Abstract
PurposeThis study aimed to assess the impact of two biochars applied at the rate of 15 t ha−1 on physico-chemical parameters of an oxisol in Cameroon.MethodsThe biochars were made from slow pyrolysis (~ 300 °C, 4 h) of eucalyptus tree bark and corncobs and then incorporated into the top 15 cm of the soil with or without straw. The soil tillage mode was either flat plots or furrows and ridges. Soil porosity, bulk density, saturated hydraulic conductivity, available water content, pH, nitrogen, potassium, phosphorus, cation exchange capacity and electrical conductivity were analysed before biochar application, then 6 and 12 months after.ResultsNone of the measured soil physical parameters were affected by the presence or type of biochar. The total porosity was lower during the second production period compared to the first, while available water content and van Genuchten parameters increased during the second production period. No significant difference was observed between soil nitrogen, phosphorus, potassium, cation exchange capacity and electrical conductivity of control and treated plots.ConclusionWe recommend that straw be pyrolysed and the resulting biochar incorporated into soil instead of burying straw (as is actually done in furrow and ridges tillage mode).
Highlights
Biochar is the porous carbonaceous solid produced by pyrolysis, i.e. thermochemical conversion of organic materials in an oxygen-depleted atmosphere
Flat plots (FP) had lower ρa compared to furrows and ridges (FR) and ρa decreased during the second production period; all these are due to soil mixing from one production period to another
The authors meta-analysis reported that soil porosity was not significantly affected by addition of biochar in highly porous soils and at low and medium application rates (3.5–4% which is equivalent to 23–36 kg ha−1 based on our biochar bulk density and assuming incorporation at 20 cm depth)
Summary
Biochar is the porous carbonaceous solid produced by pyrolysis, i.e. thermochemical conversion of organic materials in an oxygen-depleted atmosphere. Biochars made from diverse biomass are characterized by different morphological and physico-chemical properties, and differ based on. In tropical areas such as in Cameroon, oxisols are among the dominant soil types. Benefits only last for a few growing seasons, since added nutrients are prone to leaching, given the low CEC of oxisols (Baligar and Bennett 1986). In these acidic soils, biochar has been shown to improve the holding capacity of nutrients, including: phosphorus (P), calcium (Ca),
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