Citation
Kertonegoro, Babang Djadmo
(2000)
Marling a Regosol of Central Java and its Effect on Maize Crop Performance.
Doctoral thesis, Universiti Putra Malaysia.
Abstract
In this study, a sandy soil (Regosol) derived from volcanic debris is amended with
clay soils (Latosol and Grumusol) taken from different localities, with the objective
of increasing the productivity of the Regosol as a marginal land.
Soil samples taken :from the top 30 em of the soil surfuce are dried, ground, and
passed through a sieve with 2.0 mm openings. The Regosol is then thoroughly
mixed with the Latosol or Grumusol based on oven weight percentage of 0010, 10%,
20%, 30%, 40% ,50%, and 100% of the Latosol or GrumusoL
Mineralogical analyses indicate that the sandy soil (Regosol) is mainly dominated by
feldspars and cristobalite while the clay Latosol contains mainly 1:1 type clay
minerals of the kaolinite type and most probably layers of halloysite, metahalloysite
or kaolinite, with some crlstobalite in it. The Grumusol, on the other hand, is
dominated by open 2:1 clay minerals (swelling clay, smectite) mixed with 1:1 type
such as halloysite, metahalloysite or kaolinite. The addition of clay soils to the sandy soil changes the textural class towards clay.
The particle density and the bulk density of the soil mixture decrease. The total
porosity increases. The oxygen diffusion rate (ODR) in the soil mixture is influenced
by the water content. Most of the ODR curves are lifted sharply when the matric
potential decreases below - 2 kPa. The saturated hydraulic conductivity declines
significantly after the addition of 10% to 20% of clay soils. Mixtures containing
more than 40% clay soil show similar patterns as those of the original clay soils,
while those containing less than 40% clay soil show intermediate behaviour between
the sandy soil and the clay soils. The addition of 30% of clay soil causes a
substantial reduction in the rate and maximum height of capillary rise during a ten hour
period of observation.
With increasing amounts of clay soils added, the Atterberg limits, namely the liquid
limit (LL), sticky point (SP), and plastic limit (PL), generally increase with
increasing amounts of clay soils added. The mechanical resistance declines when the
condition is moist. When dry, Grumusol increases mechanical resistance
substantially. The aggregate stability tends to decrease, even though there is a
tendency for the number of aggregates each with a diameter bigger than 2.0 mm to
increase. The response of the soil mixture to the Proctor standard compaction shows
that 10% to 40% mixture of Latosol or 10% to 50% of Grumusol brings about an
increase in dry soil bulk density. The maximum dry bulk density values of the
mixtures are achieved at different critical moisture contents.
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