The residual effects of historical broiler litter applications on soybean productivity is currently being evaluated. Between 1997 to 2002, annual broiler litter application treatments were: 0, 2.2, 4.5, 6.7, 9.0, 11.2, 13.4, and 15.7 Mg/ha.  In 2003, the broiler litter application was reduced to a half the above rate. In 2004, no broiler litter applications were made.  Throughout this period,  corn was grown on these plots with only broiler litter applications and no fertilizer.  During the 2005 and 2006 season, soybeans were grown on these historic plots with no further broiler litter applications. In these soybean experiments, extra phosphorus (258 kg/ha of P₂O₅) and potassium (280 kg/ha of K₂O) was applied to the low fertility plots that had received the historical low broiler litter rates (2.2 or 4.5 Mg/ha). In these two years, the soybeans receiving the extra supplemental phosphorus and potassium did not yield as well as the plots with historic high broiler litter rates.  Overall, the soybean yields were significantly higher in the plots with the high historic broiler litter application rates compared with plots that had received lower broiler litter rates.  In 2007, a soybean experiment has been conducted to investigate reasons for this effect. Because of the severe drought during 2007, the experiment was irrigated using drip lines.  At the R6 stage, the total above-ground portion of the plants  within a 0.5-meter of row was harvested and is being analyzed for 13 elements.  Additionally, soil fertility, soil quality, and soybean yields are being measured.