Potato acreage and total production in Maine have declined steadily since the 1960s. In 1991, a University of Maine research team established a large-scale, long-term, comparative study of three factors that form the foundation of productive potato cropping systems: soil management, pest management, and variety choice. This study, the Potato Ecosystem Project, included 96 main plots (5.8 ha total) and near-by “component studies.” The project contrasted amended vs. unamended soil management strategies; conventional vs. reduced-input vs. bio-intensive pest management strategies; and disease and stress susceptible vs. tolerant potato varieties. Given recent concerns over resistance to pesticides and increasing costs of agricultural chemical inputs, the reduced-input and bio-intensive pest management systems provided encouraging results. Weed growth was similar in the conventional and reduced-input systems. Colorado potato beetle thresholds were exceeded less often and their densities were lower in the bio-intensive system than in the reduced-input and conventional systems. Lady beetles, which are major aphid predators, were more abundant in the bio-intensive pest management system compared with the reduced-input and conventional systems in 5 of the 6 years. Tuber yield and quality were maintained at a high level in the reduced-input system, although difficulties with plant disease, nutrient and weed management contributed to significantly lower yields in the bio-intensive pest management system. Economic analysis indicated that from 1993 to 1996, the reduced-input system had a greater return over variable cost (avg. $973 ha-1) than the conventional (avg. $890ha-1) and bio-intensive pest management systems (avg. $578ha-1). The amended soil management system achieved rapid improvements in soil quality: soil organic matter, water stable aggregates, potassium, and soluble inorganic phosphorus contents increased while requirements for synthetic fertilizers were reduced. These improvements in soil quality enhanced late-season crop vigor, canopy duration and tuber quality, and increased yields by 13% and 30% over the unamended system in 1994 and 1995, respectively, but not in 1996. Improved crop vigor in the amended soil management system also benefited weed control efforts by encouraging a more weed-suppressive potato crop. In the biointensive pest management system, in which weeds were controlled mechanically, the amended soil management system had less weed biomass than the unamended soil management system in 1994 and 1995. Conversely, the amended soil management system consistently increased flea beetle populations and, in one of two years, the incidence of Rhizoctonia. The choice of potato variety also affected pest dynamics. Total aphid density (all aphid species considered together) and almost all disease ratings were higher on ‘Superior’ than ‘Atlantic’ potato.

Conventional and organic semidwarf Granny Smith apple production systems were compared during three years of conversion to certified organic management. Because of differences in fruit load with hand thinning compared with chemical thinning, apple tonnage was higher in the organic production system (OPS) in 1989 and 1991. The organic system was higher than the conventional system in number and weight of fruit per tree, but smaller in average fruit size. Using grower-receivedfarmgate premiums of 38% (1990) and 33% (1991) for unsorted, certified organic apples, comparative cost accounting showed greater net return per hectare for the OPS. The OPS required higher material and labor inputs in all years.

Greater terminal growth in the conventional production system (CPS) in 1991 was the only significant difference in growth indicators between systems. N was generally higher in leaf and new wood bark tissues in the CPS. P was generally higher in the leaf and new wood bark tissues in the OPS. No decline in yield was associated with increased weed biomass in the OPS. There was no difference in fruit damage caused by codling moth between production system treatments (codling moth granulosis virus and pheromone-based mating disruption vs. synthetic insecticide). In 1991, secondary lepidopterous pests (apple leafroller and orange tortrix) caused greater fruit scarring in the CPS. In all years, tentiform leafminers caused greater leaf damage in the CPS. Apple leafhopper density and leaf damage were greater in the OPS in 1990 and 1991.

Soil nutrient levels showed few significant changes during conversion to organic management. Soil bulk density and water holding capacity were useful indicators of changes in soil physical characteristics. Potentially mineralizable nitrogen andmicrobial biomass-C were more sensitive indicators of system change than total N or organic C. Two soil biological ratios, the respiratory ratio and biomass-C/total organic-C, were similar in the two production systems. Earthworm biomass and abundance increased in the OPS in the third year. The introduction of Lumbricus terrestris into the OPS greatly increased litter incorporation rates.

Synthetic inputs have become the norm in cash grain production in the Midwest U.S., but do they really increase profitability compared with low-input production methods? This study reports a comparison of cash grain yields, quality and profitability under two management systems, low-input practices and conventional practices. The crop sequence was corn, soybean, and wheat - medium red clover green manure. Low-input practices included crop rotation, manure, and mechanical weed control. Conventional practices added starter fertilizer, side-dress N for corn, early spring topdress N for wheat and herbicides to the low-input practices. The conventional inputs increased yields in each of the five growing seasons, 1992–96. Weather, N fertilizer and weed control appeared to explain much of the yield and grain quality variation. Soil P and K levels were maintained or increased by manure use. Plant foliar analysis indicated that soil macronutrients were mostly in the sufficient range for both management systems. Economic return in excess of the additional cost of the fertilizer and herbicides averaged $172.63 ha−1 for soybean, $165.63 ha−1 for corn and minus $19.19 ha−1 for wheat over the five-year study. Fertilizer and herbicides did pay with corn and soybean, but not with wheat under the conditions of this study.