Document Type : Research Paper

Authors

• Asieh Siahmarguee ¹
• Benjamin Torabi ²
• Eid Mohammad Sohrabi Rad ³
• Syed majid Alimagham ⁴

¹ Assistant Professor, Department of Agronomy, Faculty of Crop Production, Gorgan University of Agricultural Sciences and Natural Recourses, Gorgan, Iran.

² Associated Professor, Department of Agronomy, Faculty of Crop Production, Gorgan University of Agricultural Sciences and Natural Recourses, Gorgan, Iran.

³ M.Sc. Student, Department of Agronomy, Faculty of Crop Production, Gorgan University of Agricultural Sciences and Natural Recourses, Gorgan, Iran.

⁴ Ph.D. Student, Department of Agronomy, Faculty of Crop Production, Gorgan University of Agricultural Sciences and Natural Recourses, Gorgan, Iran.

Abstract

To investigate the factors affecting soybean yield loss in comparison to the attainable yield, an experiment was conducted in 50 fields in the township of Kalaleh in summer of 2016. Sampling of weeds were taken in early growing season of soybean based on W pattern. In this study all agronomic management information including land area, farmers experience, seed bed preparation, sowing date, cultivar and provided seed source, sowing methods, seed rate, weeds control methods, amount and time of applied herbicide and wheat harvest time were collected during growing season by preparing questionnaire and complete them with farmers. In evaluated fields, 13 weed species belonged to 11 families were observed. Among the various parameters, field area, seed rate, certified seed application, planting date, Asian spider flower (Cleome viscosa L.) and Johnson grass (Sorghum halepense L.) had the significant effects on soybean yield. The minimum and optimum predicted yields with model were 1039 and 2036 kg/ha-1, respectively. Thus there was 996 kg/ha-1 gap between minimum and optimum predicted yield in this township. Results showed certified seed (23.07 percent), delay planting date(15.04 percent), low seed rate (11.54 percent), low field area(7.62 percent), present of Johnson grass(12.47 percent) and asian spider flower(30.25 percent) weeds were the most effective factors on this yield gap. With optimizing mentioned agronomic managements could reduce yield gap and increased yield to double.

Keywords

• Asian spider flower
• Boundary-line analysis
• Golestan providence
• Stepwise regression
• yield potential

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