pH effects of the addition of three biochars to acidic Indonesian mineral soils

Abstract

Soil acidity may severely reduce crop production. Biochar (BC) may increase soil pH and cation exchange capacity (CEC) but reported effects differ substantially. In a systematic approach, using a standardized protocol on a uniquely large number set of 31 acidic soils, we quantified the effect of increasing amounts (0-30%; weight: weight) of three types of field-produced BCs (from cacao (Theobroma cacao. L.) shell, oil palm (Elaeis guineensis. Jacq.) shell and rice (Oryza sativa. L.) husk) on soil pH and CEC. Soils were sampled from croplands at Java, Sumatra and Kalimantan, Indonesia. All BCs caused a significant increase in mean soil pH with a stronger response and a greater maximum increase for the cacao shell BC addition, due to a greater acid neutralizing capacity (ANC) and larger amounts of extractable base cations. At 1% BC addition, corresponding to about 30 tons ha −1 , the estimated increase in soil pH from the initial mean pH of 4.7 was about 0.5 units for the cacao shell BC, whereas this was only 0.05 and 0.04 units for the oil palm shell and rice husk BC, respectively. Besides depending on BC type, the increase in soil pH upon the addition of each of the three BCs was mainly dependent on soil CEC (low CEC resulting in stronger pH increase), and to a lesser extent on initial soil pH (higher initial pH resulting in stronger pH increase). Addition of BC also increased the amount of exchangeable base cations (cacao shell ) oil palm and rice husk) and CEC. Through this systematic screening of the effect of BC on pH and CEC of acidic soils, we show that a small addition of BC, in particular if made of cacao shell, to acidic agricultural soils increases soil pH and CEC. However, the response is highly dependent on the type, quality and amount of the added BC as well as on intrinsic soil properties, mainly CEC.

Cation exchange capacity of biochar: An urgent method modification

“…This was the reason for setting 0.2 mS cm -1 as EC threshold in the pretreatment. Previous research (Martinsen et al, 2015) using a sub sample of the same cacao shell biochar showed that CEC-BC without any pretreatment was 197 cmol(+)/Kg, while in our experiment this was 59.1 cmol(+) Kg -1 with pretreatment. Furthermore, Graber et al (2017) found significant differences between CEC-BC and CEC-NH4 + for some of the biochars they analyzed.…”

“…Biochar is a carbon-rich product made by pyrolysis of organic waste, which may be used as a soil enhancer. Particularly, in tropical soils biochar has been shown to have a positive impact on soil fertility, including increased potassium (K + ) content, pH, water retention capacity, and cation exchange capacity (Jeffery et al, 2011;Liang et al, 2006;Martinsen et al, 2015), which all contribute to increased crop yield (Jeffery et al, 2017). Moreover, biochar is emerging as an alternative for heavy metal remediation in soil and water (Ahmad et al, 2014).…”

Impact of biochar properties on soil conditions and agricultural sustainability: A review

“…The biochars produced at lower‐temperature may probably possess more organic functional groups of COOH and C‐OH and subsequently increasing nutrient retention sites compared to high‐temperature biochars (Ippolito et al, ). The increase in the pH of biochar‐amended soils could be due to (a) the alkalinity of biochar produced from high‐temperature pyrolysis (Martisen, Alling, Nurida, et al, ); (b) the formation of negatively charged carboxyl, hydroxyl, and phenolic functional groups on the surface of biochar material, which reduces the H + concentration in soil solutions (Wang et al, ); and (c) the presence of carbonates, silicates, ash contents, and bicarbonates that bind H + from soil solution (Martisen et al, ; Wang et al, ). Generally, the amelioration effects of biochar addition to soils are mainly dependent on both the feedstock type and the processing temperature (Abbasi & Anwar, ; Usman et al, ).…”

Biochar‐Based Fertilization with Liquid Nutrient Enrichment: 21 Field Trials Covering 13 Crop Species in Nepal

“…While until now positive yield responses to biochar applications have almost exclusively been obtained on poor and degraded soils (Biederman & Harpole, 2013;Cornelissen et al, 2013), all soils of the present biochar field trials can be considered as relatively fertile with their SOM contents ranging from 2·3 to 9·2% and soil pH values ranging from 4·5 to 6·1 with two exceptions at 4·1 and 3·8. Several authors showed that biochar may have a liming effect which depends on biochar and soil type (Silber et al, 2010;Butnan et al, 2015;Camps-Arbestain et al, 2015;Jeffery et al, 2015;Martinsen et al, 2015). Moreover, Jeffery et al (2015) showed in his meta-analysis a clear dependency of biochar-caused yield increases on the initial soil pH.…”