Evaluation of land productivity, competition and insect diversity in different intercropping patterns of sunflower (Helianthus annuus L.) and soybean (Glycine max L.) under low-input condition

Intercropping is a sustainable practice to achieve higher production with the aim to limit external inputs. A field experiment was conducted at the research farm of the Faculty of Agriculture, University of Maragheh, Maragheh, Iran, during 2016 growing seasons with ten treatments to evaluate the yield, analyze the competition and insect’s assemblages in sunflower (as main plant)/soybean (as companion plant) intercropping. Treatments included sunflower sole cropping, soybean sole cropping, replacing intercropping sunflower with soybean (50:50, 34:66, 66:34, 40:60, 60:40, 25:75) and additive intercropping of two plants (100:50 and 100:100%). Results showed that the highest sunflower grain yield (275 g m-2) was obtained in sunflower monoculture that was not significantly different with intercropping ratios of 25:75 and 60:40. Also, the highest and lowest grain yield of soybean was achieved in soybean monoculture (130.1 g m-2) and ratio of 100:50 (48.5 g m-2), respectively. The highest land equivalent ratio, monetary advantage index and intercropping advantage value was obtained in intercropping ratio of 25:75. Moreover, in all cropping patterns the aggressivity (A) and crowding ratio (CR) values of sunflower were higher than soybean, indicating that sunflower was the dominant species.  Also, the highest density for herbivores was recorded in soybean monoculture and the families of Thripidae (37.60- 43.87%) and Cicadellidae (34.01-37.71%) had the most relative density. Furthermore, intercropping of sunflower with soybean increased pollinators and natural enemies’ abundance compared with monocultures. Overall, based on the ecological, agronomical and economical indices intercropping sunflower with soybean with ratio of 25:75 is a feasible alternative method to achieve similar production with respect to monocropping.