The Northwest Wheat Region is a contiguous belt of 3.3 million ha in Idaho, Oregon and Washington. Its climate varies from subhumid (<650 mm annual precipitation) to semiarid (<350 mm), with more than 60% of the annual precipitation occurring during the winter. Winter wheat yields range from a high of 8 t/ha in the wetter zones to a low of 1.5 t/ha in the drier zones. Winter wheat is grown in rotation with spring cereals and pulses where annual precipitation exceeds 450 mm; winter wheat-fallow prevails where annual precipitation is less than 330 mm. Tillage practices are designed to maximize infiltration and retention of water through soil surface and crop residue management. Because of the combination of winter precipitation, steep topography, and winter wheat cropping, much of the region is subject to a severe water erosion hazard, accentuated by freeze-thaw cycles that increase surface runoff and weaken the soil structure. Wind erosion is a major problem in the drier zones, where cover is less and soils are higher in sand. Residue management, primarily through reduced tillage and no-till systems, is the first defense against both wind and water erosion, but yields often are higher with conventional intensive ti llage. Factors that limit yields with conservation farming include weed and disease problems and th e lack of suitable tillage and seeding equipment. Conservation strategies must shift from relying on traditional tillage methods to development of complete no-till systems. Spring cropping as a replacement for winter wheat also needs to be investigated. In some cases, tillage for water conservation must be made compatible with tillage for erosion control.

Sustainable crop production in the Pacific Northwest dry-farmed areas relies heavily on tillage and residue management systems to conserve water. Stable, sustainable yields cannot be achieved without adequate water conservation techniques. Frozen soil can reduce infiltration markedly, which decreases overwinter profile water storage and can cause severe soil erosion. Uncurbed evaporation losses throughout the year can greatly limit yields, particularly with summer fallow.

In both summer-fallowed and annually cropped regions where soil freezes frequently, fall tillage is used to increase surface macroporosity and to provide open channels to below the frost depth. This enhances infiltration throughout the winter and insures better water intake during rapid snowmelt and rainfall when the soil is frozen. Fall tillage enhances overwinter water recharge under these conditions, whereas in areas where soil freezes infrequently, it does not improve water storage efficiency.

In the dry-farmed regions receiving less than 330 mm annual precipitation, a winter wheat-fallow system is used to reduce the risk of uneconomical yields. Successful establishment of winter wheat following summer fallow is feasible only when proper management has suppressed evaporative loss. During the dry summer fallow, tillage is used to develop and maintain a soil mulch that restricts the flow of water, as both liquid and vapor. The tillage mulch effectively conserves stored soil water and maintains adequate seedzone moisture for fall establishment of winter wheat. However, the soil mulch can lead to high wind and water erosion.

In the Pacific Northwest dry-farmed region, tillage by itself is not considered a substitute for proper residue management. Crop residues following harvest are important for conserving water and controlling erosion. Under conservation programs implemented since 1985, shallow subsurface tillage systems that maintain residues on the surface have substantially reduced wind and water erosion in the region. Surface residues are effective in decreasing evaporative water loss and trapping snow during the winter, and therefore increase overwinter recharge. While surface residues are much less effective in suppressing evaporative losses in dry-farmed areas during extended dry periods, residues provide substantial control of wind and water erosion during the fallow.

Before conservation tillage systems came into use in the Pacific Northwest, water conservation frequently was achieved only through tillage. This helped to stabilize yields, but at a high cost to the soil resource. Poor use of surface residues and intensive tillage contributed to extensive wind and water erosion. Continued use of these practices would have caused yields to decline over time and required greater agrichemical inputs. To meet soil and water conservation needs, site-specific tillage and residue management systems were developed to account for the diversity and variability of soils and climate across the Pacific Northwest. Common to all these production systems is that both water conservation and effective residue management to protect the soil are required for long-term sustainable production.

