Horizontal and vertical movement of potassium in the Neyyattinkara-Vellayani soil association from a long term fertilizer experiment under coconut
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Date
1989
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Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani
Abstract
The present study aims at finding out the movement pattern of applied potassium in the long term fertilizer trial under coconut. The other targets are to find out the suitable site for soil sampling from coconut garden for nutritional studies. The investigation is done by taking surface and surface samples from four sites away from bole of the coconut palm at 90 cm interval. Of this the second site coincides with the site of fertilizer application (180 cm away from bole). In addition to this, for finding out the extent of leaching, three profiles were dug at the site of fertilization in the K0, K1 and K2 treatments with highest dose of N and P combination. Soil samples are collected at 15 cm interval from the profiles upto 105 cm. Leaf samples from 14th frond also collected simultaneously. These samples are collected from a permanent fertilizer trial under coconut which is on going in the coconut Research station, Balaramapuram. This is a 33 NPK, factorial confounded experiment with two replications.
Exchangeable, water soluble and non – exchangeable potassium is determined in all the soil samples collected. In addition to this soil separates, CEC, organic matter, pH, Calcium content and Magnisium content also found out.
The water soluble, exchangeable and non – exchangeable K values are compared among different sites of sampling and depths in order to broughtout the effect of application of potassic fertilizer for the last 24 years in the soil. The values of different forms of K is correlated with soil characteristics to fine out the impact of various characters in the mobility of potassium. A multiple linear regression analysis is carried out with the leaf nutrient concentration as a dependant variable and the available K at sampling points as independent variable.
A clear conical movement pattern is obtained in case of water soluble and exchangeable K. The non – exchangeable K did not show an increase in concentration as a result of addition of potassium fertilizer. The water soluble and exchangeable K were distributed within the root zone of the palm. The leaching of K is upto 75 cm from the surface. It cannot be considered as lost because coconut has sufficient root distribution in this zone. Higher doses of application of K did not move to greater depths than that of medium dose.
The mobility of applied K is affected by soil properties like coarse sand fraction, clay fraction, CEC and organic matter. Increase in sand fraction increased the movement K to subsurface layers. But clay fraction has a negative correlation.
The index leaf k level has a positive correlation with the available K at various sampling points. The leaf K content is influenced most by the available K level at the subsurface layer of second sampling site (180 cm from bole). Thus, the soil sample for nutrient analysis should be derived from the 30 – 60 cm layer of 180 cm away from the base of the palm.
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170188