Root activity patterns of some tree crops. Technical reports series No. 170. Results of a five-year coordinated research program of the Joint FAO/IAEA Division of Atomic Energy in Food and Agriculture

Using a $sup 32$P solution soil injection technique, seasonal root activity was studied. In most of the crops, root activity was highest near the soil surface, within the top 20 cm. The exceptions were orange trees in Spain, in which root activity was highest at 30 cm depth, and the dry season root activity of coffee in Kenya which was highest at 45 to 75 cm depth. In general, banana, young orange trees in Spain, mature coffee and coconut trees showed highest lateral root activity within 30 to 100 cm distance from the trees. In young citrus trees in Taiwan, mature orange in Spain, mature cocoa and oil palm trees in Malaysia, lateral root activity was highest at 100 to 300 cm distance. In the Ivory Coast the lateral root activity of mature oil palms was independent of distance from the tree within the 100 to 400 cm distance tested. In wet and warm seasons all crops showed more intense root activity than in dry and cold seasons. In dry weather, the differences between root activity near the soil surface and lower depths were less than in wet seasons. There were no marked seasonal variations in patterns of root activity.more » Experimental data indicate that patterns of root activity can vary with soil type, tree variety and age. These are some areas for future research. Fertilizer placement experiments using $sup 32$P labeled fertilizers on coconut, citrus, cocoa and coffee trees showed that application within the zones of highest root activity resulted in highest utilization by both the treated tree and neighboring trees. (auth)« less