Effect of late season drought stress and different combination of intercropping with barley on yield and yield components of chickpea and faba bean

A growing interest in intercropping systems has been initiated in developed countries due to the increasing awareness of environmental degradation arising from the heavy use of non-renewable resources such as water. Cereal-legume intercropping are common in natural ecosystems, but now are rarely used in developed countries, except for certain intercropping systems used for animal feed. A renewed interest in intercropping and particularly in intercropping of cereals with legumes has risen again lately. Intercropping can use the available environmental resources more efficiently and thus result in higher yields than monocropping. The reasons for the higher yield in such systems is that the intercropped species do not compete for exactly the same growth resource niche and thereby tend to use the available resources in a complementary way. Izaurralde et al, (1990) used chickpea intercropped with barley in different planting densities and found that grain, straw, and dry matter yields of the mixtures increased with increasing chickpea planting density. With respect to drought stress in late season of Sothern Iran because of cutting off rainfall in this area, and the importance of intercropping to reach stability and sustainability in production, the aim of this study was to assess the changes in yield and yield components of chickpea and faba bean intercropped with barley under late season drought stress. To evaluate the yield and yield components of intercropping chickpea and faba bean with barley cultivars under different irrigation regimes, a field experiment was conducted at College of Agriculture and Natural Resources of Darab, Shiraz University during 2014 growing season. Treatments were included two levels of irrigation regimes (full irrigation and cutting off irrigation at milk development of barley) and 8 cropping treatments consisted of monoculture of Nimroz tow-rowed barley, Zehak six-rowed barley, pea and faba bean and intercropping of Nimroz+pea, Nimroz+faba bean, Zehak+pea and Zehak+faba bean with a ratio of 1:1 which laid out as split plot arrangement in randomized complete block design with three replicates. At crop maturity, plants were hand harvested to measure yield and biological yield and yield components including number of pods/plant, number of seed/plant, and 100-kernel weight. Also, land equivalent ratio (LER) was calculated. LER is the most popular index for expressing the yield advantage of intercropping systems and defined as the relative land area that is required for monocrops to produce the same yields as intercrops. Finally, analysis of variance (ANOWA) was performed using MSTATC ver. 2.1 software (1991) and the means compared by LSD test at 5% probability level. Analysis of variance showed that main effects of irrigation regime and cropping treatments had significant effect on number of pods/plant in chickpea while these treatments had no significant effect on number of pods/plant of faba bean. Under drought stress, number of seeds/plant, 100-kernel weight, grain yield of pea decreased 40, 16, and 57% while in faba bean decreased 32, 18, and 40%, respectively. Interaction effect of irrigation regime and cropping treatment had significant effect on grain yield and harvest index of chickpea and faba bean while this interaction effect had no significant effect on biological yield of two legumes. In chickpea, the highest biological yield (9916 kg/ha) and grain yield (1630 kg/ha) were obtained in monoculture of chickpea and the highest 100-seed weight (25.5 g) and harvest index (%29.85) were obtained in Nimroz+pea intercropping. Also, in faba bean, the highest biological yield (11960 kg/ha) and grain yield (5175 kg/ha) were observed in monoculture of faba bean. Maximum harvest index (%45.58) was obtained in Zehak+faba bean intercropping. Interaction effect of irrigation regime and cropping treatment had significant effect on LERlegumes and LERtotal. Under drought stress, LER in legumes in all of the intercropping treatments increased from 13 to 80%. Likewise, the highest LERcereals (0.57), LERlegumes (0.83), and LERtotal (1.4) was obtained in Zehak+pea intercropping. It is concluded that intercropping of six-rowed Zehak barley cultivar with pea was advantageous system of each legumes in monoculture especially under drought stress condition because of better land use efficiency than sole cropping and the other mixtures. This intercropping system can be adopted by farmers for maximization of yield especially under late season drought stress in Southern Iran.