Browsing by Author "Nandasena, M.A.G.H."

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    Effect of Biochar on Phosphorus Availability and Fixation in Selected Rubber (Hevea Brasiliensis) Growing Soils
    (Uva Wellassa University of Sri Lanka, 2013) Nandasena, M.A.G.H.
    In most rubber [Hevea brasiliensis (A. Juss.) Muell. Arg.] growing soils Phosphorus (P) availability is very low and added P fertilizers become unavailable to the rubber plant due to strong fixation of it into Fe and Al oxide minerals prevalent in these soils. Some studies have observed that amending soils with biochar, a co-product of thermochemical conversion of lignocellulosic materials into advanced biofuels, has increased the P uptake and cut down chemical P fertilizer usage in rubber nursery plants. Therefore, a laboratory incubation study was undertaken to determine the dynamics of soil P availability in three rubber growing soils from Parambe (PR), Thanamalwila (TW), and Payagala (PY) after amending them with three different biochar (BC) types made from Rubber wood (RW), Gliricidia (GL), and Paddy husk (PD). In P availability experiment, each soil type was amended with the 3 BC types at 3 different rates viz, 0, 2 and 5 by weight. The soil moisture content was maintained at 80% of water holding capacity (WHC) and P availability was determined at 0, 1, and 4 weeks after the incubation time period. Fixation capacity of soils amended with BC types and rates was assessed using the Portch and Hunter (1998) method. Available P contents were different among the three rubber growing soils and were in the order Thanamalwila < Parambe < Payagala. BC produced from Gliricidia BC had the highest amount of available P while Paddy husk BC had the lowest. After amending soils with BC, the available P increased in order of Thanamalwila soil < Payagala soil < Parambe soil. Among all soil types studied the Payagala soil had the lowest P fixation ability, and Parambe was the highest P fixing soil. Application of BC decreased the P fixation in Thanamalwila and Parambe soils but not in Payagala soils. The greatest decrease was observed with biochar produced from rubber wood and least decrease was With Paddy husk BC. BC can act as a source of P. Keywords: Biochar, Fixation, Hevea brasiliensis, Amendment, Incubation, Availability
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    Effect of Biochar on Phosphorus Availability and Fixation in Some Rubber Growing Soils of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2013) Nandasena, M.A.G.H.; Herath, H.M.S.K.; Dharmakeerthi, R.S.
    In most rubber growing soils in Sri Lanka, Phosphorus (P) availability is very low and added P fertilizer becomes unavailable to the rubber plant due to strong fixation into Fe and Al oxide minerals prevalent in these soils (Dissanayake et al., 1994). Biochar (BC) may significantly improve soil fertility in acid and highly weathered soils (Lehmann and Rondon, 2006). With respect to soil chemical fertility, Dharmakeerthi et al. (2012) observed a significantly high P uptake in some BC amended rubber growing soils. BC have high P concentration than in other organic materials (Brown 2009). However, no experiment has been so conducted so far on dynamics of soil P (availability and fixation) in BC amended rubber soils, both in Sri Lanka and other rubber growing countries. Therefore, objectives of the present study were: (i) to study the changes in P availability with time in three contrasting soil types in rubber growing areas when they were amended with rubber wood biochar (RWBC), and (b) to determine the effect of RWBC on P fixation in those soils. Methodology Two factorial experiments with two factors; three soil types and three BC rates were conducted under laboratory conditions at Rubber Research Institute of Sri Lanka. . Biochar was produced from rubber wood (RW) at 350°C and added in to the three soils: Reddish Brown Latasolic soil from Parambe (PR), Reddish Brown Earth soil from Thanamalwila (TW), and Red Yellow Podsolic soil from Payagala (PY). Three BC rates were 0, 2 and 5% (w/w) from RW BC. Soils and BC samples were characterized for some important chemical properties using standard methods. In the first experiment each soil type was amended with the 3 BC rates and incubated in four replicates at 80% of water holding capacity (WHC), for 4 weeks. Available P contents were measured at 0, 1, and 4 weeks after incubation. In the second experiment, P fixation capacity of the three soils amended with three different BC rates was assessed, in triplicate, using the Portch and Hunter (1998) method with slight modifications. Five ml solution containing 0, 20, 40, 60 and 80 ppm of P were added to BC amended and unamended soils after air-drying of 3-5 days. Available P from these two experiments were extracted according to the Bray II (Bray and Kurtz, 1945) method and determined by using a SKALAR San++auto analyzer. Data were analyzed using PROC GLM program of the SAS software package