In order to derive selected communities with high yield and water stress tolerance, the effect of selection on maize (Zea mays L.) yield and growth improvement was studied under some a biotic stresses (water, N and K) with four fertilizer combinations (K100 N250, K200 N250, K100 N500, and K500 N200). A field experiment was conducted during six seasons (2009-2011) in the field of Crop Science Dept.-College of Agriculture-University of Baghdad. In this experiment, the synthetic cultivar, Ibaa 5012 was used. The selection depended on grain yield under sufficient and insufficient water. The plants were selected from each group of combination according to phenotypic superiority, and undergone to self-pollination for three cycles under sufficient and non-sufficient water. In the fourth season, the manual random mating was used selected plants in each group, the resulted seeds from random mating were divided into two groups, which were planted in a comparative experiments for spring and fall seasons under irrigation levels(5 and 10 days), to compare them with the origin under tow plant densities (60 and 80 thousand plant/ha).The results showed the superiority of plants selected from 10 days irrigation .Ear length increased by20% and 40% for SDN2K2 in spring and fall season respectively .Ear number.plant-1 by 6% and 9% for SDN1K1 in spring and fall season respectively. Grain number .ear -1 increased by4% and 41% in spring and full seasons for SDN2K2 respectively. Grain yield Mg.H-1 increased by5%, 95% in full season. Selection cycles also affected the field characters of all selected plants under sufficient water (5 days) in the same way. Ear length increased by 25 and 24%) for SN1K1 and 40 and 34% for SN2K1 in both seasons respectively. Row.number.ear-1 increased for SN2K1 by 13% and 20% in spring and fall season respectively. Grain number.row-1 increased 20 and 9% and 25 and 24% for SN1K1and SN2K1 in spring and fall seasons respectively. Grain yield increased by 21 and 20% and 50 and 63% for SN1K1,SN2K1 in spring and fall seasons respectively. So we recommend the selection for high yield and device lines that tolerant to both of dry stress and high plant density to be used in breeding programs under a biotic stresses and producing improved cultivars that be suitable for these environments or to be crossed to produce elite hybrids.