With the passage of the 1990 Clean Air Act came the responsibility to monitor and control particulates in the size range 10 μ and smaller (PM10). Many urban areas, particularly in the western U.S., have experienced concentrations of fugitive dust particulates from upwind sources that exceed the federal health standards. Often a significant amount of this material is generated upwind on agricultural fields, and then is entrained and transported in the regional air mass, thus degrading the air quality in downwind urban regions. Current technology cannot adequately quantify the fugitive dust emitted and transported from agricultural sources, nor specify adequate control methods. A comprehensive research plan recently was developed and initia ted for the Columbia Plateau of eastern Washington State that involves multiple disciplines and several state and federal agencies. This research has several components: characterizing the soil, vegetation and climate in a region of 136,000 km2; developing wind erosion and fugitive dust emission relationships for individual farm fields; developing and applying transport-dispersion-deposition models of the region; selecting and testing farm-level control strategies; and providing public information to both the urban and farm communities for understanding the problem and developing management plans. Simultaneous receptor analyses and public health research combine to make this a comprehensive regional research effort on fugitive dust emissions and impacts.

Disease resistance, increased crop residues and altered plant and canopy design are the primary strategies being used to solve the major problems of cool season food legumes that are an integral component of cropping systems in the rainfed areas of the U.S. Pacific Northwest. Dry pea, seed pea and lentil predominate among these legumes, but there is increasing interest in chickpea. Several diseases are major hazards to production, including root rots, wilts, powdery mildew, Ascochyta blight, and viruses. Pea and lentil cultivan resistant to root rots, wilts, and powdery mildew are being developed and released. Progress is being made on resistance to v iruses transmitted by aphids, including pea enation mosaic and bean leaf roll. Development of res istant cultivars has been the principal control strategy for several diseases: Ascochyta blight of chickpea and lentil; root rots and wilts of pea, lentil, and chickpea; powdery mildew of pea; and viruses of pea and lentil. Chickpea cultivars resistant to Ascochyta blight were recently made avallable to producers. Another problem is that crop residues are insufficient to control erosion. Research is underway on genetically increasing biomass and residue production in lentil and dry pea and on producing more lignified stems and other plant parts that are more resistant to breakdown during harvesting and subsequent tillage. Increased biomass also might increase grain yields and red uce harvesting losses. The semi-leafless and woody stem traits in pea, the bushy plant types of lentil and chickpea, and diverse pod traits in all the legumes have shown promise for increased yield potential, ease of harvest, and reduced shattering losses.

Sustainable rainfed cropping systems are needed in the Pacific Northwest of the United States to reduce or eliminate wind and water erosion, improve soil quality, and control weeds with reduced chemical inputs. A grass seed cropping system is excellent for improving soil quality and for controlling erosion, and can be grazed by sheep to produce meat and wool Tilla ge and residue management methods that create a rough surface to reduce wind and water erosion and increase water infiltration include: use of a chisel to create large clods; leaving residue on the surface; and use of the Paratill to shatter the soil to increase water infiltration with little disturbance of the soil surface. Including a legume in the rotation may help to break disease cycles, add N and C to the soil, and improve soil biological properties. The use of surface residues and tillage to control erosion and increase water infiltration may demand new approaches to weed contro I Rhizobacteria that attack the roots of weeds but not of wheat may reduce the need for chemica I herbicides. Research being conducted on these techniques in the Pacific Northwest of the United States and in other countries should soon result in guidelines for sustainable agricultural systems for the dryland, rainfed areas of the world.

Tillage, seeding and fertilizing implements for rainfed cereal production with a winter precipitation pattern have unique functional requirements. In designing and developing implements for these systems, soil and water conservation principles are critical and must be integrated into the total production system. Plant diseases, insects, weeds, environmental degradation, crop yield, crop quality and economics all may be influenced by tillage, seeding and fe rtilizing implements. Advances have been made in implements f or improved residue management, stand establishment and crop fertilization that leave more crop residue on the surface for soil and water conservation. However, they alter the seed and root zones, often resulting in uncontrolled pests, reduced yields, or increased production costs. Research is needed to integrate production implements into ecosystem management through automatic control systems for improved tillage, se eding and fertilizing. These systems should include field history mapping, real-time soil sens ors, and models to link data bases with equipment functions.

Cultivars vary considerably in how they respond to moisture stress throughout crop development. In areas of the Pacific Northwest with less than 250 mm of annual rainfall, win ter wheat is under moisture stress most of the time from planting to harvest. Cultivars must be ab le to absorb moisture, germinate, and emerge under high temperature, poor seed zone moisture, and deep seed cover. Moisture stress slows emergence and seedling development and reduces most yield components, including number of tillers, seeds per spike, seeds per unit area, seed size, and seed weight per unit volume. Additionally, leaf senescence and maturity are earfy under moisture stress conditions. A cultivar cannot obtain its potential yield with less than adequate moisture; therefore, under moisture stress fewer tillers and seeds are produced. Which plant structures are reduced is determined by the growth stage of the plant during stress, while the extent of this reduction is determined by the severity of moisture stress and the genotype of the cultivar.

