A typical yield map from a Pennsylvania field. Courtesy G. Roth		(cost ~ $4000) that uses satellite signals to document precise positions on the ground, a producer can make a yield map showing the variability in a field's yield. Roth's crew has now made maps for about 300 fields on and around the College of Agricultural Science's Russel E. Larson Agricultural Research Center. Their conclusion is that yield mapping has the potential to identify problem areas in fields that may warrant more attention in sampling and scouting.      "The yield monitor really helps producers quantify the effects of various problems they encounter, such as poor weed control, low plant populations, or deer damage," notes Roth, "and this in turn provides them feed-back to adjust their management in the following year."      Dr. Doug Beegle, professor of agronomy, used GPS equipment to conduct soil nutrient mapping and found that Pennsylvania soils generally have high amounts of nutrients, but that soils even within one field tend to be highly variable. His work points to variability in soil physical properties such as soil depth, drainage, and texture as the main cause of variability seen in corn yields within Pennsylvania fields.
Yield Monitors continued from page 1 which was determined by using a weigh wagon. In field tests (3-10 acres), the accuracy of the yield monitor increased even further.       Roth's team developed the following recommendations to increase the accuracy of the yield monitor in Pennsylvania fields. Ideally, strips should be long and narrow, grain loads should be at least 2,000 pounds, grain moisture should be less than 25 percent, and the combine should be well calibrated.       Some growers in the Commonwealth are already using yield monitors to conduct strip tests of hybrids and monitor yields. The cost of this	precision equipment has so far limited the number of farmers able to purchase and use this technology. But Roth sees yield monitors as tools that are cost-effective in the long run. They will allow producers and researchers to make comparisons between the yields of various hybrids and other inputs. This will result in better on-farm decision making that can quickly recover the cost of the yield monitor.      The research team also wanted to know whether yield monitors provide useful data about the variability in yield throughout a field. A typical yield range might vary from 100 to 175 bushels per acre in a 10-20 acre field. By equipping a combine with a global positioning system (GIS) antenna	This research was done in support of the Agronomy Department's Cooperative Extension program. Members of the research team have presented this information at various extension conferences for crop consultants, producers, and county agents.       Besides Roth and Beegle, the team includes; Jeff Metz, farm machinery operator; Lynn Hoffman, senior research associate; Dr. Elwood Hatley, professor of agronomy; Dr. Dave Wagner, assistant professor of agricultural and biological engineering; and Mark Antle, research support technologist.      Greg Roth can be reached at (814) 863-1018 or gwr@psu.edu. This work was funded in part by a grant from the Pioneer Crop Management Research Awards Program and the Pennsylvania Department of Agriculture Research Program.