Abstract: To study the effect of bag-controlled slow-release iron fertilizer on improving iron deficiency and yellowing of pear trees, the fertilizer was packaged with ferrous sulfate and citric acid, and 6-BA was added into the fertilizer bag. Three treatments of bag-controlled slow-release iron fertilizer （HF）, spread iron fertilizer （SF） and no iron fertilizer （CK） were set up. The growth status of fine roots, leaf SPAD value and leaf active Fe content of pear trees were analyzed. The results showed that the length, volume and surface area of fine roots treated with HF were the highest, and the root length and root volume were significantly higher than those of SF and CK treatments （P<0.05）. The number of fine roots in HF and SF treatments was significantly higher than that in CK treatment during the growing season （P<0.05）. The fertilizer effect of HF treatment was slow and stable, which maintained a certain root biomass and prolonged the browning time of pear roots. Among them, the root browning time of HF treatment was the longest, reaching 54 days, followed by SF treatment for 43 days and CK treatment for 25 days, and there were significant differences among treatments （P<0.05）. In addition, HF treatment significantly increased root activity（P<0.05）. The SPAD values of HF treatment measured in July and August were significantly higher than those of SF and CK treatments （P<0.05）. In August, the active iron content of each treatment was significantly different （P<0.05）, and the active iron content of HF treatment was the highest, which was 27.36 mg/kg. The bag-controlled slow-release iron fertilizer effectively improved the utilization rate of iron in pear trees.

Key words: pear tree, bag-controlled slow-release iron fertilizer, iron utilization rate, growth of roots, leaf SPAD value