Roughly 50% of the world’s surface area has been converted to grazed land or cultivated crops. Landscape conversion is often dramatically influenced by tillage which has been blamed for reduced carbon storage, increased freshwater sediment loads, and decreased soil biodiversity. Our objective was to determine which aspects of current agricultural systems lead to degradation of soil fertility and lower yield efficiencies compared to perennial grasslands. Building on recent work in Kansas which showed that unfertilized prairies yield N levels comparable to wheat while storing greater C and N, we asked two questions: Are low levels of soil N and C in the croplands artifacts of obsolete agricultural practices or are they inherent to the production of annual crops? What changes in soil processes, mechanisms and biological communities occur when prairies are converted to annual crops? In order to answer these questions a never cultivated prairie meadow in Kansas was divided into two treatments 1) native prairie meadow and 2) never-tilled, no-till annual cropland converted from native prairie using herbicides.
Results/Conclusions

Without tillage, conversion from native tall grass prairie to annual agriculture reduced soil fertility and changed composition of soil biota after only 3 years. We found that readily oxidizable carbon and microbial biomass were significantly lower in annual never-tilled cropland versus prairie. Nematode community structure was significantly different between prairie and never-tilled cropland and nematode assemblages were dominated by basal taxa typical for disturbed, nutrient poor conditions.