Differences in fine root production and C allocation among perennial cropping systems in contrasting soils of the upper Midwest

Background/Question/Methods

Fine roots play a key role in the global carbon (C) cycle because the majority of C accumulating in the soil is the result of fine root production and turnover. Moreover, in agricultural systems fine roots are especially important because they represent the primary source of C input to soil. Here we explore fine root production and C allocation across a suite of perennial cropping systems grown for biofuels over a five-year period in contrasting soils. The systems, established in 2008, included switchgrass, miscanthus, poplar, native grasses, early successional, and restored prairie.  Our objectives were to determine how fine root production and C allocation differs across these systems during the establishment phase compared to the established production phase and to determine how plant diversity relates to fine root production. In-growth cores were deployed in replicated systems in south central Wisconsin (mollisols) and southwestern Michigan (alfisols). 

Results/Conclusions

Fine root production differed between the two sites (P<0.05) in every year except 2011. In general, fine root production was greatest in Michigan, where alfisols are lower in soil organic matter and other soil nutrients compared to Wisconsin mollisols. Within locations, fine root production strongly differed across perennial cropping systems in both establishment and established production phases (P<0.05). In Michigan, the native grass and restored prairie systems typically had the greatest amount of fine root production (P<0.05). In the first two years in Wisconsin, there was little difference in fine root production, but after crops fully established, the native grass system typically had the greatest amount of fine root production (P<0.05). Results suggest that the native grass system typically had the greatest fine root production and systems with higher plant diversity had greater fine root production compared to the monoculture systems.