i) the number of replicates per experimental line was varied; (ii) the total number of experimental lines evalu-Breeders need information on the best way to allocate resources ated was varied and the number of yield plots was held to develop higher-yielding soybean [Glycine max (L.) Merr.] lines using a fixed amount of resources. Our objectives were to determine constant; and (iii) the number of populations used to the best resource allocation for first-year yield tests by varying the develop experimental lines was varied. number of replicates, number of lines per population, and number of populations. Thirty lines developed from each of 10 populations MATERIALS AND METHODS were tested in two selection environments. All 300 lines were evaluated in each of the seven environments. Five environments were used Ten soybean populations were evaluated. Each of the 10 as validation environments to compare the mean of the selected lines populations comprised 30 experimental lines that had been to the overall mean. Increasing the number of replicates did not inpreviously selected. Lines were selected as plant rows, on the crease the effectiveness of selection. When 30 lines were tested from basis of early maturity and visual appearance. The 30 selected five populations, the realized selection differential varied from 170 lines from each of the 10 populations were then evaluated in to 310 kg ha Ϫ1 , depending on which of the five populations werereplicated yield trials at each of seven environments. Soil type evaluated. We concluded that no more than 15 lines should be sampled and precipitation from 1 May to 30 September were deterfrom as many different populations as possible. The best allocation mined for each of the seven environments (Table 1). of resources to maximize the response to selection for first-year yield