The novel composting method has the ability to modify the
morphology of the clay structure in SBE, in remedying and improving other chemical attributes besides eliminating the acidic and
hydrophobic nature of the earth. The resulting SBE has been
transformed into an effective bio organic material with improved
organic carbon (OC) content from 7.1 to 16.5%, the CEC from 8.0 to
33.8 cmol/kg, the water-holding capacity from 6.1 to 16.5 ml/100 g
and the C:N ratio from 290 to 9–21. The OC increased due to the
residual oil in SBE and the high OC content of the co-composted
materials. Most of the degradable organic matter was decomposed
and replenished. An increase in OC after composting would have
contributed to the observed increase in CEC, thereby enhancing the
nutrient supplying capacity of the bio organic fertilizer made. Surprisingly, the C:N ratio improved tremendously after composting.
This showed that the microorganisms present in SBE, 8000 colonial
form unit (CFU) in 10 mL of diluted SBE supernatant, had utilized
the residual oil and the organic matter readily available in SBE as
carbon source to manipulate and transform SBE into a suitable base
material facilitating microbial activities.
When SBE is associated with soil,the CEC of soil will be improved
(Table 4) by weakly binding the exchangeable cations onto the
negatively charged soil surface via electrostatic forces. The CEC
of the mineral soil mixed with composted SBE at SBE:soil ratio of
50:50 has increased from its original 8 cmol per kg to 32–39 cmol
per kg. This is indicative of an increase in organic matter (source
of negative electrostatic sites), thus an increase in ability of thesoil to exchange, attract and retain nutrient elements from SBE
in a loosely bound bonding. This will prevent nutrient loss via
leaching by allowing plants to extract them from the soil via ‘swapping’ them with H+.
The high CEC is also indicative of greater water-holding capacity
and slow release of water/nutrients once it is mixed and activated with soil. It holds 20 mL of water per 100 g of SBE while
soil mixed with composted SBE (50:50) can hold up to 140 mL of
water (Table 4). The resulting bio organic material thus has a slow
release property in managing the controlled-released efficiency of
nutrients and water in soil–fertilizer interaction. This is because the
transformed SBE tends to entrap/encapsulate volatile nutrient elements (such as N) and then releases them slowly into the soil it is
applied to. An optimal C:N ratio ranged 9–21 in SBE-formulated bio
organic fertilizer was achieved approaching C:N ratio for adequate
microbial soil function, thus shows evident that it contributes toplant nutrition when applied to the soil, and that it is superior to
other commercial organic fertilizers (Fig. 1) in terms of biological
decomposition of organic residue and bioavailability of C, N and P.
The SBE-based bio organic fertilizer is favourably pelletized to
give good binding effect to the fertilizer due to the presence of
“natural binder” vis-à-vis the residual oil in SBE.
The novel composting method has the ability to modify themorphology of the clay structure in SBE, in remedying and improving other chemical attributes besides eliminating the acidic andhydrophobic nature of the earth. The resulting SBE has beentransformed into an effective bio organic material with improvedorganic carbon (OC) content from 7.1 to 16.5%, the CEC from 8.0 to33.8 cmol/kg, the water-holding capacity from 6.1 to 16.5 ml/100 gand the C:N ratio from 290 to 9–21. The OC increased due to theresidual oil in SBE and the high OC content of the co-compostedmaterials. Most of the degradable organic matter was decomposedand replenished. An increase in OC after composting would havecontributed to the observed increase in CEC, thereby enhancing thenutrient supplying capacity of the bio organic fertilizer made. Surprisingly, the C:N ratio improved tremendously after composting.This showed that the microorganisms present in SBE, 8000 colonialform unit (CFU) in 10 mL of diluted SBE supernatant, had utilizedthe residual oil and the organic matter readily available in SBE ascarbon source to manipulate and transform SBE into a suitable basematerial facilitating microbial activities.When SBE is associated with soil,the CEC of soil will be improved(Table 4) by weakly binding the exchangeable cations onto thenegatively charged soil surface via electrostatic forces. The CECof the mineral soil mixed with composted SBE at SBE:soil ratio of50:50 has increased from its original 8 cmol per kg to 32–39 cmolper kg. This is indicative of an increase in organic matter (sourceof negative electrostatic sites), thus an increase in ability of thesoil to exchange, attract and retain nutrient elements from SBEin a loosely bound bonding. This will prevent nutrient loss vialeaching by allowing plants to extract them from the soil via ‘swapping’ them with H+.The high CEC is also indicative of greater water-holding capacityand slow release of water/nutrients once it is mixed and activated with soil. It holds 20 mL of water per 100 g of SBE whilesoil mixed with composted SBE (50:50) can hold up to 140 mL ofwater (Table 4). The resulting bio organic material thus has a slowrelease property in managing the controlled-released efficiency ofnutrients and water in soil–fertilizer interaction. This is because thetransformed SBE tends to entrap/encapsulate volatile nutrient elements (such as N) and then releases them slowly into the soil it isapplied to. An optimal C:N ratio ranged 9–21 in SBE-formulated bioorganic fertilizer was achieved approaching C:N ratio for adequatemicrobial soil function, thus shows evident that it contributes toplant nutrition when applied to the soil, and that it is superior toother commercial organic fertilizers (Fig. 1) in terms of biologicaldecomposition of organic residue and bioavailability of C, N and P.The SBE-based bio organic fertilizer is favourably pelletized togive good binding effect to the fertilizer due to the presence of“natural binder” vis-à-vis the residual oil in SBE.
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