Soil injection of carrier-free ³²P was used to study the root activity distribution in 4 important fruit crops. The results indicated that all the 4 citrus varieties (Kagzi line, sweet orange cv Mosambi, Coorg mandarin and Kinnow mandarin) were shallow-rooted while grape (both 'Anab-e-Shahi' and ‘Thompson seedless'), mango ('Alphonso') and guava ('Arka Mridula') were deep-rooted in nature. The spread of active roots was uniform during north-east monsoon period due to uniformly moist soil mantle. During summer the active roots moved toward soil surface and away from the trunk toward the periphery of the drip-circle. The intensity of root activity was maximum during noth east monsoon due to high volumetric soil moisture and decreased during winter as the rains receeded. Least activity was observed during summer due to depletion of soil moisture. Generally the period of high root activity alternated with that of shoot growth except in guava in which both high root activity and shoot activity coincided. The results were useful to adjust the time and placement of fertilizer during the year to achieve maximum fertilizer use efficiency from experiments using labelled fertilizers.