Hameed Khan, H.Biddappa, C.C.Nagarajan, M.George V. ThomasCecil, S.R.2014-07-212014-07-211992J.Plantn.Crops 1992 Suppl. v-20 p-14-18http://hdl.handle.net/123456789/4358Skipping of phosphorus application to adult coconut palms has resulted in reduction of salt available P in manuring circle (0-90 cm) from 43.88 ppm to 12.72 ppm over a period of 14 years and alto had no deleterious effect on P nutrition and yield of palms indicating residual effectiveness of phosphorus. Application of P at two levels showed no advantage in further enhancement of P nutrition and yield. The mean soil available P was 12.72, 30.43 and 53.29 ppm in P-0, P-1 (160 g P2O5, palm-1 year-1) and P-2 (320 g P2O5 palm-1 year-1) respectively. N, P, K. Ka, Ca, Mg, Fs, Mn, Zn, and Ca contents of the palm (Frond 14) were alto net significantly different among the treatments and ware In sufficiency range. Interestingly, VA mycorrhizal infection was more In the P-O treatment (79.3%) compared to P-1 (52.1%) end P-2 (47.1%). Population of P zolubilizing bacteria was also higher In P-0 treatment indicating the involvement of microbial population in P nutrition of coconut. The mean yield of the palms (1989) viz., 109.07, 102.36 and 108.71 nuts palm-1 per year-1 in P-0, P-1 and P-2 treatments respectively and the cumulative yield for four years did not show significant differences among the treatments, it was indicated that residual phosphates of 40 ppm in 0-90 cm in depth in the basin could sustain adquate P nutrition and normal yields for 14 years. Also sail available phosphorus status of 10-12 ppm maintained sufficiency level of P in the coconut palm. Soli available P of less than 10 ppm warrants full recommended dose to be applied (P2) and soils testing 10-28 ppm need only 59% of recommended dote (P1). For soils testing more than 20 ppm, application of phosphorus can be withheld for certain years.enArticle