PARENT SESSION
Symposium #1: Ecology and agriculture.
Sponsored by ESA Agroecology section
Organized by: D. Andow, S. Gliessman, N. Jordan, M. Liebman, B. Maxwell, D. Neher, I. Perfecto, A. Power.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Lecture Hall

Weeds in agriculture: How do they reduce the quantity and the quality of yield?

Bazzaz, F.¹, ¹

ABSTRACT- Weeds can compete with a crop for resources and reduce their yield. This situation is well known to weed scientists and is the basis for weed eradication. Millions of dollars are spent every year on this issue. Little is known, however, about the change in yield or about changes in the quality of the yield. We now know that various weed species have differing impacts on crops because they take up resources in differing quantities and deploy them in a variety of ways. This differential uptake and deployment impacts the quantity. However, little attention has been given to the impact on the quality of the product. In future climates with the expectation that CO₂ and temperature will rise, this change in the quality of the yield may have great impact upon feeding the billions of people. We grew wheat in ambient and double CO2 environments and found that wheat grown in elevated CO₂ had a lower N/C ratio. Tests by the USDA lab showed that this wheat is not suitable for bread making. Furthermore, models predict that there will be an increase in agricultural production (~15%) in the developed countries but a decline in agricultural production in developing countries. As these countries do not have the money to purchase the needed fertilizers and biocides. If this happens, the difference between developed and developing countries will be larger than it is today. This may lead to political instability and unrest. It is urgent that these critical issues be addressed by agricultural scientists.

KEY WORDS: weeds, climate change, CO2