Meta-analysis of the effect of conservation tillage on irrigated wheat yield in Iran

Conservation tillage can be an alternative system to conventional tillage of irrigated wheat crops in Iran due to its potential for protecting soil and water resources and reducing production costs. Many studies in Iran have investigated the effect of different tillage methods on various factors, such as yield, soil physical properties, costs, etc., in irrigated wheat cultivation. All available studies were systematically reviewed to gain a better perspective on the impact of tillage methods on wheat yield in Iran, and their findings were analyzed by meta-analysis. All articles published in Iranian journals, final reports of research projects, and related articles presented at congresses and student dissertations were reviewed using standard keywords Then, the articles and reports published in this field with the criteria for entering the research were entered into the meta-analysis after quality control using a random model. Finally, 40 studies were selected to compare minimum tillage methods with conventional tillage, and 21 were selected to compare no-tillage with conventional tillage. The results showed that the effect size (SMD) in minimum tillage and non-tillage methods were -0.42 and -1.18, respectively, indicating the negative effect of these methods on yield. Reduced tillage methods significantly reduced wheat yield (-2.87%) compared to conventional tillage. Also, no-tillage significantly reduced yield (-8.2%) compared to conventional tillage. Minimum tillage methods did not have much effect on reducing wheat yield. It is suggested that one of the minimum tillage methods, including 1- Chiselpaker, 2- combined tiller (chisel plow equipped with rollers), 3- chisel plow + disc, and 4- disc according to the facilities and access of each area to these tools, replaced conventional tillage (moldboard plow + disc harrow + leveler).