عنوان مقاله [English]
One of the ecological strategies for increasing of stability is diversity creation by multiple cropping. So, intercropping is an advantage approach for utilization from environmental resource in comparison with monoculture. Intercropping, which is defined as growing two or more species simultaneously in the same field during a growing season, has been considered as an important strategy to develop sustainable production systems, particularly those which aim to limit external inputs such as chemical fertilizer and herbicide. Intercropping is a sustainable cropping practice that has been successfully implemented in agroecosystems. In 79% of biodiversity experiments, biomass production in species diverse systems was on average, 1.7 times higher than in monoculture. Biodiversity enhancement can increase productivity and other ecosystem functions through replacement and complementarity effects. Complementarity effects occur when intercropped plants with complementary traits interact positively to increase productivity, and here genuine yield gains are possible. Thus, it was aimed to evaluate the agrophysiological traits, and yield of canola intercropped with chickpea in different plant densities.
Materials and methods:
Ecophysiological aspects of chickpea-canola intercropping were assessed at the Agricultural Research Station, Faculty of Agriculture (latitude 35◦34'N, longitude 50◦57'E), University of Tehran, during 2014 growing season. The area lies at an altitude of 2010 m.a.s.l. The mean annual rainfall was 256 mm. The mean maximum and minimum temperatures were 27.5°C and 8°C, correspondingly. The soil type of the experimental site was clay loam with pH of 7.78. Irrigation of the entire experiment was done with an overhead sprinkler system on a weekly basis until soil had reached field capacity. Experiment was done as factorial layout bases on a randomized complete block design with three replications and eight treatments. Treatments were sole cropping of rapeseed (60 and 80 plants m-2; 60R and 80R), sole cropping of chickpea (30 and 40 plants m-2; 30C and 40C) and additive intercropping based on combination of the two species (30C+60R, 30C+80R, 40C+60R, 40C+80R). The crops' seeds were sown simultaneously. Leaf chlorophyll reading was measured in the youngest expanded leafs using an SPAD-502 (Minolta). The Photosynthetic CO2 assimilation was measured with a portable leaf chamber and an open-system infrared gas analyzer (IRGA). At the final harvest, plants were cut at ground level and seeds were separated by manual threshing. Grain productivity was used to calculate land equivalent ratio (LER). LER was calculated to measure efficiency of intercropping compared to pure cropping (Banik et al., 2006). SAS vs. 9.1 procedures and programs were used for analysis of variance (ANOVA) calculations. Least significant differences (LSD) test was use for means comparison at 5% probability level.
Results and discussion:
Results indicated that chlorophyll reading and protein percentage for canola in intercropping treatment with chickpea were more than its sole cropping. However, photosynthetic rate for both species in sole cropping was more than intercropping. The highest canola grain yield (370.7 g m-2) was achieved at sole cropping with 80 plants m-2 but this treatment had not significant difference with canola sole cropping with 60 plants m-2. Also, chickpea sole cropping in comparison with intercropping treatments had higher grain yield. Although, grain yields of canola and chickpea at sole cropping treatments decreased in comparison with intercropping, but evaluation of land equivalent ratio (LER) confirmed higher advantage of intercropping. At all of the intercropping treatments, LER was higher than one and the highest value for LER (1.46) was revealed at ‘30 plants m-2 chickpea+60 plants m-2 canola’ treatment. In fact, when the value of land equivalent ratio is less than 1, the intercropping affects the growth negatively and yield of crops grown in mixtures but when the value of LER is more than 1, the intercropping favors the growth and yield of the crops. Moreover, the total land equivalent ratio was higher in intercropping system compared to the sole cropping system, indicating the advantage of intercropping over sole cropping in utilizing environmental resources for crop growth.
Conclusion; In general, chickpea/canola intercropping had relative advantage in comparison with sole cropping and increased land use efficiency. So that, results indicated that intercropping of medium density of chickpea (30 plants m-2) with medium density of canola (60 plants m-2) may give better overall yield and income than sole cropping of canola and chickpea.
We would like to thank the funding from Faculty of Agriculture, Tehran University, Iran.