Effect of graded levels of NPK on the reproductive characters and yield of hybrid coconut COD x WCT 13

A field experiment was conducted at Coconut Research Station, Aliyarnagar, Tamil Nadu, to study the effect of graded levels of NPK fertilisation on the reproductive characters and yield of coconut hybrid Chandra Sankara (COD x WCT). The three levels of treatments of N (0, 500, 1000 g palm-1 year-1), P (0, 108,216 g palm-1 year-1) and K (0, 830,1660 g palm-1 year-1) comprised of 27 combinations, formed the treatment structure. The experiment was laid out in 33 confounded design with two replications. Application of graded doses of nitrogen and potassium increased bunches harvested, female flowers produced per inflorescence and nut yield of palms and the differences among the treatments were significant. In addition, application of graded levels of N also increased the number of functional leaves. Application of graded levels of P did not influence these characters. Application of NPK at 1000:216:1660 g palm-1 year-1 recorded a mean yield of 146 nuts and at 50 percent of the above rates a mean yield of 142 nuts palm-1 year-1 was recorded. When N was the major limiting nutrient under the framework of the experiment, the influence of other nutrients such as P and K was not much expressed, however important is their role in nutrition of palms. The data also indicated a decrease in yield of palms at 1660 g of K application during 1996-97 and 1999-2000. Trivariate extension of the quadratic model without higher order interaction terms fitted to the yield accounts for 98.3 % of the variation. The physical optimum rate of fertiliser requirement works out to 818, 130 and 1362 g palm-1 year-1 of N, P and K respectively with a yield of 159 nuts palm-1 year-1. The available N, P and K varied between 49 and 62 ppm, 69 and 139 ppm and 68 and 268 ppm respectively and their reflect on the plant nutrition of N, P and K indicated sufficiency levels in the palm. Application of graded levels of NPK fertilisers influenced the copra content and copra yield. Application of NPK at 500:108:830 g palm-1 year-1 recorded 178 g copra nut-1 and 26.0 kg copra palm-1. The CB ratio was 1.91 for the above treatment with a net income of Rs 35,509/- ha-1, while in the control treatment the net income was negative.