Evaluation of yield indices and LER of different types of bean affected by row intercropping with cucumber

It has been predicted that the population of the world will reach up to 9 billion people until middle of current century so to meet the demands for food, it is necessary to supply more by developing sustainable agriculture and ecological intensification of food production to avoid disadvantages of conventional agriculture. Intercropping is one of the sustainable agriculture strategies that has been proven that causes more use of available resources by intercropped species. It is one of the key strategies of sustainable agriculture because of its efficiency in using of the resources like nitrogen, light and water and improving vulnerability of crops against diseases and pests. Pulses are very valuable for agroecosystems and human health, because of many advantages like high protein content and nutritional values and symbiotic fixation of nitrogen. So, an experiment was conducted in order to study of yield characteristics of black-eyed pea (BEP), the pinto bean (PB), kidney bean (KB) and green bean (GB) as bean ecotypes affected by intercropping with cucumber and partial land equivalent ratio (LER) of the beans.

The experiment was held during growing season 2015-16 in the experimental field of Ferdowsi University of Mashhad based on a randomized complete block design (RCBD) with six and eight treatments (for different studied indices) and three replications. Treatments included sole culture of BEP, PB, KB and GB and their 1:1 ratio in replacement intercropping with cucumber. The plots had five 120-cm sized width and 6×3 meter dimensions. The gaps between the plots and the blocks were one and two meters, respectively. The studied indices included the number of sub-branches per plant, stem length, number and weight of seeds per pod, numbers and weights of pods and seeds per plant, shrub and plant [dry] weights, 100-seed weight, biological and economic yields and harvest index for seeds of grain bean ecotypes (including BEP, PB and KB), and for GB, studied indices included the number of seeds per plant, 100-seed weight and economic yield (total weight of harvested green pods per ha). Partial LER of the studied plants was calculated and finally statistical analysis of data and drawing the figures done using SAS v.9.2 and MS Excel 2016 respectively. Duncan’s multiple range test (DMRT) also used for comparing the means at probability level of %5.

The results showed that except the number of sub-branches per plant, there were significant differences between the treatments for all other studied indices. The highest stem length was recorded in sole culture of BEP that was significantly different compared with other treatments but there was no significant difference between sole culture and intercropping treatments of PB and KB. Competition for interception of light may cause this result for BEP. Number and weight of seeds per pod and numbers and weights of pods and seeds per plant were higher in intercropping treatments of the plants in comparison of their sole culture. Many other studies like results of Noorbakhsh et al, (2015) and Khalaf (2016) support our findings. 100-seed weight was different between the plants but no significant difference was observed between intercropping and sole culture of each plant. It seems that 100-seed weight is a genetic property that not be affected by intercropping. The biological and economic yield of the bean ecotypes were significantly higher in their sole culture compared with their intercropping due to lower plant density in intercropping but by considering the results of partial LER calculation, it concludes that intercropping was more useful for all studied plants. The highest value of partial LER (0.69) was calculated in GB and the lowest one was recorded to KB. The economic part of GB was its green pods, so its partial LER was higher than another studied plants in comparison of other plants that their seeds form their economic yield. Similar to 100-seed weight, the harvest index was statistically different between the bean ecotypes but it was similar between sole culture and intercropping treatments of each plant because of parallel trends of variations of biological and economic yields of the plants.

Based on the results, intercropping of BEP, PB, KB and GB with cucumber is benefit for ecological intensification of production of the studied pulses. So, it can be suggested as an efficient strategy for sustainable development of food production.