America's farmers, over the years, have received and accepted much good advice about how to value their way of life, how to become more efficient producers, how to maintain prices and incomes, how to preserve the soil and the natural environment, and how to relate to other economic sectors and to fanners in other countries.

The combination of several measures (organic matter accumulated, soil porosity, field soil respiration, CO2 evolved during incubation, and mineral N released) shows clearly that soil biological activity was enhanced in the systems that minimized tillage. Surprisingly, the abundance of earthworms, which are considered very sensitive to damage by tillage, did not always follow the same pattern. We do not know the reason for the response of earthworms, but in part it may have been an artifact of the interaction of the collection technique with soil properties such as infiltration rate and temperature. The most dramatic improvement in porosity, organic matter accumulation and N mineralization ability came from five years' continuous growth of grass sod, underscoring the potential role of grass in sustainable cropping systems and the value of grass for soil conservation and improvement.

Quantitative data are needed to understand how alternative farming practices affect surface infiltration of water and associated surface soil properties. We used a rainfall simulator, double ring infiltrometer, small single ring infiltrometers, and tension infiltrometers to measure water infiltration for Clarion loam (fine-loamy, mixed, mesic Typic Hapludoll) and for Webster silty clay loam (fine-loamy, mixed, mesic Typic Haplaquoll) soils located on a conventionally-managed and an alternatively-managed farm in central Iowa. Steady-state measurements suggested that infiltration rates were somewhat higher for the alternative farming system. Bulk densities were sometimes lower, and volume of large pores was a little higher for the alternative farming system. Small single rings were more reproducible than rainfall simulators or double ring infiltrometers, and data trends were the same as for rainfall simulators.

Effects of soil fauna on soil quality are largely unknown. Our objective was to learn whether long-term soil management has significantly affected earthworm species and populations at two Iowa locations. Soil cores were collected in fall 1989, spring 1990, and fall 1990 from a long-term tillage study in Polk County, Iowa, involving monoculture of corn (Zea mays L.) with either no-tillage, fall disking, fall chisel plowing, or fall moldboard plowing. Species found were Lumbricus terrestris (L), Octolasion tyrtaeum (Savigny), Aporrectodea trapezoides (Duges), A. turgida (Eisen), and A. tuberculata (Eisen), with O. tyrtaeum dominant across all treatments. As the amount of tillage increased, the number of earthworms generally decreased. InBoone County, Iowa, we compared the populations of mature and immature earthworms and cocoons on two adjacent fields, one managed conventionally, the other managed with an alternative farming system for more than 20 years. The predominant species was A. tuberculata. Regardless of management practice, the most worms were found in Canisteo soil on the toeslope landscape position.

Quantitative studies are needed to separate the real and supposed benefits of alternative farming practices. Our objective was to learn how conventional and alternative practices on adjacent farms in central Iowa affected the water stability of soil aggregates. We collected samples of Clarion loam (fine-loamy, mixed, mesic Typic Hapludoll) from adjacent 16 ha fields in fall 1990 and spring 1991. Aggregate stability was determined by wet-sieving and by measuring turbidity of soil-water suspensions. The combined effects of alternative practices resulted in greater water stability of soil aggregates, higher soil organic matter content, and lower bulk density compared with conventional practices. The components of the alternative system that were mainly responsible for these differences were: rotations that included oat and hay crops; ridge-tillage; and additions of 45 Mg/ha of a mixture of animal manure and municipal sludge during the first 3 years of each 5 year rotation. The more favorable soil physical conditions, shown by increased water stability of soil aggregates, presumably will improve soil water regimes and reduce long-term soil erosion losses from the alternatively managed fields.

Four land use options—annual cropping, agroforestry, agrihorticulture, and agrosilviculture—were tried on a Land Capability Class IVs Alfisol under rainfed conditions to find a farming system that would be profitable and sustainable. The agrihorticultural system required more cash input but gave a value/cost ratio of 2.16 compared with 1.95 with annual cropping, 1.69 with agroforestry and 1.52 with agrosilviculture. Runoff was 4.9% in the agrihorticultural system, and 10.6% with agroforesty. Economic and soil health considerations led to the conclusion that the agrihorticultural system would be a sustainable land use option for the semi-arid Alfisol However, other options also are profitable, with value/cost ratios of more than 1.50. Therefore, land users can choose among several systems, depending on their desired production level and their investment capacity.

As concern about the long-term viability of our food and fiber system has grown, many agricultural research administrators, prominent scientists and policymakers have focused increasing attention on the important research and educational needs in sustainable agriculture. Colleges of agriculture should be important in meeting the challenges of sustainable agriculture; a central question is whether they are adequate for the task. This paper highlights several individual and institutional constraints that limit the ability of these colleges to address the needs: 1) assumptions and biases regarding the relationship between humans and nature, and the concept of progress; 2) the demographic characteristics, education, and experience of research scientists; 3) the specialized departmental organization of research institutions; 4) imbalances among analyses on the molecular, cell, organism and ecosystem levels; 5) emphasis on farm level analysis and technology development; 6) new agricultural biotechnologies that may overemphasize short-term, narrow technical considerations and proprietary products; 7) compartmentalization of education by discipline, and the limited informal and field experiences for students; 8) the background and education of current Extension Service agents; 9) the emphasis on economic effects in research impact assessments, to the neglect of environmental effects and social consequences for farmers, rural communities and society at large; 10) limited capability for comprehensive public policy analysis.

Despite these limitations, new research agendas and college programs are effectively addressing many needs of sustainable agriculture systems. To be more successful, these efforts must be broad-based and sensitive to a wide range of issues, and must include all participants in the system.