Study of ecological aspects of Sesame (Sesamum indicum L.) and Mung Bean (Vigna radiata L.) intercropping in weed control

IntroductionWeed infestation causes an extremely reduction of crops yield. On the other hand, increasing the diversity of crops in agro-ecosystems will change the biomass distribution of weeds community, thereby reducing the number and density of different weed species. Weed management in the past few decades has been in conflict with ecological principles and sustainability of the production systems. As well as, it has changed from the one dimensional methods to integrated techniques based on the various non-chemical methods. Generally, weed management is possible through agronomical, mechanical and biological techniques in addition to chemical methods. One of these non-chemical methods is intercropping which has been used in farming systems since many years ago. The ability of intercropping systems to compete with weeds and proper control of weeds depends on various factors, including the composition of plants, varieties, density or proportion of intercropping and soil fertility. Besides, reduction of vacant niches and available resources for the growth of weeds are also reduce the ability of weeds invasion. So, the weed control in intercropping is much more effective than when the plants are planted alone. Majority of studies in recent years show that most of these researches have been performed in order to achieve maximum crops yield and its environmental effects is not considered. So, this research was aimed to investigate the effect of Sesame and Mung bean intercropping on yield, yield components, weed control, and determination of the best intercropping proportion in comparison with sole cropping in Mashhad, Iran.
Materials and MethodsThis research was carried out to investigate the ecological aspects of substitution intercropping of Sesame (Sesamum indicum L.) and Mung bean (Vignaradiata L.) in the presence and absence of weed control. The experiment was arranged as a split plot based on a randomized complete block design with three replications at research farm of faculty of agriculture, Ferdowsi University of Mashhad, Iran, during 2013 and 2014 growing seasons. The main plots included five treatments: sole Sesame, sole Mung bean, 3:1 intercropping (75% sesame-25% Mung bean), 1:1 intercropping (50% sesame-50% Mung bean), 1:3 intercropping (25% sesame-75% Mung bean), and sub plots were two levels of weed control (Weedy and weed-free). In order to implement an ecological and low input system, no chemicalinputs (fertilizers and pesticides) was applied. Weeds were harvested every 15 days corresponding to 4 harvests during the days after sowingand after separating were counted based on the type of species.
To determine the variation of weeds, Shannon index was used, according to below equation:H'=-Σni/N×Ln ni/N
H': Shannon index, ni: the number of the desired weed species and N: total number of weeds.
At the end of the growing season plant height,number of inflorescences per plant, number of grains per inflorescence and 1000 grain weight were determined for each plant. Grain yield, biological yield and harvest index were also calculated.
To compare the performance of intercropping treatments, land equivalent ratio (LER) was used, according to below equation:LER= Ʃ Ypi/Ymi
Ypi: yield of each plant in intercropping, Ymi: yield of each plant in sole cropping.
The data statistical analysis and draw the figures were performed by SAS, Version 9.1 and Excel. Means were also compared by Duncan’s multiple range test at the 5% probability level.
Results and DiscussionResults indicated that 3:1 intercropping treatment (75% sesame-25% Mung bean) had the lowest relative weed density. Shannon index was the lowest for 3:1 treatment (75% sesame-25% Mung bean). Plant height, number of inflorescence per plant, number of seeds per inflorescence, seed yield, biological yield, and harvest index represented a significant difference between weedy and weed-free treatments in both plants. Land equivalent ratio (LER) among the different patterns of intercropping showed that the amount of this ratio in weed-free treatments was greater than one, especially in comparison with weedy treatments. Results of the weedy treatments also showed that the amount of LER was only in 3:1 intercropping treatment (75% sesame-25% Mung bean) greater than one (1/04 in 2013 and 1/38 in 2014).
ConclusionTherefore, intercropping systems can be used as an ecological approach to reduce the use of herbicides in agriculture. It also can be as a suitable alternative to prevent the accumulation of chemical inputs in the environment.