Response of faba bean and pea yield and yield components to cereal-legume intercropping under weed competitions

Introduction Cereal-legume intercropping is one of the best ways to increase the yield per unit area (to decrease the detrimental effect caused by weeds and to reduce application of fertilizers and herbicides. Stoltz et al. (2014) in a study on corn-pea intercropping reported that crops yield in intercropped plots was significantly greater than that of monoculture. It has been reported that barley-faba bean intercropping led to an increase in total grain yield and it could cause a decrease in weed biomass. Considering 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 faba bean and pea in intercropping with wheat, barley and triticale under weedy conditions in southern Fars Province. Materials & Methods A field experiment was performed in the College of Agriculture and Natural Resources of Darab, Shiraz University during 2014-2015. Treatments included 10 monoculture (wheat, barley, triticale, pea and faba bean with and without weeds) and 6 intercropping (wheat + pea, wheat + faba bean, barley + pea, barley + faba bean, triticale + pea and triticale + faba bean with weeds) which laid out based on a randomized complete block design (RCBD) with three replications. Irrigation intervals were 8 and 12 days based on environmental conditions. Weeds were hand weeded twice, at tillering and booting stages of cereals. After crop maturity, plants were hand harvested to measure yield and yield components. Additionally, partial land equivalent ratio (LER) was calculated. The partial land equivalent ratio has been defined as a measure of efficiency of an intercrop or mixture. The LER compares land areas required under single or sole cropping to give the yields obtained from the component crops of the mixture. Values greater than 0.5 indicate intercropping to be more efficient than sole cropping in terms of land use, while values less than 0.5 indicate a loss in efficiency due to intercropping. Values equal to 0.5 indicate that the components fully share the same limiting resource. The data analyzed by using MSTATC ver2.10 software (1991). Since the number of the plants was not similar in all the plots, the data was subjected to analysis of covariance. Results & Discussion Results showed a significant effect of treatments on 1000-seed weight of pea, number of pod per m2, number of seed per pod, grain yield, biological yield, harvest index and LER. The greatest 1000-seed weight of pea, number of pod per m2, seed yield and harvest index obtained in intercropping of wheat + pea (366.7 g), weed-free pea monoculture (1317), weed-free faba bean monoculture (4149 kg/ha) and weed-free faba bean monoculture (46.46 %), respectively. The highest number of seed per pod was obtained in intercropping of barley + faba bean (3.7), weed-free faba bean monoculture (3.29) and intercropping of wheat + faba bean (2.93), respectively. Total and partial LER of legumes in all intercropping treatments compared to weedy monoculture was greater than 1 and 0.5, respectively. The results showed that weed-free monoculture treatments had the highest grain yield, biological yield and harvest index. However, crop yield and harvest index in intercropping treatments were similar or superior to weedy monocultures. For instance, grain yield and harvest index in intercropping of wheat + faba bean was higher than those of in weedy faba bean monoculture, 102 and 93 %, respectively. In general, grain yield, biological yield and harvest index of pea and faba bean in weed-free monocultures treatments was higher than weedy monocultures and intercropping treatments. Grain yield and harvest index of intercropping was similar or higher than those of weedy monocultures. Conclusion Total and partial LER of legumes in all intercropping treatments compared to weedy monoculture was greater than 1 and 0.5, respectively. Since cereals are more competitive than legumes, it seems for increasing the efficiency of intercropping; a higher density of legumes should be used. Additionally, for reducing weed interference and increasing yield in pea and faba bean, the use of cereal-legume intercropping is recommended.