Abundance of insects in sole culture and intercropping system of soybean (Glycine max) and corn (Zea mays)

Increasing the production of products with greater diversity through mixed cultivation can be effective in improving ecosystem services and functions. One of the most important functions of the mixed crop system is the reduction in the population of pests and, consequently, the increase of crop yields. This research is aimed at effects of the intercropping system of soybean and corn on abundance of insect pests, pollinators and natural enemies, an experiment was conducted at the Agricultural Research field of Lorestan University, Iran. The experiment was carried out in the randomized complete block design on five treatments with four replications. The experimental treatments were sole soybean 100:0, sole corn 0:100 and 50:50, 75:25 and 25:75 soybean: corn combinations, respectively. Different sampling methods such as pit fall trap, sieve, yellow and blue sticky cards, striking, sweep netting and local counting were applied to collect insects. Sampling was taken five times at interval of 14 days. Total of 7,395 insects were collected during the sampling period belonging to 10 orders and 39 families. Results showed that the population of the collected insect including pests, pollinators and natural enemies were significantly influenced by the intercropping system. The maximum number of natural enemies and the minimum number of pests were also observed in the 50:50 soybean: corn treatment. The maximum number of pollinating insects was found in 75:25 soybean: corn treatment. However, the highest rate of pests and subsequently the lowest pollinating and natural enemy insects were found in the sole corn treatment. On the other hand, a negative relationship between natural enemies and pests as well as soybean yield and pest insects was obtained. The population of some pest families influenced by the system showed an increase in abundance of insects in intercropping system compared to that of the control treatment (i.e., sole cropping). Results showed that, some mixed treatments of soybean: corn proved to have more efficient biological control and more yielding than their sole cultures.