Cultivation of high efficacious crops in resource utilization, especially with higher water and radiation use efficiencies is one of the important strategies to achieve the goals of sustainable agriculture. In agreement with these guidelines and in order to estimate light extinction coefficient and radiation use efficiency of sesame as a high value medicinal plant in arid regions a randomized complete block design with three replications was conducted in 2009-10 growing season. Treatments were three different types of biofertilizers plus control, including 1-nitroxin (containing of Azotobacter sp. &Azospirillum sp.), 2- biophosphor (PSB, containing of phosphate solubilizing bacteria, Bacillus sp. & Pseudomonas sp.), 3- biosulfur (SSB, containing of Thiobacillus ssp.) and 4- control (no fertilizer). The results showed that application of biofertilizers resulted to 15 days shorter period to achieve maximum leaf area index compared to control and as a result, the maximum fraction of absorbed radiation and consequently sesame dry matter produced at the sixtieth day after emergence, 15 day sooner than control. Although, light extinction coefficient in control (no biofertilizer) was higher than biofertilizer treatments (0.78 vs. 0.69), but radiation use efficiency (RUE) in SSB and nitroxinwas higher compared to control (1.31, 1.24 and 1.09respectively) which resulted to highest biological and seed yield, seed oil and protein and harvest index. In this research, the total mean sesame RUE estimated of 1.19 g MJ-1 (R2=0.95). In general, these results indicated that application of biofertilizers specially SSB and nitroxin enhanced utilization of radiated and absorbed radiation by sesame canopy and consequently improved quantitative and qualitative yields.

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