Study the effect of soil dust on the competitiveness between bean (Phaseolud vulgaris cv. Kosha) and Chenolodium album (L.) and Echinochloa cruss-galli (L.) P. Beauv.

Dust is an atmospheric pollutant that is considered as one of the major environmental problems all over the world. This phenomenon is problematic, especially in agriculture, health, and transportation sections. Dust causes considerable environmental problems for agriculture and human health in Iran every year and so attention must be paid to the negative consequences of this phenomenon. Therefore, this study was conducted to quantify the effects of dust on growth and yield of red bean, weeds growth, and the competitive balance between weeds and the crop.

A greenhouse experiment was conducted in a replacement series based on a complete randomized design with three replicates in Ilam University, Ilam, from late October 2017 to early March 2018. The treatments consisted of soil dust (with and without), two weed species (Echinochloa crus-galli and Chenopodium album), and mixtures of 100% crop, 75% crop+25% weed, 50% crop+50% weed, 25% crop+75%weed, and 100% weed. The speed of photosynthesis, amount of chlorophyll α, chlorophyll b, total chlorophyll and carotenoids content of leaves, number of pod per plant, one thousand seed weight, and crop seed yield, crop and weed biomass were measured.

The results showed that the speed of photosynthesis amount of chlorophyll α, chlorophyll b, total chlorophyll content of leaves, carotenoids, number of pod per plant, one thousand seed weight, biomass, and seed yield of the red bean as well as biomass of weeds were significantly affected by dust. In addition, the effect of weeds on crops was increased by an increase in the weed proportion in the mixtures, which was worsening by the dust. The dust caused a 39.7% reduction in the yield and 52.8% in biomass of bean on average. The bean yield (gr/plant) in the 50% mixture in competition with C. album with and without dust effect were 7.5 and 4.7 gr/plant, respectively, while the corresponding values for E. crus-galli were 16.9 and 8.4 gr/plant , respectively. On the other hand, E. crus-galli as a narrow leave species was less affected by dust than C. album as a broad leave species and thus biomass reduction due to dust in C. album and E. crus-galli were 10.6% and 7.1% in comparison with the control , respectively. Moreover, the red bean was affected by dust more than weeds.

The growth and yield of red bean were significantly affected by competition with weeds and also the competitive effect of C. album was more than E. crus-galli. In addition, the dust had significant effects on the growth of red bean and weeds (C. album more than E. crus-galli). This might be due to the morphological characteristics of each species, because the broader leaves of the red bean and C. album may have caused more absorption of dust particles. In general, the dust phenomenon caused a reduction in crop growth and yield and also affected the competitive balance between weeds and crops.