Matt Liebman

Improving Soil Quality

Abstract Future advancements in crop production will rely on increased understanding of ecological principles that control interactions among cropping system components. Our interest in linking soil quality and weed management derives from the belief that greater understanding of key processes and properties that define soil-weed relationships will lead to the design of agroecosystems with greater capacity and opportunity to suppress weeds. We identified seed-bank persistence, seedling establishment, and interspecific interference as key processes that affect annual weed population dynamics. We then examined how soil processes and properties can affect each of these factors and how, in turn, soil-improving management practices and cropping system design may affect weed dynamics. We established weed-related soil management objectives as: (i) reducing the persistence of seeds in the soil; (ii) reducing the abundance of safe-sites for weed establishment and the filling of available sites; and (iii) reducing ...

Abundance of carabid beetles and other ground-dwelling arthropods in conventional versus low-input bean cropping systems

Abstract The abundance and seasonal dynamics of carabid beetles and other ground-dwelling arthropods in conventional and low-input dry bean ( Phaseolus vulgaris L.) cropping systems were investigated over two field seasons in Maine, USA. In 1988, carabids and staphylinids were significantly greater in number in the low-input plots. Staphylinids and arachnids were significantly more abundant in the low-input plots in 1989. Elaterid adults were abundant in 1988, and the number in the conventional plots was 23 times higher than in the low-input plots. Multivariate analysis showed that compositions of major ground-dweling arthropods differed significantly between the two cropping systems from the early to middle season of plant growth. Individual carabid species differed between the two cropping systems. Harpalus rufipes, Pterostichus melanarius, Agonum muelleri, Clivina fossor, Carabus memoralis, Carabus auratus , and Loricera pilicornis were dominant carabid species in this study. In 1988, Pterostichus melanarius, Carabus auratus , and L. pilicornis were significantly more abundant in the low-input plots, while A. muelleri and Clivina fossor were significantly more abundant in the conventional plots. In 1989, however, only A. muelleri was significantly different between cropping systems and a significantly higher number was trapped in the low-input plots.

Research and extension efforts for improving agricultural sustainability in the north central and northeastern United States

Abstract In the north central and northeastern regions of the USA, considerable research and extension work is now being directed toward developing farming methods and whole farming systems that can reduce production costs, soil erosion and pollution by agrichemicals. These efforts have been termed low-input/sustainable agriculture (LISA) and emphasize greater use of legume-based crop rotations, animal and green manures, integrated crop/livestock enterprises, biological pest controls, mechanical control of weeds, and soil and water conservation practices. LISA activities involve most of the important crop and livestock products of each region. Farmers and non-governmental organizations have been key participants in shaping and implementing new research and extension efforts through methods that include on-farm research and demonstrations. Many land grant universities are conducting experiments to aid the transition away from chemical- and capital-intensive farming methods, and are initiating closer ties with farmers interested in or already practicing LISA methods. New curricula are being developed for student and farmer training in LISA approaches. Future research and extension efforts for LISA should make better use of ecological theory; place more emphasis on topics that involve long-term research such as agroforestry systems, crop and livestock breeding, yield-enhancing crop rotation effects and biological pest control; and more fully examine the relationships between ecologically sustainable farming methods and socioeconomic structure.