بررسی خلأ عملکرد و عوامل مؤثر بر آن در گندم‌زارهای آبی شهرستان ازنا، استان لرستان، ایران، با استفاده از روش تحلیل مقایسه کارکرد (CPA)

Introduction
Wheat is the most important plant affecting human life in various ways, and due to its high adaptability to different conditions, it is planted and harvested almost year-round across the globe. However, given the diverse management practices of farmers, the potential of the land is often not optimally utilized, resulting in low yields per unit area. This issue is a significant problem in wheat fields that needs to be examined through field methods. The CPA method effectively estimates yield differences based on the potential of the land and the yield resulting from farmers' management. Therefore, this research was planned and implemented to investigate the yield gap and its contributing factors in the irrigated wheat fields of Azna County, Lorestan, using the CPA method.

Materials and methods
In this study, data from 74 irrigated wheat farms in Azna were used to estimate the yield gap and its contributing factors through the CPA method. The collected data from the wheat fields were gathered using a questionnaire that included farm characteristics(rural area, farmer experience and literacy, field area and rotation), planting operations(planting date, plowing, subsoiler, cultivator and trowel, disk and its number, planting method, fungicide, variety, seed quantity, amount, type, method and time of spreading nitrogen, phosphorus and potash fertilizers, amount and type of livestock manure), maintenance operations(type, irrigation frequency, irrigation in autumn and its number, first irrigation in spring, amount, time and method of top-dress nitrogen fertilizer, pest and weed control), and harvesting operations(harvest date and length of wheat growth period). Topographic(aspect, slope and elevation of wheat fields) and soil information(organic matter, pH, available phosphorus and potassium, total nitrogen and soil texture) for each wheat field was obtained from GIS-prepared layers based on their geographical locations. To determine the yield model(output), the relationship between all measured variables and yield was examined using stepwise regression analysis with SAS software. Finally, using the derived production equation, the yield gap and its contributing factors, along with the share of each, were identified.

Research findings
The results of this study showed that the average, minimum and maximum yield estimated by the model were 5906.62, 3248.22 and 11289.24kg.ha-1, respectively and the total yield gap was 5382.62kg.ha-1. The average observed yield of wheat fields was 5943kg.ha-1, the minimum was 2500kg.ha-1 and the maximum was 8500 kg.ha-1. The correlation between the estimated yield and the actual yield of farmers was 0.66 and RMSE was 842.71 kg.ha-1and the coefficient of variation of the model was14.27%. The analysis of the factors contributing to the yield gap indicated the role of six variables: low organic matter in the soil(26.8%), lack of row planting(3.60%), low seed usage(10.96%), reduced number of irrigations in the fall(18.88%), reduced amounts of nitrogen applied as Top-dressing fertilizer(17.28%), and untimely harvesting(22.43%) in creating the yield gap in farmers' wheat fields.

Conclusion
The final conclusion confirms the acceptable capability of the CPA method in estimating the yield gap and the factors affecting it in the wheat fields of Azna. It indicates that with timely, targeted, and intelligent management, the yield gap can be reduced by approximately48%, thereby significantly increasing wheat production. Implementing appropriate crop rotation, managing wheat and other crop residues, using animal manure, promoting the use of row planters and providing them to farmers, managing seedbed preparation, selecting suitable varieties, and strongly recommending fall irrigation, soil testing to determine appropriate nitrogen fertilizer levels, and distributing it according to the growth stages of wheat, along with precise planning to avoid overlap in spring crop cultivation with wheat harvesting and timely entry of harvesting machinery into wheat fields are recommended to reduce the yield gap based on the influencing factors.