Impacts of organic farming on soil organic matter.
Abstract
Soil health is a critical component for developing Organic 3.0, which strives to place organic as a model sustainable food systems. However, the extent to which organic can contribute to maintaining and improving humic substances (HS) across the United States has not been investigated. It is especially important to take HS and its components into account when examining soil parameters, because humic substances is closely associated with soil health attributes. We measured the percent total soil organic matter (%SOM) and the percentages of sequestered SOM in the form of long-lived humic acids (%HA) and fulvic acids (%FA) in 1040 conventional farm soils from 48 United States and 683 organic farm soils from 38 United States to determine if and quantify how much organic farming leads to more SOM sequestration in comparison with conventional farming practices. The average%SOM is 7.37 for conventional and 8.33 for organic samples.%FA ranges are 0.08 to 2.20 and 0.04 to 14.8 for conventional and organic farm soils with mean values of 0.26 and 0.65, respectively. The%HA ranges are 0.17 to 23.0 (mean 2.85) for conventional and 0.25 to 48.9 (mean 4.1 for organic samples). The mean%humification (i.e. sequestration) is 45.6 for conventional soils and 57.3 for organic. Except for water retention, which is statistically better in conventional soils, all other comparisons show improved levels in organic farm soil samples. This information is critical for the development of Organic 3.0, because it provides clear information for in tracking the effects of changes in farm soil management practices over space and time, which can aid us in moving our current agricultural system toward sustainability.