Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New Guinea

The present study attempts to employ potassium (K) release parameters to identify soil-quality degradation due to changed land use patterns in sweet potato (<i>Ipomoea batatas</i> (L.) Lam) farms of the highlands of Papua New Guinea. Rapid population increase in the region increased pres...

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Main Author: B. K. Rajashekhar Rao
Format: Article
Language:English
Published: Copernicus Publications 2015-02-01
Series:Solid Earth
Online Access:http://www.solid-earth.net/6/217/2015/se-6-217-2015.pdf
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spelling doaj-fa634e11809f4e5a8381e59d2fc132952020-11-25T00:43:59ZengCopernicus PublicationsSolid Earth1869-95101869-95292015-02-016121722510.5194/se-6-217-2015Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New GuineaB. K. Rajashekhar Rao0Department of Agriculture, Papua New Guinea University of Technology, Lae 411, Papua New GuineaThe present study attempts to employ potassium (K) release parameters to identify soil-quality degradation due to changed land use patterns in sweet potato (<i>Ipomoea batatas</i> (L.) Lam) farms of the highlands of Papua New Guinea. Rapid population increase in the region increased pressure on the land to intensify subsistence production mainly by reducing fallow periods. Such continuous cropping practice coupled with lack of K fertilization practices could lead to a rapid loss of soil fertility and soil-resource degradation. The study aims to evaluate the effects of crop intensification on the K-release pattern and identify soil groups vulnerable to K depletion. Soils with widely differing exchangeable and non-exchangeable K contents were sequentially extracted for periods between 1 and 569 h in 0.01 M CaCl<sub>2</sub>, and K-release data were fitted to four mathematical models: first order, power, parabolic diffusion and Elovich equations. Results showed two distinct parts in the K-release curves, and 58–80% of total K was released to solution phase within 76 h (first five extractions) with 20–42% K released in the later parts (after 76 h). Soils from older farms that were subjected to intensive and prolonged land use showed significantly (<i>P</i> < 0.05) lower cumulative K-release potential than the farms recently brought to cultivation (new farms). Among the four equations, first-order and power equations best described the K-release pattern; the constant <i>b</i>, an index of K-release rates, ranged from 0.005 to 0.008 mg kg<sup>−1</sup> h<sup>−1</sup> in the first-order model and was between 0.14 and 0.83 mg kg<sup>−1</sup> h<sup>−1</sup> in the power model for the soils. In the non-volcanic soils, model constant <i>b</i> values were significantly (<i>P</i> < 0.05) higher than the volcanic soils, thus indicating the vulnerability of volcanic soils to K deficiency. The volcanic soils cropped for several crop cycles need immediate management interventions either through improved fallow management or through mineral fertilizers plus animal manures to sustain productivity.http://www.solid-earth.net/6/217/2015/se-6-217-2015.pdf
collection DOAJ
language English
format Article
sources DOAJ
author B. K. Rajashekhar Rao
spellingShingle B. K. Rajashekhar Rao
Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New Guinea
Solid Earth
author_facet B. K. Rajashekhar Rao
author_sort B. K. Rajashekhar Rao
title Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New Guinea
title_short Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New Guinea
title_full Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New Guinea
title_fullStr Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New Guinea
title_full_unstemmed Kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of Papua New Guinea
title_sort kinetics of potassium release in sweet potato cropped soils: a case study in the highlands of papua new guinea
publisher Copernicus Publications
series Solid Earth
issn 1869-9510
1869-9529
publishDate 2015-02-01
description The present study attempts to employ potassium (K) release parameters to identify soil-quality degradation due to changed land use patterns in sweet potato (<i>Ipomoea batatas</i> (L.) Lam) farms of the highlands of Papua New Guinea. Rapid population increase in the region increased pressure on the land to intensify subsistence production mainly by reducing fallow periods. Such continuous cropping practice coupled with lack of K fertilization practices could lead to a rapid loss of soil fertility and soil-resource degradation. The study aims to evaluate the effects of crop intensification on the K-release pattern and identify soil groups vulnerable to K depletion. Soils with widely differing exchangeable and non-exchangeable K contents were sequentially extracted for periods between 1 and 569 h in 0.01 M CaCl<sub>2</sub>, and K-release data were fitted to four mathematical models: first order, power, parabolic diffusion and Elovich equations. Results showed two distinct parts in the K-release curves, and 58–80% of total K was released to solution phase within 76 h (first five extractions) with 20–42% K released in the later parts (after 76 h). Soils from older farms that were subjected to intensive and prolonged land use showed significantly (<i>P</i> < 0.05) lower cumulative K-release potential than the farms recently brought to cultivation (new farms). Among the four equations, first-order and power equations best described the K-release pattern; the constant <i>b</i>, an index of K-release rates, ranged from 0.005 to 0.008 mg kg<sup>−1</sup> h<sup>−1</sup> in the first-order model and was between 0.14 and 0.83 mg kg<sup>−1</sup> h<sup>−1</sup> in the power model for the soils. In the non-volcanic soils, model constant <i>b</i> values were significantly (<i>P</i> < 0.05) higher than the volcanic soils, thus indicating the vulnerability of volcanic soils to K deficiency. The volcanic soils cropped for several crop cycles need immediate management interventions either through improved fallow management or through mineral fertilizers plus animal manures to sustain productivity.
url http://www.solid-earth.net/6/217/2015/se-6-217-2015.pdf
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