Introduction: Fruit thinning is an effective technique for controlling fruit number and size, defined as the removal of certain flowers or fruits during their early stages of development. Kiwifruit growers often exhibit reluctance toward deciding on thinning operations due to concerns over the potential negative impact on yield, and consequently, on total revenue. Furthermore, a lack of precise knowledge among many growers regarding the appropriate timing and methodology of thinning, leading to their inaction. Therefore, developing a suitable model to define the execution protocol for thinning is essential to ensure the maximum economic return for the crop. Among the most reliable decision-making methodologies, Analytic Hierarchy Process (AHP) stands out as one of the most widely used techniques for solving Multi-Criteria Decision-Making (MCDM) problems, owing to its numerous capabilities and features. This study aimed primarily at investigating the economic justification of thinning the Hayward kiwifruit cultivar at various intervals. For this purpose, the Analytic Hierarchy Process (AHP) and Grey Analytic Hierarchy Process (GAHP) methods were employed to assign weights to the relationship between fruit quality grades and thinning dates, thereby, determining how the thinning practice can lead to enhanced production revenue.
Materials and Methods: In order to carry out this research, there were used five fruit quality evaluation criteria including premium grade, grade I, grade II, grade III, and out-of-grade fruits and also considered five alternatives, including thinning times at 15, 30, 45, and 60 Days After Fruit Set (DAFS) as well as ‘no thinning’ as a control treatment alternative. Data analysis was performed based on pairwise comparisons regarding the five criteria of the decision tree, utilizing both AHP and GAHP to rigorously assess subjective expert judgments. This multi-method approach was chosen to enhance the robustness of the decision-making framework by incorporating both AHP and GAHP evaluation techniques for subjective ranking. The quantitative basis for these comparisons was derived from the wholesale prices of kiwifruit in Guilan province of Iran.
Results and Discussion: The study results showed that the criterion of premium grade fruit with an average relative weight of 0.490 had the most important role among all criteria; also, the criterion of grade I fruit with an average relative weight of 0.286 was ranked the second. As shown by the results, the criterion of the grade II fruit with the average relative weight of 0.132 was in the third place, while the out-of-grade fruit and grade III fruit were ranked the fourth and fifth with 0.046 and 0.044, respectively. In addition, the final comparison of the relative weight of the studied alternatives compared to the target showed that the thinning treatment in 30 DAFS had the highest relative weight (0.236) among all alternatives compared to the target, which is the best thinning time for Hayward kiwifruit. The thinning at 15 DAFS with an average relative weight of 0.215 was ranked the second in importance, and the thinning operations at 45 and 60 DAFS with averages of 0.207 and 0.183 were ranked the next in importance, respectively. The alternatives were compared to the target and the control had the lowest weight with a rate of 0.158. The findings of the conventional AHP and the Gray AHP (GAHP) showed that the criterion of premium fruit had the greatest effect on the revenue of kiwifruit growers; so, horticultural operations should be directed towards producing more premium fruit. This indicated that thinning in one month after fruit set had a greater effect on producing higher quality fruits and, as a result, greater economic value than other thinning times. Also, fruit thinning at different times had a significant effect on increased economic performance of vines so that the total economic performance of each Hayward kiwifruit vine would increase as a result of thinning compared to the control vine. 
Conclusion and Suggestions: The results obtained from this research showed that different fruit thinning times had certain significant effects on the revenue and weight of different quality grades of Hayward kiwifruit; and timely fruit thinning in Hayward kiwifruit led to the production of fruits with the same size and shape by changing the process of distribution of carbohydrates between fruits. The results obtained from the total revenue in each treatment indicated that regardless of the time of the thinning operation, despite the removal of malformed and abnormal fruits that led to a decrease in the production of grade II fruit, there was a change in the quality of production from grade II fruit to grade I fruit, while this change was also observed from grade I fruit to premium grade fruit. This proves that the quality performance is more important than the weight performance in the production of Hayward kiwifruit and is effective in increasing the revenue of growers. In general, the study results showed that the kiwifruit thinning is economically viable, so it can be suggested to the kiwifruit growers to perform thinning, especially the thinning of malformed and abnormal fruits, 30 DAFS.