Allelochemicals may have concentration dependent influence on plant growth. At low concentration these chemicals promote the plant growth and may suppress the same when applied at higher concentration. This study was conducted to evaluate the growth promotery potential of sorghum, rice, maize and moringa water extracts. In the laboratory trials, application rate and frequency of sorghum, rice and maize water extracts (fresh and boiled) at different concentrations (100, 50, 25, 10, 5, and 3%) were evaluated and optimized for growth promotion of maize. Fresh and boiled extracts of sorghum, maize and rice were foliar applied alone and in combination with each other and along with moringa leaf extract (3%) at 30 and 50 days after sowing (DAS). Lower concentrations (3%) of sorghum, rice and maize plant water extracts promoted the seedling growth and seedling dry weights as compared to higher concentrations (25, 50 and 100%). In field experiments, combined application of fresh sorghum and moringa water extract (3%) increased the grain yield by 34-35% over control; whereas application of boiled plant extracts provided 35-38% improvement in grain yield over control from the combined application of boiled sorghum and maize water extracts at 3%. Moreover, marginal analysis of field experiments indicated that application of sorghum water extract (SWE) alone and combined application of rice and sorghum plant extracts had more marginal rate of return; nonetheless, application of fresh extracts had more marginal rate of return in this regard. In conclusion, application of allelopathic plant water extracts at lower concentrations (3%) alone and in combination improved the growth and productivity of maize. However, fresh water extracts alone or in combination may be preferred.