Meta-Analysis of the Effect of Minimum Tillage and No-Tillage on Corn Yield in Iran

Document Type : Original Article

Authors

Department of Agricultural Engineering Research, Hamedan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension organization (AREEO), Hamadan, Iran.

Abstract

The effects of different tillage methods on corn yield have been investigated in several studies. However, most of these studies cover only small geographical areas (field experiments in one region) and sometimes yield contradictory and incomplete results. The present study aims to investigate the effect of conservation tillage (minimum tillage and no- tillage) on corn yield (grain and silage) by synthesizing national research and applying the meta-analysis method. For this purpose, articles, research reports and graduate theses were reviewed between 1991 and 2025 using keywords related to tillage in corn production. After quality control, 17 studies comparing reduced tillage with conventional tillage and 14 studies comparing no tillage with conventional tillage were included in the meta-analysis using a random effects model. Based on the results obtained, the overall effect size for reduced tillage (SMD=+0.57), it can be concluded that this method increased corn yield compared to conventional tillage. minimum tillage increased grain and silage yields by 6.41 and 4.80 percent, respectively, compared to conventional tillage. Conversely, considering the effect size for no-tillage (SMD=-0.88), it can be concluded that this method reduced corn yield compared to conventional tillage. No-tillage decreased grain and silage yields by 8.55 and 5.51 percent, respectively, compared to conventional tillage. The use of minimum tillage and no-tillage method in corn cultivation requires further and long-term research.
Introduction
The continuous use of conventional tillage (plowing with a moldboard plow) in agricultural fields has led to increased soil erosion and reduced soil fertility. Soil erosion is a major environmental problem in Iran. The country’s annual erosion rate is estimated at 895 million tonnes (equivalent to 5.5 tonnes per hectare per year), while the global average annual rate is 2.2 tonnes per hectare. Soil erosion affects soil quality and crop yield. In conventional farming systems (commonly used in Iran), the effects of erosion on yield are directly related to the reduction in the amount of water that can be stored in the soil and made available by plants. To overcome this problem, conservation agriculture, which includes: (1) no or minimal soil manipulation, (2) permanent soil cover with plant residues, and (3) plant diversity and adherence to crop rotation principles, is recommended. The effectiveness of conservation agriculture in controlling runoff and soil erosion has been proven, and it is expected to ultimately have a positive effect on crop yield. The effect of different tillage methods on corn yield under Iranian conditions has been investigated in several studies. However, most of these studies cover only limited areas (field experiments in one region), which sometimes have contradictory and incomplete results. The purpose of this research is to investigate the effect of conservation tillage (minimum tillage and no- tillage) on corn yield by synthesizing national studies with meta-analysis method.
 
Materials and Methods
This research aims to investigate the effect of minimum tillage and no-tillage on yield of corn using national studies and research and applying the meta-analysis method. For this purpose, articles, research reports and graduate theses between 1991 and 2025 were reviewed using keywords related to tillage in corn. Finally, after quality control, 17 studies were selected to compare minimum tillage method with conventional tillage and 14 studies were selected to compare no-tillage with conventional tillage using a random effects model. The data required for meta-analysis are the treatment mean (  standard deviation ), and the number of replicates or sample size (n) in the experimental design. In data analysis, the standardized mean difference parameter, which is a key measure of effect size, was used between the control treatment (conventional tillage) and the experiment (conservation tillage).
Results and Discussion
Based on the results obtained, the effect size for the minimum tillage method (SMD=+0.57) indicates that the minimum tillage method has increased corn yield compared to conventional tillage. Minimum tillage increased grain yield by 6.41 % compared to conventional tillage. The average total yield of grain corn in conventional tillage and minimum tillage methods was 8244.6 and 8871.9 kg/ha, respectively. After weighting each yield, the average weighted yield of conventional tillage and minimum tillage methods was 740.3 and 787.7, respectively. Also, minimum tillage increased the yield of silage corn by 4.80% compared to conventional tillage. The average total yield of forage corn in the conventional tillage and minimum tillage methods is 51822.6 and 55940.6 kg/ha, respectively. After weighting each yield, the average weighted yield of the conventional tillage and minimum tillage methods was 7748.7 and 8120.8, respectively. The probability values in the Begg and Egger method (for estimating publication bias) were 0.002 and 0.037, respectively (less than 10 percent), which allows us to conclude that there is evidence of publication bias in studies comparing the minimum tillage method with conventional tillage in corn production. Considering the effect size of the no-till method (SMD = -0.88), it can be concluded that the no-till method has reduced corn yield compared to the conventional tillage method. No-till reduced the yield of grain corn by 8.55% compared to conventional tillage. The average total yield of grain corn in the conventional tillage and no-till methods is 8903.3 and 7980.2 kg/ha, respectively. After weighting to each of the yields, the average weighted yield of the conventional tillage and no-till methods was 1116.5 and 1021.0, respectively. Also, no-till reduced the yield of silage corn by 5.51% compared to conventional tillage. The average total yield of silage corn in the conventional tillage and no-tillage methods is 56449.3 and 53205.2 kg/ha, respectively. After weighting each yield, the average weighted yield of the conventional tillage and no-tillage methods was 9421.5 and 8902.5, respectively. The probability values in the Begg and Egger method (for estimating publication bias) were 0.09 and 0.055, respectively (less than 10 percent), which allows us to conclude that there is evidence of publication bias in studies comparing no-till with conventional tillage in corn production.
Conclusion
The minimum tillage method increased the yield of grain corn (6.41%) and silage corn (4.80%) compared to the conventional tillage method, whereas the no-tillage method decreased the yield of grain corn (-8.55%) and silage corn (-5.51%). The use of minimum tillage and no-till methods in corn farming requires further and long-term research.

Keywords

Main Subjects

References

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History

  • Receive Date: 17 December 2025
  • Revise Date: 25 August 2026
  • Accept Date: 25 August 2026

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