Diseases continue to be important constraints in wheat and barley conservation cropping systems in the semiarid Pacific Northwest. Several diseases are more damaging in highthan low-residue seedbeds, and in crops planted during early autumn to reduce soil erosion during winter, especially unirrigated winter wheat in rotation with summer fallow in low rainfall zones (250–400 mm). Changes in cropping systems in the region have made disease management and maintenance of yield goals and farm profitability more challenging because disease management often is more complex and expensive with conservation tillage than inversion tillage. Practices being developed to meet this challenge are reviewed for diseases that are particularly trouble some in conservation farming systems of the Pacific Northwest.

Six species of ophids (Homoptera: Aphididae) are the most economically significant insect pests of wheat in Washington. Management technologies under development or in use in Washington emphasize biorational approaches, including development and use of resistance germplasm, manipulation of pest populations through cropping systems, and development of biological controls. We review wheat yield losses caused by aphids, their biological control, and the effects of conservation tillage and systemic seed treatment.

The Pacific Northwest dryland region is moving toward conservation tillage to control excessive erosion on steep slopes, but progress has been slow because of adverse effects on plant growth and yield. Fertility relations in cereal grains with conventional tillage are well known, with deficiencies occurring for nitrogen, sulfur, and phosphorus, in declining order of frequency. N and S deficiencies are more severe in conservation tillage, although the pattern of crop response to nutrient application is the same as in conventional tillage. Placing nutrients in a subs urface band near the seed is more effective than broadcasting on the surface. Higher fertility is required near developing root systems to offset greater competition from grassy weeds and more intense pressure from root-pruning soil pathogens. Conservation tillage alters soil fertility and plant growth in different ways on different landscapes. These differences must be considered to ensure tha t conservation tillage will be effective over the entire field.

The long-term productivity, sustainability, and environmental impact of cropping systems cannot be assessed adequately using conventional agronomic experiments. This pap erdiscusses the use of computer-based technologies as support tools for this type of assessment, including crop growth simulation models, weather generators, geographical information systems, and risk assessment and economic models. Comprehensive systems that integrate these technologies are just emerging, offering great potential for the analysis of agricultural systems in the future.

The demand for more ecologically and economically sustainable agriculture arises because we currently integrate products economically in a fashion that distorts ecologica I relationships. Earfy farms were ecologically integrated through feeding of forage crops and crop residues to livestock, with livestock contributing draft power and manure for crops. Today we have almost entirely uncoupled plant and animal production, eliminating the contribution that each can make to the productivity of the other. Barriers to integrating farming systems include the large volume of information needed for sophisticated production systems and the lack of infrastructure. Also, many chemicals used on crops have not been evaluated for their safety in food animals. Winter feeding and calving may conflict with crop production cycles; balancing year-round forage supplies is another obstacle. Opportunities include using the Conservation Reserve Program to shift land to livestock production. Domestic demand for meat is changing, and range livestock production is seen by some people as more humane than confinement. Animals fed less grain may be more acceptable in some markets. As agriculture responds to changes in society, ecologica I integration may become more compatible with economic integration.

An evaluation of agricultural systems often involves multidisciplinary teams that include crop scientists, animal scientists, soil scientists, pest control specialists, agricultural economists, and others. Agricultural economists can improve the technical quality and comprehe nsiveness of agricultural systems research in six major areas: budgeting and investment analyses; whole-farm and institutional factors; risk considerations; aggregate effects on crop and livestock prices; society-wide welfare effects of technical or policy changes; and economic values of environmental and other nonmarket effects. Economic analysis has been part of several successful multidisciplinary research efforts in the United States Pacific Northwest. These have covered soil conservation, integrated pest management, sustainable agriculture, crop rotation choice, and beef ranch management. As an example of institutional influences on economic outcomes, one study showed that the structure and selectivity of United States commodity programs have favored conventional over low-input rotations. Regarding risk management, an appropriate “package system” including conservation tillage, a diversified crop rotation, and adequate chemical weed management was shown both to sustain profitability and to reduce income fluctuations. Properly designed economic analysis can make similar contributions to identifying successful dryl and agricultural technologies throughout the world.