., pH, OM, P, K, N), we assessed soils using the Illinois Soil Nitrogen Test (ISNT). We conducted N mineralization experiments, in order to calibrate the ISNT for soils which receive organic inputs. Much of the sample analysis was completed at the University of Maine analytical laboratory. Because of the variety of soils, management histories, and organic matter content collected from our locations, the UMaine laboratory has requested to do additional analyses using our soils. They are working on a new soil carbon dioxide (CO2) analysis that can be used to quantify soil microbial activity (Haney et al., 2008). This is an excellent opportunity to link our data with a possible new technique for quantifying soil microbial activity, and we will work with Bruce Hoskins at University of Maine to analyze the data once it is available.
Some of the stated milestones were modified to fit with field and logistical considerations. We were able to sample at 17 organic farms in Connecticut, Massachusetts and New Hampshire. We decided to shift using the nutrient management tools to this year and next year. This will allow farmers to engage more fully with the data, and to make decisions based on their characterized soil conditions. We also decided to shift the sweet corn trials to field seasons in 2011 and 2012, using data from 2010 to inform our experimental design.
Impacts and Contributions/Outcomes
We collected soils in the 2010 growing season and have completed analytical analyses in order to complete the following activities. We are currently analyzing the data. Our goals are:
• to assess the ISNT for organic farms by surveying a wide variety of organic farms, collecting soil data, and performing N mineralization incubation;
• to illustrate the utility of the in-season NO3-N test for determining whether soil N availability is adequate for crop production, especially in the case of the common practice of double-cropping on diversified organic farms;
• to assess P levels across a wide number of sites with varying compost or manure addition history to determine the relationship between nutrient management practices and P levels;
• to determine the N mineralization potential of organic soils and explore relationships between N mineralization and the ISNT, NO3-N levels over the growing season, or P levels.
As noted in the previous section, our soil samples will be used in another research trial, at the University of Maine. The soils will be used to calibrate a new CO2 analysis that can be used to quantity soil microbial activity (Haney et al., 2008). Results from this new collaboration will be analyzed to determine the applicability of this new analytical method to biologically-managed agroecosystems.
1. R. L. Haney, W. H. Brinton, and Eric Evans. 2008. Estimating Soil Carbon, Nitrogen, and Phosphorus Mineralization from Short-Term Carbon Dioxide Respiration. Comm.Soil Sci. and Plant Analy., 39: 2706–2720.
2. Khan, S.A., R.L. Mulvaney, and R.G. Goeft. 2001. A simple soil test for detecting sites that are nonresponsive to nitrogen fertilization. Soil Sci. Soc. Am. J. 65:1751-1760.
3. Klapwyk, J.H., Q.M. Ketterings, G.S. Godwin, and D. Wang. 2006. Response of the Illinois soil nitrogen test to liquid and composted dairy manure applications in a corn agroecosystem. Canadian J. Soil Science 86 (4): 655-663.
5. Klapwyk, JH and QM Ketterings. 2006. Soil tests for predicting corn response to nitrogen fertilizer in New York. Agronomy Journal. 98:675-681.
Cooperative Extension Educator
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University of Massachusetts
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