Studies on the methods of inorganic nutrient application in coconut

Summary Using carrier free³²P, tagged single superphosphate and⁸⁶Rb, the efficiency of different methods of plant injection and soil placement techniques for fertilizer application was examined. In the plant injection techniques the radioactivity was fed to the palms through growing roots tips, cut ends of roots, stem injection and leaf axils. The application of radioactivity through the cut ends of roots was most efficient since³²P was detected in 10 m tall palms, four hours after application. In stem, leaf axil and growing roots tips injection the³²P was detected after 8, 12 and 18 h. Out of four methods of soil application, the quickest recovery of³²P in the palms was detected after 7 days of placement when applied by the hole method. The³²P activity in the palms through circular trenches, strips and basin methods was recorded after 8, 8 and 11 days of application respectively. The accumulation of⁸⁶Rb was significantly higher than³²P. With plant injection technique the accumulation of activity was found to be significantly higher than with soil placement methods. The rate of radioactivity absorption was 10 to 60 time faster in the former technique as compared to that of the latter. The application of radioactivity through cut ends of roots and circular trench methods, were found to be better and may be recommended for nutrient application in coconut.