Alisher Botirov - The United Graduate School of Agricultural Science, Iwate University, Morioka, Iwate ۰۲۰-۸۵۵۰, Japan
Osamu Arakawa - Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Aomori ۰۳۶-۸۵۶۰, Japan

Time of planting is a normal part of any agricultural operation. It has a particularly importance in water-challenged areas where soil moisture is an issue. During the winter months in these areas, there is usually sufficient precipitation to maintain adequate water content levels in freshly planted trees. However, during the summer and early autumn, there is very little precipitation. This can adversely affect young trees. In this study, measurements were taken to determine root growth and variations in the upper parts of apple trees that were planted in the winter, compared to those planted in the spring when planting usually takes place. To do so, one-year-old 'Miyabi Fuji', grafted onto Marubakaido (Ma) (Malus prunifolia 'Ringo') and M.9 rootstocks, were examined from January through May. The results showed dramatic changes in root growth from March (average root length less than two cm before March) to May (average root length longer than 10 cm) for both rootstocks. Furthermore, trunk moisture content increased over time (51.8% in January and 56.1% in May on M.9). Although root growth in the young apple trees occurred, it is unknown if root water absorption began before or at the same time of the root growth. Root growth developed favorably because of the soil moisture generated by the winter precipitation. We found satisfactory root growth and tree moisture content changes in the trees used in the study, leading us to recommend winter planting in areas where water resources are limited in the non-winter months.

Growing Season, Rootstock, Water content, root growth, shoot growth