Survey of the Nutrient Status of Organic Vegetable Farms
This project is a survey of the nutrient status of organic vegetable fields in the Northeast US. The objective is to document the nutrient status of organic vegetable fields. We are documenting the nutrient status by collecting soil samples from fields of organic growers at two times during the year. Samples are collected in June and in November. The samples in June will document the nitrogen fertility of the fields by measuring the soil nitrate concentration of the soil in the surface foot of soil. The samples collected in November will document the pH, macronutrient fertility (Ca, Mg, P, and K), and the nitrogen fertility. Two soil samples are collected in the fall: one for pH and macronutrient fertility from the surface 6-inch layer of soil, the other for nitrogen fertility from the surface 12-inch layer of soil.
Field information about the history of nutrient applications, tillage and cropping pattern will be collected from each grower. The field information will be used to place the fields into categories based on the length of time in organic production, type of nutrients, amount of nutrient application, and cropping pattern. One of our hypotheses is that we will be able to classify the soil fertility based on the history of nutrient applications on the field. The soil test results will allow us to objectively test our hypothesis.
We plan to use the results of the survey to develop an educational program about soil fertility for organic growers. Results from the first year’s survey indicate that organic growers need much education. Many fields have soil test results in the below-optimum category and many other fields have soil test results in the above optimum category. Only a small percentage of the fields have soil test results in the optimum category.
a. Each state will obtain permission from at least 3 organic vegetable farms to perform the survey of the nutrient status of their fields.
b. Each state will collect soil samples in late-spring and late-fall from at least 20 fields in 2001 and 2002.
c. Growers will complete a questionnaire about historical use of nutrients on their farm.
We collected soil samples from 31 farms. This is 16 farms greater than required by our milestones. The number of farms sampled in each state ranged from 5 to 7. We were required to sample only 3 farms per state. We collected samples from 153 fields, which is much greater than the 125 fields noted in our milestones. We also collected 6 soil samples from tunnel greenhouses. We are collecting data on the historical use of nutrients on the farms, but we have not completed this task. I expect no difficulty obtaining the historical field information.
Impacts and Contributions/Outcomes
We obtained the results from the soil sample analysis a few weeks ago. There are many results, so it is difficult to summarize in a few sentences. I will describe the soil test phosphorus results as an example because the phosphorus results are representative of the results for the other nutrients. Twenty seven percent of the fields were below optimum for phosphorus, 12% of the fields were in the optimum range, and 61% of the fields were above optimum for phosphorus. The range of values for extractable phosphorus was 1 to 1072 pounds per acre. The optimum range for phosphorus based on the modified-Morgan extractant is 14 to 20 pounds per acre.
Maine Organic Farmers and Gardeners Association
University of New Hampshire
University of New Hampshire