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Application of Biochar and Fate of Soil Nutrients

K. T. Khan
Bangladesh-Australia Centre for Environmental Research, Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

M. T. A. Chowdhury
Bangladesh-Australia Centre for Environmental Research, Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

S. M. Imamul Huq
Bangladesh-Australia Centre for Environmental Research, Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

An in vitro incubation study was conducted with soil having seven applications of different treatments of biomass and biochar including a control. The biochar and biomass were applied at a rate of 5 t/h a and incubated at field moisture condition for 30, 60 and 90 days individually in different pots. Total organic carbon (C), total nitrogen, phytoavailable nitrogen (N), phosphorus (P), sulfur (S) and potassium (K) were determined at the end of each incubation period. Total soil organic carbon (SOC), showed a substantial declining trend in all the soils - more prominent in the biochar treated soils than its corresponding biomass treated soils. The pH, total N, phytoavailable N, P, K were substantially higher in the biochar treated soils irrespective of the incubation days compared to the biomass treated soils. Conversely, the available S contents of the biochar treated soils were lower than that of biomass treated soils. The effect of biochar on these nutrients vis-à-vis soil health is discussed.

Keywords: Soil nutrients, Biochar, Soil health

Location: The vegetable fields in Jagir Dighulia village, Atigram union, Manikganj sadar, Manikganj District, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Biochar, Soil fertility

Objectives:

The present work has been carried out with following objectives in mind – the nutrient release after application of equal rate of biomasses and their corresponding biochars in soil.

Methodology:

Soil sampling site: Surface soil (0 - 15 cm) was collected from vegetable fields in Jagir Dighulia village, Atigram union, Manikganj sadar, Manikganj District. The geo-location of the sampling site is 23°51.884 N and 90°06.219 E. The soil is a non calcareous grey floodplain belonging to the Melandaha series. Sample collection and preparation: The collected soil samples were dried in air 4 to 5 days by spreading in a thin layer on a clean piece of brown paper after being transported to the laboratory. Visible roots and debris were removed from the sample and discarded. To hasten the drying process, the samples were exposed to sunlight. After air-drying, a portion of the sample containing the larger aggregates was ground by gently crushing with a wooden hammer. Ground samples were passed through a 2 mm stainless steel sieve. The sieved samples were then mixed thoroughly and stored in labeled plastic containers until required for various physical analyses. Another portion of the soil samples (2 mm sieved) were further ground and passed through a 0.5 mm sieve. The sieved samples were mixed thoroughly and stored as above until required for chemical and physico-chemical analyses. The bulk soil samples collected for incubation study were air-dried, cleared of debris and crushed to reduce the size of large clods. The crushed soil samples were screened through a 5 mm sieve. Biochar and biomass sample preparation: Three different types of biomasses, i.e. rice husk, rice straw and saw dust were procured locally. The biomasses were properly dried in oven at ~80o C (Only rice straw was washed and dried and then ground). Then, a portion of these biomasses were sieved through a 0.25 mm sieve for routine analyses. Another portion was kept to produce biochar (Mahmud et al. 2014). Rest of the portion was stored for incubation study. After making biochars from each of the biomasses they were sieved through a 0.25 mm sieve. This 0.25 mm sieved biochars were stored for routine analyses. Rest of the samples was stored for incubation study. In vitro incubation experiment: In order to study the fate of soil nutrients as affected by the application of biochar, an in vitro incubation experiment was performed using seven different treatments. The total incubation period was 90 days portioned into three intervals, viz., 30, 60 and 90 days. So, a total number of 21 pots were used in the incubation study. Pot preparation: Half kilogram sized plastic pots were procured from local market. These were washed properly with water and dried at ambient temperature of the laboratory and stored. Each pot was marked in accordance with the treatments. Then, 400 g of air dried 5 mm sieved soil sample were taken into each of the plastic pots and 1 g each of either biomass or biochar was thoroughly mixed with the soil. The soils were then incubated at field moisture condition for 30, 60 and 90 days, respectively. Collection of sample at the end of each incubation: After incubation, the soil in each of the pots was mixed thoroughly for ensuring uniform sampling. Thereafter, the soil samples from each of the pots were collected randomly for further analyses. Laboratory analyses: Various physical, chemical and physico-chemical properties of the soil as well as the biochar and biomass were analyzed in the laboratory. The particle size analysis of the soil sample was done by Hydrometer method (Huq and Alam 2005). pH of soil (pre- and post-experiment) and of biochar and biomass were determined by using a pH meter at a soil : water ratio of 1 : 2.5 for soil and a ratio of 1 : 15 for biochars and biomasses. Organic carbon of the soil (pre- and post-experiment) and of biochar and biomasses were determined by wet oxidation method of Walkley and black as described in Huq and Alam (2005). Total nitrogen of the samples was determined by steam distillation of the Kjeldahl digest (Jackson 1962). Available nitrogen was determined by extracting samples with 1M KCl and then extracts were distilled with 40% NaOH which gave off ammonia that were collected on a 2% boric acid-mixed indicator solution. The distillate was titrated against 0.02M sulfuric acid (H₂SO₄) as described in Huq and Alam (2005). The available phosphorus of the samples were determined by extracting samples using Bray and Kurtz method (for pH < 6.0) and Olsen method (for pH > 6.0) and then the extracts were used to estimate P colorimetrically by following the blue color method using ascorbic acid by spectrophotometer at 880 nm. The available S was determined by extracting the samples with calcium dihydrogen phosphate monohydrate [Ca(H₂PO₄)₂. H₂O] and then the extracts were analyzed with a spectrophotometer at 420 nm. The available K of the samples was determined by a flame analyzer after extracting the soil samples (pre- and post-experiment) with 1M ammonium acetate at pH 7.0. Total P content of the soil and biomass and biochar samples were determined colorimetrically using a spectrophotometer at 490 nm by developing yellow color with vanadomolybdate after the extract was collected by digesting with ternary acid mixture (Huq and Alam 2005). Total potassium content of the soil, biomass and biochar samples were determined by a flame analyzer after digesting the samples with ternary acid mixture. Total sulphur content was determined turbidimetrically by a spectrophotometer at 420 nm after digesting the samples with IM HCl. Data analysis: All data were statistically analyzed by using Microsoft Excel 2010 and/or MINITAB (Version 16.2).

Source of Information: Bangladesh J. Sci. Res. 27(1): 11-25, 2014 (June)

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In conclusion, it can be said that as is found in different literatures about the effect of biochars on soil health, the phenomenon is not conclusive, rather diverse which is also apparent in the present study. The carbon sequestration by biochar needs to be further studied vis-à-vis soil nutrients.

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