Conventional agriculture has definite effects on the environment, but what are the consequences of transitioning from conventional farming systems to systems that are less dependent on synthetic fertilizers and pesticides.  Interesting questions that comes about upon comparing conventional vs. organic agriculture are 2 fold.  Are the environmental effects of pesticides and fertilizers great enough to warrant an alternative system and is organic agriculture sustainable enough to be considered an alternative to conventional agriculture?

    Soil fertility and weed management have been identified as the most important factors limiting yields in the organic and low-input systems. In a study conducted at the University of California, project managers have altered production practices to address these constraints.  Organic and low-input tomatoes, for example, are now transplanted, pre-grown before planted in the field, instead of directly seeded. This practice leaves more time for cover crop growth, gives tomatoes a head start in competing against weeds and allows for the use of efficient mechanical cultivation techniques. Manure fertilizers and foliar sprays have also improved yields in the organic systems. Nonetheless, it has been difficult to obtain the high quality transplants necessary for optimal growth and yield. In the 1994 growing season, for example, researchers found that transplants in the organic and low-input systems were infected with a virus. Symptoms became apparent four to six weeks after transplanting, and yields in the organic and low-input systems were lower than in the conventional systems.

    Nitrogen availability appears to be an important factor determining tomato yields during the transition to organic production. Prior to 1992, tomato plants in the organic system were stunted and yellow early in the season, did not compete well with weeds, and had yields lower than tomatoes grown under conventional methods. These results were despite the fact that soil nitrate levels in the organic tomatoes in 1990 and 1991 were actually higher than or equivalent to levels in the conventional system. The reason for this phenomenon is probably related to the importance of microbial activity in an organic system. Unlike the conventional system where plants obtain nutrients from highly soluble chemical sources, the organic and low-input systems rely on microorganisms to make nutrients available for plant uptake.

(1)  A comparison of conventional, low-input and organic farming systems