Document Type : Research Paper
Authors
1 Ph.D. Student of Agronomy, Islamic Azad University, Ahvaz Branch.
2 Associate Professor, West Azerbaijan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Urmia, Iran.
3 Professor, Department of Agronomy and Plant Breeding, Faculty of Agriculture, Shahid Chamran University of Ahvaz.
4 Professor, Department of Agronomy and Plant Breeding, Faculty of Agriculture and Natural Resources, Islamic Azad University, Science and Research Branch of Tehran
5 Professor, Department of Agronomy and Horticulture, West Azerbaijan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Urmia, Iran
Abstract
Introduction. Continuous wheat cultivation and inadequate crop rotation in the dryland farming systems of West Azerbaijan Province have contributed to declining soil fertility and increasing production costs. Continuation of the current cropping pattern, as observed in many rainfed areas of the country, may threaten the long-term sustainability of crop production under dryland conditions. Previous research in Iran has demonstrated that the adoption of appropriate crop rotations, particularly the inclusion of grain legumes and annual forage legumes, can alleviate many of the limitations and constraints associated with continuous cereal cultivation and gradually improve soil productivity. The climatic conditions of the dryland areas of northwestern Iran provide opportunities for integrating a wide range of crops, including grain legumes, annual forage crops, and oilseed crops, into rotations with wheat. Conventional dryland cropping patterns, owing to insufficient crop diversity over the long term, may result in declining soil fertility and reduced resource-use efficiency. In contrast, increasing crop diversity through the inclusion of legumes such as chickpea and lentil in rotation with wheat, as well as the use of annual forage legumes and drought-tolerant oilseed crops as preceding crops, can enhance the utilization of rainfall resources. In addition, shifting sowing from spring to delayed sowing can improve rainfall water productivity. These strategies were therefore evaluated in the present study.
Methodology: A three-year field experiment was conducted to investigate the effects of sowing date and crop rotation pattern on wheat yield and yield components, as well as rainfall water productivity (RWP). The experiment was established at the Dryland Agricultural Research Institute using a split-plot arrangement within a randomized complete block design, with nine treatments evaluated under two sowing dates: spring sowing and delayed sowing. The crop rotation patterns were: (1) wheat–chickpea, (2) wheat–lentil, (3) wheat–vetch, and (4) wheat–safflower.
Research findings: Combined analysis of variance and mean comparisons across treatments showed that sowing date and crop rotation pattern had distinct effects on the wheat agroecosystem. Across all rotation patterns evaluated, delayed sowing consistently outperformed spring sowing in terms of economic yield, biological yield, and rainfall water productivity. The highest and lowest wheat grain yields were obtained under the chickpea–wheat rotation with delayed sowing (entezari) and the lentil–wheat rotation with spring sowing, reaching 1405.7 and 1108.2 kg ha⁻¹, respectively. Analysis of the effects of sowing date on rainfall water productivity indicated a significant year × sowing-date interaction. The highest economic and biological rainfall water productivity values were recorded in the first year under delayed sowing following chickpea (ERWP = 4.09), Sina safflower (BRWP = 9.54), and Maragheh vetch (BRWP = 8.53), respectively.
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