Long-Term, Large-Scale Systems Research Directed Toward Agricultural Sustainability

A long term, large-scale study comparing five farming systems was initiated in September 1998 at the Center for Environmental Farming System located near Goldsboro, North Carolina, USA. The systems include: (1) conventional short-rotation best management practices (BMP); (2) cropping and animal husbandry (C/A); (3) organic production system (ORG); (4) plantation forestry/woodlot system (FOR); and (5) old field successional ecosystem (SUCC). Data reported hitherto were observations from the first five years of the study. In general, soil samples from the C/A-p and SUCC were found to have higher air-dry aggregate stability than the ORG and BMP-ct (conventional tillage) and -nt (no-tillage) subplots. Bulk density was lowest in ORG and highest in C/A-p. Analysis of phospholipid fatty acid composition of soil microbes revealed the divergence of the microbial community structure among ecosystems with high microbial diversity in organic and no-tillage systems. The numbers of free-living bactivores and fungivores, apparently responding to organic sources of nitrogen including a winter cover crop, were higher in organic than in BMP-ct systems in July but not in other dates in 2001. The numbers of predatory nematodes were highest in the FOR-bw and the SUCC systems. Cumulative abundance of soil microarthropods was higher in the ORG than in BMP-ct, FOR-bw and pasture C/A-p subplots, but not different from BMP-nt and SUCC systems. This pattern was driven by the abundance of soil mites, which comprised approximately 70% of the sampled arthropod community. Collembola and all other arthropods comprised approximately 20 and 10% of the soil arthropod communities, respectively. In the first two years, the organic system was most effective in enhancing soil microbial biomass C and N among the transition strategies. By the third year, soil microbial biomass C and N in the reduced-input transition strategies were significantly higher than those in the conventional (averaging 32 and 35% higher, respectively), although they were slightly lower than those in the organic (averaging 13 and 17% lower, respectively). Data also suggest that an organic transition strategy that first replaces synthetic fertilizers with organic sources may be the best approach for growers from transition to organic.