Malaysian Journal of Soil Science (MJSS)
Abstracts and Full Texts: Vol.
09
Aggregate Breakdown Rates of Some
Malaysian Soils and Relation to Aggregate Properties
TEH.
C.B.S., T. JAMAL. & S. NURANINA
The objectives of this study were to determine the
rate of aggregate breakdown of three aggregate sizes from
three highly-weathered Malaysian soils and relate the
aggregate breakdown rate with several aggregate constituents.
Bungor, Munchong and Serdang soils (from orders Ultisol and
Oxisol) were used. For each soil type, three macro-aggregate
size fractions were separated: 3-5, 1-2 and
0.3-0.5 mm. Each aggregate size fraction was wet-sieved for
six time durations to determine breakdown rate of aggregates
with time. Each aggregate size fraction was also analysed for
its texture, organic carbon, total nitrogen, cation exchange
capacity, free iron oxides, humic acids, fulvic acids and
polysaccharides. Results showed that the breakdown rate of
aggregates followed an exponential relationship with time.
This meant that aggregates would be particularly sensitive to
disruptive forces during the initial periods of erosion by
water. The breakdown rate of aggregates was primarily related
to the amounts of clay, sand and fulvic acids. However,
whether aggregates stability increased or decreased with
aggregate size depended on both the soil type and aggregate
size in question. This was because the distribution patterns
of the aggregate constituents were dissimilar to each other,
and their distribution patterns depended on both soil type and
aggregate size. For a given soil type, the distribution of
clay silt and sand differed among the macro- aggregate size
fractions. Though the distributions of other aggregate
constituents (organic carbon, total nitrogen, cation exchange
capacity, free iron oxides, humic acids and polysaccharides)
among the aggregate sizes were statistically similar, they
differed according to soil type.
Measured and Modelled Soil Water
Characteristic Curves for a Sandy Loam Soil
M.S.
MIRJAT, M. RODGERS, J. MULQUEEN & P.
GIBBONS
Soil water characteristic (SWC) curves
were established for various depths ranging between 0.05 and
1.5 m in a free draining sandy loam soil with a deep
watertable the laboratory and between 0.2 and 2 m depth in the
field. In the laboratory, drying curves were established
applying incremental suctions and measuring corresponding
water contents, while in the field, soil suction and water
contents various depths were measured by tensiometers and
neutron probes, respectively during infiltration and drainage.
The SWC curves established in the laboratory were analysed
using models proposed by Campbell (1974), van Genuchten (1980)
and Fredlund and Xing (1994). In general, the three models
fitted well to the measured data exceptCampbell’s model which
overestimated the soil water content near saturation. The
Campbell’s model followed a
linear fit to the data when plotted on a semi-log scale,
whereas van Genuchten’s and Fredlund and Xing’s models
followed a classical non-linear curve silhouette. Both models
seem to accurately predict the soil water content for the
entire suction range
applied in this study. Based on the results of study,
it is suggested that the established SWC curves be used to
estimate unsaturated soil functions in similar soil conditions
in
Ireland
and
elsewhere.
Adsorption, Desorption and Mobility of
Metsulfuron Methyl Herbicide in Malaysian Agricultural Soils
SARASWATHY SINNAKKANNU, ABDUL RANI ABDULLAH
& MHD RADZI ABAS
The adsorption, desorption and mobility of
metsulfruon methyl, a commonly used herbicide in
Malaysia, was
investigated in some selected agricultural soils namely
Persit, Segamat, Kiol, Sedu and Penor as a means to understand
the potential of the herbicide to contaminate the Malaysian
soil environment. The range of organic matter content of the
soil samples was 2.3 to 33.8, while the range of pH was 3.2 to
6.5.
The adsorption of metsulfuron methyl to soils was
found to best fit a Freundlich adsorption isotherm with
distribution coefficients (Kd)
ranging from 0.45 - 46.23. A
positive correlation (r= 0.95)
between organic matter content and adsorption was
observed, while a significant negative correlation (r=-0.82 1)
was seen between soil pH and adsorption. The extent of
desorption of metsulfuron methyl was also observed to decrease
with increasing organic matter content of the soil. Simulated
rainfall following the application of metsulfuron methyl at a
field application rate of 75 g/hectare in the Segamat soil
resulted in the leaching of the herbicide to up to 15 cm of
the soil column. Much of the chemical was found in the 10-15
cm zone of the packed column. Complete leaching of the
chemical through the soil column was not observed under the
conditions of the present study, as the chemical was not
detected in the leachate. It was observed that the influence
of organic matter content and soil pH was consistent with
reports on soils from temperate countries. It was also noted
that the relatively low pH, low organic matter content and
high clay content of the Segamat soil resulted in limited
leaching of the chemical.
