Little information is available on the early effects of manure P from poultry [both chicken (Gallus gallus domesticus) and turkey (Melleagris gollopavo)] on corn (Zea mays L.) production. This study assessed the effects of poultry manure application rates commonly used by Corn Belt crop producers on corn early growth and early availability of P. Twelve trials were established across Iowa where three rates of P (0, 25, and 50 kg P ha-1) were superimposed on three poultry manure rates (from broilers, egg layers or turkeys) consisting of a non-manured control and two rates that varied between (low 21-63 kg total P ha-1 and high 50-123 kg total P ha-1). Treatments were replicated three times. The aboveground parts of corn plants and soil samples were collected at the V5 to V6 growth stage. Plant samples were dried, weighed, and analyzed for P concentration. Soil samples were analyzed for Bray-P1 (BP), Mehlich-3 (M3P), Olsen P (OP), and water-extractable P (WEP). Corn early growth and P uptake usually were increased by manure and fertilizer P, even in several sites with high initial soil P levels. Analysis of results at each site and for approximately similar rates of poultry manure and fertilizer P across sites provided no evidence that manure or fertilizer differed in increasing early growth or P uptake. Early plant growth and P uptake responses were poorly correlated with soil-test P (STP) measured at the V5-V6 growth stage. The soil tests did not detect a statistically significant soil P increase due to manure or fertilizer P application at some sites due to very high variability. The BP, M3P, and OP tests detected approximately similar manure and fertilizer P effects on STP. However, the WEP test detected manure P effects on soil P only in the few sites where there manure had highest percentage of water-soluble P. Overall, the study did not provide evidence for a difference between poultry manure and fertilizer P at increasing early corn growth and P uptake. Also, the study showed that the WEP soil P test was inferior to the routine P tests at assessing available poultry manure P for corn but could be more appropriate for assessing risk of dissolved P loss after manure application.