study effect of sowing ratios in marigold (calendula officinalis) and mungbean (vigna radiata) intercropping systems on weed control and mungbean yield improvement

introduction sustainability of agricultural systems may improve due to intercropping as a result of diversity increasing. marigold (calendula officinalis) is a major medicinal plant from asteraceae family, though weeds suppress it because of lower competitiveness against weeds. mungbean (vigna radiata) is a pulse crop from fabaceae family and is one of the major nutritive sources especially in developing countries. intercropping systems has a major role in suitable weeds control in crop fields. a primary and direct way of increasing diversity of an agro ecosystem is intercropping system that allows interaction between the individuals of the different crops and varieties. intercropping can add temporal diversity through the sequential planting of different crops during the same season. to optimize plant density, the sowing rate of each crop in the mixture is adjusted below its full rate. if full rates of each crop were planted, neither would yield well because of intense overcrowding. by reducing the sowing rates of each, the crops have a chance to yield well within the mixture. a research study was conducted by hunsigi & gupta (2010) revealed that intercropping of basil (ocimum basilicum) with mungbean in planting pattern of 25% basil and 100% mungbean lead to higher land equivalent ratio (ler). shahbazi and sarajuoghi (2012) reported that in multiple cropping of faba bean and maize crops with mixing rates of 75% maize and 25% faba bean yield and yield components of maize crop was the highest. this study has performed to evaluation intercropping effect of mungbean (vigna radiata) with two varieties of marigold kampar and porpar on yield and yield components of the both crops and weeds biomass. materials and methods a field study was conducted on marigold and mungbean in a split plot experiment based on randomized complete block design in three replications in islamic azad university, tabriz, north-west of iran, during 2014. the climate of research site is semi-arid cold with an average annual precipitation of 271 mm. the soil was sandy-loam with ec of 0.72 ds m-1 and ph of 7.8. the field was ploughed twice (october 2013 and march 2014) and fertilizers applied, based on soil analysis, were 80 kg ha-1 and 120 kg ha-1 of triple super phosphate and urea respectively. the field then harrowed to prepare the final seed bed. plots size was 3×4 m. treatments were marigold cultivars (kampar, porpar) and mungbean sowing rates (0, 12.5%, 25%, 37.5% and 50% of optimum density). an important tool for the study and evaluation of intercropping systems is the land equivalent ratio (ler). ler providing that all other things being equal measure of the yield advantage obtained by growing two or more crops or varieties as an intercrop compared to growing the same crops or varieties as a collection of separate monocultures. ler thus allows us to go beyond a description of the pattern of diversity into an analysis of the advantages of intercropping. the ler is calculated using the below formula. ler=yci/yc + ymi/ym an ler value of 1.0, indicating no difference in yield between the intercrop and the collection of monocultures. any value greater than 1.0 indicates a yield advantage for intercrop. all data were statistically analyzed based on randomized complete block design, using mstat-c software. the means of the treatments were compared using the duncan’s multiple range test at * p < 0.05. results and discussion dominant weeds emerged in the experiment field were broad leaves weeds such as lambsquarters (chenopodium album), redroot pigweed (amaranthus retroflexus) and small bindweed (convolvulus arvensis) and narrow leaves weeds bermuda grass (cynodon dactylon) and wild rye (secale montaneum). such as based on variance analysis, effect of marigold variety on its stem height and weeds biomass was significant. sowing rates influenced weeds biomass and dry flower yield of marigold. also, interaction of studied factors on grain number per pod and land equivalent ratio was significant. results showed that in marigold cv. porpar plots weeds had higher biomass than kampar. when mungbean was sown with 37.5% of optimum density, marigold dry flower yield increased significantly. greater flower yield was produced from marigold sole cropping and its intercropping with mungbean at 37.5% of optimum density, which were 103.5 and 95.8 g m-2, respectively. in planting patterns of 25% mungbean+100% marigold, 37.5% mungbean+100% marigold and 50% mungbean+100% marigold mungbean grain yields were higher (37.2, 39.9 and 41.6 g m-2 respectively). in all treatments except 12.5% mungbean+100% marigold land equivalent ratio was higher than unit. conclusion because of improvement of land equivalent ratio in marigold cv. kampar intercropped with different densities of mungbean and also in marigold cv. porpar intercropped with ˃25% optimum densities of mungbean plots, intercropping of 12.5% mungbean+100% marigold cv. kampar and 25% mungbean+100% marigold in cv. porpar could be recommended.