Evaluation of forage maize (Zea mays L.) yield in intercropping with pinto bean (Phaseolus vulgaris L.) under deficit irrigation and spermidine foliar application

Providing future food demand by providing a solution to achieve greater water use efficiency in the water shortage throughout the world, is a major priority in agriculture. Therefore, in arid and semi-arid countries, it is necessary to use methods to improve irrigation management in all maize planting systems. The use of intercropping systems in arid areas where water deficiency poses a serious threat to agricultural sustainability is an effective strategy to reduce the challenge of water scarcity. Deficit irrigation, which means reducing water consumption per unit area, is another way to manage irrigation. Another management strategy to improve production and increase plant tolerance to water scarcity is the use of polyamines as an external source that increases plant tolerance and growth. This study was performed to evaluate the yield of forage maize and pinto bean under deficit irrigation and spermidine foliar application treatments.

An experiment was conducted as split split plots based on a randomized complete block design with three replications. Main plots comprised three irrigation levels ((based on 60 (as control: NI), 80 and 100 mm cumulative evaporation from Class A evaporation pan as deficit irrigation (DI80 and DI100)), subplots included foliar and non-foliar spraying of spermidine and sub-sub-plots consisted five intercropping pattern (maize monoculture (Z), bean monoculture (F), intercropping of 50% maize: 50% bean, (Z %50: F %50), 80% maize: 60% bean (Z %80: F %60) and 80% maize: 40% bean (Z %80: F %40). It was carried out in the research farm of the Campus of Agriculture and Natural Resources of the University of Tehran in the 2009-2010 year.

the result showed that the experimental treatments was significant on maize Fresh and dry forage yield, bean grain and biological yield, bean and maize leaf area index. Due to the higher planting area in bean and maize monoculture treatments, the highest bean grain yield (2.62 t/ha) and fresh yield of maize (66.53 t/ha) were related to monoculture under normal irrigation and spraying treatments, Land Equivalent Ratio (LER) in all intercropping patterns was more than one, indicating their superiority over monoculture treatments that indicated higher ground productivity in intercropping pattern than in monoculture of crops all levels of irrigation. Deficit irrigation up to 80 mm, decreased maize Fresh and dry forage yield, bean grain and biological yield less than 10 percent and spermidine increased all traits values. The lowest bean grain yield (0.56 t/ha) and fresh yield of maize (29.92 t/ha) were obtained from 80%: 40% and 50%: 50% under the lowest irrigation rate and non-foliar spraying, respectively.

the result showed that intercropping pattern and spraying treatments is usefulness. Due to the slight decrease in forage maize yield in 80 mm evaporation and additive intercropping patterns (less than 6 and 20%, respectively, compared to monoculture under normal irrigation and non- foliar spraying), if the goal is to produce forage maize, deficit irrigation up to 80 mm evaporation from the pan and additive intercropping along with spermidine foliar application is recommended for maize and bean cultivation to increase the sustainability and forage production in karaj area.