ANALYSIS OF SOIL ORGANIC MATTER OVER MULTIPLE GROWING SEASONS AT AN ORGANIC FARM IN SOUTHEASTERN MINNESOTA

Organic matter in soil is important to agriculture because it supplies nutrients and improves soil structure, minimizes erosion, and increases the soil’s water holding capacity. In order for the nutrient cycle to be maintained, the rate of organic matter accumulation from crop residues, manure, and any other sources must equal the rate of decomposition. Modern agricultural practices speed up the decomposition of soil organic matter due to continual seasonal harvesting. Maintaining a healthy soil requires significant time and effort on the part of farmers, especially in organic farming, where organic matter is used as an alternative to synthetic fertilizers. The purpose of this research is to assess organic carbon content in a crop field and pasture at Earth-Be-Glad Farm, a certified organic farm in Lewiston, MN and to determine differences in soil organic matter within and between the soils in the different areas of the farm over two growing seasons.

Soil samples from the selected crop and pasture areas were collected after the growing season in 2012 and 2013 following a random, zigzag pattern. Two soil samples were collected at each sampling site; one to be used for organic carbon analysis and one to be used for bulk density determination. The samples for organic carbon content were obtained using a soil auger to depths between 7 and 9 inches. The samples for bulk density analysis were collected using a plastic ring. Samples were carefully placed in individually labeled Ziploc bags and transported back to Winona State University for analysis. Organic matter content of each soil sample was determined through loss-on-ignition (LOI). A known weight of each sample was heated to 360°C for 2 hours in a Barnstead Thermolyne 1400 furnace. The weight lost during the ignition was then used to calculate organic matter content for each sample. Results of this study may have implications for soil management practices at the farm.