Characteristics of magnesium rich synthetic gypsum and its effect as a secondary nutrient source for rubber seedlings on acid soils
Ultisols and Oxisols, the common soil in Malaysia, do not usually contain optimal levels of cations such as K, Ca and Mg, required in large amounts for crop growth and productivity. Thus, the management of input plays an important role in crop production in these widely occurring soils of Peninsu...
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Format: | Thesis |
Language: | English |
Published: |
2021
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Subjects: | |
Online Access: | http://psasir.upm.edu.my/id/eprint/104439/1/AROLU%20FATAI%20AYANDA%20-%20IR.pdf |
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Summary: | Ultisols and Oxisols, the common soil in Malaysia, do not usually contain optimal levels
of cations such as K, Ca and Mg, required in large amounts for crop growth and
productivity. Thus, the management of input plays an important role in crop production
in these widely occurring soils of Peninsular Malaysia. Rubber requires large amounts
of nutrients to sustain its growth and production so that faster growth and high latex yield
can be achieved and maintained. The use of fertilizer to supply nutrients for rubber is
essential in rubber cultivation; however, fertilizer costs account for a larger percentage
of production costs. As such, it is imperative to seek for a local alternative source that is
cost-effective. Recent studies on MRSG, a by-product obtained from industrial refining
of rare earth show that the material contains nutrient elements that may be beneficial for
rubber growth in addition to its high pH that ameliorate the impact of soil acidity
limitation on crop growth. Therefore, this research was conducted to study the
physicochemical characteristics of MRSG, its effect on acid soils, rubber growth, and
whether MRSG can be a secondary nutrient source for rubber plants at the growing
phase. The characterization results indicated that MRSG has valuable properties that can
promote its use in amending soil fertility constraints on nutrient-deficient tropical acid
soils. Incubation and leaching column studies were conducted to assess the effect of
MRSG on the chemical properties of Ultisol and Oxisol in Malaysia and model the
nutrient release pattern from the material over a 6-month period. The incubation
experiment was as a factorial experiment consisting of 2 soil types, 3 treatments and five
rates including control (0, 1, 2, 4 and 8) and laid out as a completely randomized design
(CRD). For the leaching experiment, the treatment consists of 1 t ha-1 of MRSG, GML
and kieserite with three replications arranged in a complete randomized design (CRD).
The study comprised two soil orders viz Ultisol and Oxisol belonging to the Bungor and
Segamat series based on Malaysian classification for local soils.
The amount of nutrients released into soil solution and present on the soil exchange site
due to the application of MRSG at various rates and months were fitted into different
functions using python programming script. The pattern of nutrient release from MRSG
was similar in the two studied soils and amounts of nutrient released increased with the
duration of the experiment. Nutrients release kinetics for all samples are adequately
described by the parabolic diffusion, power function and Elovich equations. The
intercept constants of the equations are strongly positively related to the ratio of nutrients
contained in MRSG. The models showed good performance (R2 value in range 0.9 to
0.99) in most samples tested except for the kieserite treatment group. The model indicates
that MRSG has a disintegration behavior similar to GML and can be used to achieve a
similar result in acid soil amelioration and soil nutrient enhancement. The leaching study
showed that MRSG is available in the soil system and can move beyond the zone of
incorporation into the sub-soil to further ameliorate subsoil acidity. The Ca and Mg ions
contained in MRSG are not easily leached out of the soil profile, thus MRSG can be a
potential substitute for lime (GML) on acid soils.
For nursery trial to understand the effect of MRSG application on the growth of immature
rubber, three-month-old rubber seedlings of the same size and/or height were obtained
from RISDA for planting on Ultisol and Oxisol. The experimental units consisted of four
rubber seedlings, with a total of 200 seedlings planted in the polybags. Treatments for
this study was based on using GML, kieserite and MRSG as fertilizer source to supply
the recommended Mg requirement for rubber seedlings in the nursery based on RISDA
formulation. Determination of growth parameters of the rubber seedlings was carried out
at 3 monthly intervals. The result of the experiment showed that incorporation of MRSG
increased the soil pH and decreased the aluminum content. MRSG application also
increased the level of available phosphorus and secondary nutrients such as calcium. The
growth of rubber seedlings in the glasshouse for the parameters of height, stem diameter,
root length and root surface area were significantly enhanced in the two studied soils
(Ultisol and Oxisol) by the addition of MRSG which gave a result comparable to other
sources of Mg fertilizer. It was observed that plant growth performance was better on the
Ultisol compared to the Oxisol. This study showed that the logistic growth curve model
in the form of y = A/ (1+be-ct), where y and t were the plant growth parameters and
months after transplanting, respectively, while A, b and c were regression constants were
biologically fitted in describing the growth in terms of each of the parameters (plant
height, stem girth and total plant biomass) versus months after transplanting. At each
treatment, the model had an F value with a high approximate probability level at a =
0.0001. In terms of the vegetative growth of the rubber seedlings, MRSG treatments gave
comparable results to that of GML and kieserite, thus, indicating the possibility of using
MRSG as a replacement of kieserite and GML as Mg source (Mg-fertilizer) to sustain
rubber seedling growth. |
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