Effect of Biochar Application on pH and pH Buffering Capacity of Rubber Growing Soils
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Date
2013
Journal Title
Journal ISSN
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
Rubber (Heveabrasiliensis L.Muell. Arg.) growing soils in Sri Lanka are less fertile and
characterized by low cation exchange capacity (CEC), very high acidity, and low organic
carbon (OC). This has resulted low fertilizer use efficiency and low productivity in rubber
growing soils. In order to increase soil fertility effectively, amending these soils with biochar
(BC) are being evaluated (Dharmakeerthi et al., 2012). Biochar, is a solid material produced
from pyrolysis of biomass, is a highly alkaline material with high CEC and higher percentage of
stable OC (Sohi et al., 2010). Amending soils with BC may change soil pH and pH buffering
capacities (Xu et al., 2012). However, there is no data available on changes of soil pH after BC
addition in rubber growing soils not only in Sri Lanka, but also anywhere else in the world.
Therefore, this study was conducted to investigate the effect of rubberwood BC on pH and pH
buffering capacity of some contrasting rubber growing soilsin Sri Lanka.
Methodology
Two soils from traditional rubber growing areas i.e. Red Yellow Podsol (RYP) from Paiyagala
Estate, Dodangoda, Reddish Brown Latasol (RBL) from Parambe Estate, Parambe, and one soil
from dry zone, Reddish Brown Earth (RBE) from Thanamalwila ,representing contrasting agro -
ecological conditions were selected for the study. Those soils were mixed with BC made from
rubber wood with two different rates, 0 and 2% by weight andincubated at 70% water holding
capacity at room temperature 25±2ºC for 12 weeks. The change in pH was measured at 0, 1, 4,
and 12 weeks after the biochar amendment. pH buffering capacity was measured in another set
of amended soils, incubated for 40 days as above, using the methods given by Liyanage et al.
(2012) with certain modifications. All treatments were replicated four times.
Results and Discussion
Application of biochar increased pH in all three soils; the increase was very small in
Thanamalwila soil while the greatest observed in Payagala soil. Week after incubation, the pH
increase in the three soils were 0.4, 0.9 and 0.9 for Tanamalwila, Parambe and Payagala soils,
respectively (Figure 1). As incubation time increased from 1 to 12 weeks, the pH did not
increase significantly (p<0.05) in Thanamalwila and Payagala soils, and the gap decreased in
significantly (p<0.05) Parambe soils.
types.
Thanamalwila soil had the highest pH buffer capacity (7.3mmol/kgpH) while Payagala soil had
the lowest value (4.7mmol/kgpH) Parambe soil had (5.5mmol/kgpH) in between value. The pH
buffering capacity was highly significantly correlated with CEC of the soils ( R =0.92 ,p<
0.001), indicating that CEC was an important factor determining soil pH buffering capacity.
Description
Keywords
Agriculture, Export Agriculture, Crop Production, Rubber Production, Rubber Technology, Soil Science