ConclusionsFrom the above it can be concluded that there are opportunities for improving the productivity of cowpea/maize in the southeast of Iran at the arid ecological zone. Intercropping is the best cropping system, because at this system light interception, soil moisture, soil temperature and yield were higher compared to sole crops. Microclimatic variation in intercropping system have caused favorable environmental conditions, ready for growth and high yield compared to sole crops. The cowpea-maize intercropping exploited more stored water than a sole maize crop; the beneficial effects of the intercropping (reduced evaporation and crop transpiration) appeared to greatly compensate the interception and uptake losses near the cowpea canopy. It is evident from the results, that cowpea and cowpea-maize intercropping are more effective in improving soil water retention compared to sole maize. Thus 100% maize + 100% cowpea planting ratio had the highest LER at two years, and additive design absorbed higher PAR than replacement design. Evaporation from the soil surface decreased due to shading in this treatment (100% maize + 100% cowpea) and increased the amount of water potentially available for transpiration and growth.