Domestic Sewage Sludge Application to an
Acid Tropical Soil: Part I. Sludge as an N Fertilizer
for Maize
ROSAZLIN A., I.
CHE FAUZIAH, A.B.
ROSENANI & S. ZAUYAH
Land application of sewage sludge is considered
the most economical: it also provides an opportunity to
recycle beneficial plant nutrients and organic matter to soil
for crop production. The application of sewage sludge as a
source of N fertiliser for maize production was investigated
in this study. Application of sewage sludge or inorganic N
fertiliser ((NH4)2SO4)
produced significantly higher yields than the control (without
N). The rate of 420 kg N ha-1 sewage sludge gave
the highest dry matter yield for the 1st cycle and
746 kg N ha-1
sewage sludge for the 3rd cycle. It can be
concluded that sewage sludge performs just as good as
inorganic fertiliser as a source of N fertiliser. However, in
the 2nd cycle, mineralisation of sewage sludge was
slow because of the dry period during this cycle. For sludge
to perform as efficiently as fertiliser, good moisture
conditions are necessary for N mineralisation to take place.
Soil Tilth Index for Malaysian Paddy
Fields
S.M.
BOCKARI-GEVAO, W.I. WAN ISHAK , Y. AZMI & C.B.S.
TEH
Tillage treatments have been an integral part of
many soil and crop management studies on the multifaceted
concept of soil tilth. If soil tilth can be represented as a
tillage index, it could be used to schedule farming operations
and to improve soil management, which will consequently lead
to sustainable, productive and profitable agriculture. This
study was undertaken to investigate the effect of rotary
tillage on some soil physical properties (bulk density, cone
index, plasticity index, aggregate uniformity coefficient) and
organic matter, and to develop and evaluate a soil tilth index
based on changes of these soil properties. The tillage
treatments were factorial combinations of forward speeds
obtained with four selected tractor transmission gears (Gear 1
High, Gear 2 Low, Gear 3 Low and
Gear 4 Low) and three rotary tilling speeds (140 rpm, 175 rpm
and 200 rpm) of commonly used tillage implements in Malaysian
paddy fields. Experimental results indicated an overall
decrease in bulk density cone index, plasticity index and
organic matter, after tillage treatments. Analysis of variance
indicated significant differences (p<0.01) among the
rice yield means. Bulk density, cone index and plasticity
index were identified to have fairly high positive correlation
with the yield (r>0.30). A tilth
index was consequently developed with bulk density, cone index
and plasticity index which gave a better linear relationship
(R2 =
0.56) with rice yield than when
individual soil properties were considered. Results of the
study suggest that tilth index may assist in yield prediction
by comparing measured soil conditions in a paddy field.
The Limiting Factors of Sand Bed Reactor
for Heterotrophic Denitrification Process in Tropical
Conditions
SARWOKO
MANGKOEDIHARJO
(Full Text-pdf-4.81MB)
This
research was carried out in a sand bed reactor for
heterotrophic denitrification processes. A solution mixture of
24 mg nitrate-N/L and 64mg methanol-CH3OH/L was
prepared for an influent of eterotrophic reactor. Influent pH
level was maintained at 6.5 with the operating temperature in
the range of 20 — 35°C. By adjusting
nitrogen volumetric loading (NVL) and phosphorus
concentrations at tropical operating conditions, it was found
that the detention time in the reactor and the phosphorus
concentrations of influent were the limiting factors for
heterotrophic denitrification process to assure free-nitrite
effluent. The maximum detention time was 1 hour and the
phosphorus concentrations were 0.4 — 0.6 mg P/L for suppressed
nitrite accumulation. The maximum NVL of 0.6 g N/day/L reactor
achieved a maximum denitrification efficiency of 94%. The use
of 64 mg glucose-C6H12O6/L
resulted in maximum denitrification efficiency of 98%, while 64
mg acetic acid-CH3COOH/L only offered a maximum
denitrification efficiency of
88%. |
