Changes occurring to minimally disturbed soil and to plant covers

Authors: Russo, Vincent; Zibilske, Larry; Webber Iii, Charles

Submitted to: Journal of Environmental Monitoring and Restoration
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2011
Publication Date: 2/27/2012
Citation: Russo, V.M., Zibilske, L.M., Webber III, C.L. 2012. Changes occurring to minimally disturbed soil and to plant covers. Journal of Environmental Monitoring and Restoration. 7:68-77.

Interpretive Summary: There are options in the way producers can transition from conventional to organic production. One method could include minimum disturbance of soil while excluding prohibited methods and materials in the 3-year transition period. In a field that was in perennial pasture, and which supported grasses and broadleaf plants, monitoring sites were established that were sampled at least on an annual basis. Changes in nutrients and microbial activity in the soil were determined at different depths. Changes in nutrient levels in the plant cover were also determined. Changes in nutrient content and microbial activity occurred over the 3-year period. Nutrient content in covers decreased over time. Changes over time did not appear to be related to weather conditions which were monitored over the period. Use of minimal soil disturbance probably has few disadvantages, but the lack of soil manipulation and addition of organic compounds from roots of the cover crop may prolong establishment of non-pasture crops under an organic production system when the soil is converted from perennial pasture.

Technical Abstract: During the transition to organic production certain materials and practices, as described under US law, can not be used. During the transition period growers may, or may not, disturb the soil. There is little known about changes that occur if the soil is minimally disturbed during the transition to organic. A producer’s field that had been in perennial pasture was designated for future use in organic specialty crop production. With the cooperation of the producer the land was managed by grazing of cattle and occasional mowing of the cover during the transition period without addition of external inputs. Within the field sites were designated and samples of soil down to 60 cm obtained over a three year period. Microbial activity and nutrient content of the soil and plant cover were determined. Comparison samples from the same soil type in another location that had been under continuous cultivation were included during the second year. Air temperatures and precipitation were continuously recorded. Over the three year period there were changes in soil microbial activity and nutrient content. However, these did not appear to be universally related to air temperatures or precipitation. In the continuously cultivated soil most measures of microbial activity appeared to be higher than in the minimally disturbed soil. Some soil nutrients were also higher in the continuously cultivated soil, although the nitrate-nitrogen level was lower. Nutrient content in covers generally decreased over time. Minimal disturbance of soil probably has few disadvantages, but lack of soil manipulation and deposition of organic compounds from roots of the cover crop may prolong establishment of non-pasture crops under an organic production system when the soil is converted from perennial pasture.