Biochar to improve soil fertility. A review

Abstract

Soil mineral depletion is a major issue due mainly to soil erosion and nutrient leaching. The addition of biochar is a solution because biochar has been shown to improve soil fertility, to promote plant growth, to increase crop yield, and to reduce contaminations. We review here biochar potential to improve soil fertility. The main properties of biochar are the following: high surface area with many functional groups, high nutrient content, and slow-release fertilizer. We discuss the influence of feedstock, pyrolysis temperature, pH, application rates, and soil types. We review the mechanisms ruling the adsorption of nutrients by biochar.

Adsorption Characteristics of Ammonium Nitrogen and Plant Responses to Biochar Pellet

“…Similar results of adsorption using biochar and adsorbents for NH 4 -N have been described for ion-exchange resins [19], zeolites [20], and activated carbon [21]. This result implies that the biochar pellet can play an important role as an absorbent of NH 4 -N when applied in cropland.…”

“…The corresponding isotherm parameters are presented in Table 5. It was observed that the Langmuir adsorption capacity of the biochar pellet for NH 4 -N was 2.94 mg g −1 . Table 4 shows the amount of NH 4 -N adsorbed at equilibrium (q e ) at the slope and intercept, rate constants (K 1 and K 2 ) of the kinetic models.…”

“…For the adsorption rate of NH 4 -N to biochar pellet, the NH 4 -N concentrations from different masses of pig manure composts and retention times (6-336 h) were calculated from desorption models of NH 4 -N in the pig manure compost ( Table 2). On the basis of the data from a batch scale experiment, estimated releasing models of NH 4 -N in the different loading ratios of pig manure composts (0.1-1.5 g) were derived. From these equations, the released amount of NH 4 -N from each mass of pig manure compost could be calculated, and then these equations were used for normalizing the NH 4 -N contents in different ratios of biochar pellet to determine the releasing NH 4 -N concentrations from biochar pellets with different retention times.…”

“…The releasing patterns of NH 4 -N in deionized water of biochar pellets consisting of different ratios of biochar/pig manure were investigated. As shown in Figure 1, the concentration of NH 4 -N increased gradually in the combination of pellet mixed with biochar, as the retention time increased.…”

“…Biochar from thermal conversion technology has recently attracted attention for its potential ability of carbon sequestration, suggesting the possibility to act against climate changes through the addition of biochar into soil. Biochar's positive effects on the agro-ecosystem have been suggested to derive either from nutrients in the biochar or from its ability to control these nutrients [4]. When biochar is applied to soil, an additional application of fertilizer is still needed to increase crop yield.…”