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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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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