The water extracts of allelopathic crops have potential to stimulate the plant growth when applied at low concentration. Most of the previous studies have evaluated the role of exogenous application of allelopathic water extracts at low fertilizer inputs. In this 2-year study, comprised of three independent field experiments, we evaluated the role of exogenous application of allelopathic water extracts of sorghum/sunflower and benzyl aminopurine, applied alone or in combination, in improving the productivity and profitability of bread wheat grown at optimum and high levels of inorganic fertilizers. In first two studies, the sorghum or the sunflower water extracts (5% each) and benzyl aminopurine were applied alone or in combination with benzyl amino purine under optimal (N:P = 125:90 kg ha−1) and high (N:P = 225:150 kg ha−1) fertilizer; no extract application and water spray were taken as control. In the third study, the sorghum water extracts and benzyl aminopurine were used alone or in combination, under optimal (N:P = 125:90 kg ha−1), high (N:P = 225:150 kg ha−1) and very high (N:P = 325:210 kg ha−1) fertilizer keeping water spray as control. The foliage sprays were done at 40 and 75 days after sowing in all experiments. The results indicated that stay green character, grain yield and yield components, and the profitability of wheat were improved with the exogenous application of sorghum/sunflower water extracts and benzyl aminopurine as compared with the control treatments in all experiments. This improvement can be attributed to enhanced physiological functioning and hermetic response of the crop plants to potential allelochemicals present in crop water extracts. The combine application of water extracts and benzyl aminopurine was most useful in terms of yield increment regardless of any fertility status, possibly due to synergistic action of the allelochemicals and the commercial growth regulator. In nutshell, combine use of allelopathic crop water extracts and benzyl aminopurine can be used to improve wheat yield under any fertility status. However, the application of allelopathic crop water extracts and benzyl aminopurine, either alone or in combination was not profitable when applied at high or very high fertilizer level.
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