Wahid, P AAnilkumar, K SKAU2019-05-102019-05-101987171156http://krishikosh.egranth.ac.in/handle/1/5810102679PGAn investigation on the root activity pattern of coconut palm (Cocos nucifera Linn.) and the influence of long term application of NPK fertilizers was conducted at the College of Horticulture, Vellanikkara. The coconut variety West Coast Tall was invariably used for the study. It was found that major portion of the active roots of coconut were within an area of 2 m radius around the palm. The vertical distribution of active roots was mainly confined to a depth of 30-60 cm and the root activity decreased sharply at 90 cm depth. The surface 25 cm soil layer is practically devoid of roots. Based on these results it is suggested that the fertilizers may be applied to an area of 2 m radius around the palm for their maximum utilization. Root activity was positively correlated with organic carbon, available P, available K, available Mn and Zn and negatively correlated with exchange acidity. Studies on the effect of long term NPK fertilization on soil chemical characteristics revealed that regular application of ammonium sulphate reduced the soil pH markedly (from 4.88 in N0 plots to 4.38 in N2 plots). A decrease in available Mn and an increase in available S also observed with continuous N fertilization. Continuous P fertilization, improved available P status of soil from 5.65 ppm in P0 plots to 146.45 ppm in P2 plots. Heavy build up of available P also noticed in lower layers with continuous P fertilization. Application of superphosphate reduced K status of soil probably due to replacement by Ca in exchange sites. Continuous application of muriate of potash increased the available K content as well as organic carbon content of soil. The effect on exchangeable K in soil is found to be N-dependent as revealed from the significant N x K interaction. Significant positive correlations were observed between soil available K in the 0-25, 50-75 and 75-100 cm depths and the levels of K in 6th and 14th fronds. Available K in the 0-25, 50-75 and 75-100 cm soil layers is positively correlated with yield. Organic carbon at 0-50, 25-50 and 75-100 cm soils depths also showed positive correlation with yield. Among the micronutrients studied Fe and Cu (25-50 cm soil layer) and Zn (50-75 cm soil layer) showed positive correlations with yield. Foliar Mg and Mn levels decreased with increasing rates of K fertilizations, while N fertilization increased foliar Mn content. Nitrogen fertilization also increased foliar N and Ca contents. Potassium levels in 6th and 14th fronds showed significant positive correlations with yield (r’values 0.500** and 0.544** respectively). The critical K level found by Fremond et al.(1966) (0.8 to 1.0%) need a revision as significant yield increase was observed even at foliar K levels of 2.15 to 2.62 ppm in 14th and 6th leaf respectively of the experimental palms.ennullThesis