A case study in eastern Virginia provides evidence that both environmental and farm profit goals may be satisfied by alternative nitrogen (N) management strategies for grain production. We used a linear programming framework with an N mass balance model to calculate returns from several options for providing N to crops. Replacing single applications of inorganic N fertilizer with split applications or with additions of organic N were found to reduce the potential for N loss from cropland and to increase net returns. For some N management strategiesy however, adoption may require financial and educational assistance. As a result, water quality policies may benefit by including such incentives.

In arid areas of western Rajasthan, major constraints responsible for low plant production include low and erratic rainfall, high evaporation, and low soil fertility, particularly with respect to organic carbon and nitrogen. These problems lead to acute shortages of grain, fodder and fuelwood. Sustainable crop and biomass production can be achieved through adoption of agroforestry, silvipastoral and agrihorticultural systems. Integrated nutrient and moisture management practices can help in controlling pathogens and in improving the soil environment for higher sustained production.

Crops grown in narrow rows (NR, 0.25 to 0.38 m) shade weed seedlings more than do those grown in traditional wide rows (WR, 0.76 m). NR crops may require less herbicide and interrow cultivation than WR crops for equally effective weed control. This hypothesis was tested by comparing weed control and crop yield in NR and WR crops when the following percentages of recommended application rates (RAR) of standard herbicides were applied: soybean, 0, 50 and 100%; sunflower, 0, 25, 50, and 100%; and corn, 0, 33, and 100% in three separate sets of experiments conducted over 2, 3, and 4 years, respectively. In all treatments with 100% RAR, excellent weed control prevented reductions in crop yield. When only 25 to 50% RAR was applied, weed control was consistently high in NR (82 to 99% control), but variable in WR (42 to 99% control). Weed control and crop yields typically were lowest in NR without herbicides. Interrow cultivation controlled 0 to 81% of weeds in WR crops. In reduced herbicide treatments (25 to 50% RAR), yields of NR soybean and sunflower typically were about equal to those in WR with 100% RAR, but NR corn yields were about 10% less. Considering the reduced herbicide use and lower weed control costs, planting corn, soybean, and sunflower in narrow rows may represent a practical form of low-input production of these important crops.

Genetic improvements in crop tolerance to diseases, insects, and other stresses have reduced or eliminated applications of pesticides and other inputs for many crops. However, little work has been done to examine the potential for increasing levels of tolerance to weeds, even though herbicides account for 69% of the pesticides used in the United States eachyear. This paper documents thatfor all 21 crops examined, varieties differ in their tolerance of non-parasitic weeds. Characteristics influencing varietal tolerance to weeds are summarized.

Agricultural research conducted in the United States since establishment of the U.S. Dept. of Agriculture and Land-Grant University System in 1862 has shown that regular and proper additions of organic materials are very important for maintaining the tilth, fertility, and productivity of agricultural soils, protecting them from wind and water erosion, and preventing nutrient losses by runoff and leaching. Several millennia earlier, Roman agriculturists were advocating crop rotations, green manuring, composts, legumes, farmyard manures, crop residues, wood ashes, seaweed, and sewage wastes for supplying humus and nutrients to restore or enhance soil productivity. Even earlier, Asian farmers also used these practices to maintain healthy and productive soils. Today the most serious problem in U.S. agriculture and agriculture worldwide is the widespread degradation of agricultural soils through erosion and the consequential decline in productivity. In view of how much information is available on the benefits of organic recycling on agricultural lands, one wonders why we aren't doing a better job of protecting and conserving our land resource base. We discuss strategies for using organic resources more effectively to achieve a more sustainable agriculture for the future.

The increased effort by Congress to reduce agriculture's adverse consequences on the environment has been focused almost entirely on changing agricultural production practices at the farm level Because the agricultural sector is highly integrated, attempts to change a specific industry within the sector, such as production, input supply, or processing, may have undesirable effects. Programs designed to achieve society's environmental objectives by forcing change in agricultural production practices will lead to increased frustration, new programs and regulations, and further conflict between society and farmers. To guarantee sustainability of U.S. agriculture into the next century, efforts to incorporate new social needs into production agriculture should include changes in the research agendas of public and private institutions, marketing grades and standards, and the institutions that support the agricultural producer.