Can biochar increase the bioavailability of phosphorus?

Abstract

A large proportion of phosphate (P) fertilizer applied to Andosols reacts with reactive aluminum (Al) and iron (Fe) to become unavailable for plant uptake. We investigated whether biochar could enhance plant growth by (i) mobilizing soil P through changing soil pH or facilitating the growth of arbuscular mycorrhizal fungi (AMF), and/or (ii) introducing additional P. We grew Lotus pedunculatus cv barsille in two Andosols of contrasting P status amended with three biochars (with distinct porosity, nutrient and liming properties) at a dose of 10 t ha-1 for 32 weeks. The growth medium was divided into a root and a hyphal zone through a nylon mesh and a tephra layer that allowed the P in the hyphal zone to be transferred only by AMF hyphae. The addition of a relative nutrient-rich biochar (e.g. made from willow woodchips) with liming properties to the root zone of the P-deficient soil increased plant growth by 59% and P uptake by 73%. Pine-based biochar provided no extra nutrient acquisition and no plant-growth stimulation when added to the root zone of the Pdeficient soil. However, when hyphae of those plants had access to a P-rich soil patch, the presence of pine biochar in the soil patch greatly enhanced P uptake and plant growth (e.g., by 76% and 40% when using biochar produced at 450 o C compared to the absence of it). None of the tested biochars conferred advantages in the root zone of a high-P soil. We concluded that the benefits from biochar addition to nutrient uptake and plant growth are biochar-and soil-specific. Thus, biochars need to be tailored-made for certain soils by optimizing feedstock and pyrolysis conditions before application.

Effects of biochar on nutrients and the microbial community structure of tobacco-planting soils

“…And there is no consistent conclusion about the effect of biochar on soil available P, though biochar contains a large amount of phosphorus with high effectiveness (Enders et al, 2012;Shen et al, 2016). However, phosphorus adsorption and desorption in soil can also be influenced by the biochar additions and soil types.…”

Effects of biochar application on nitrogen leaching, ammonia volatilization and nitrogen use efficiency in two distinct soils

“…The increased ryegrass growth could also be attributed to the promoted ryegrass N adsorption by biochar. Based on our data (Table 2 and Table 3), the total N uptake and were not available in otherwise poor soils (Shen et al, 2016;van Zwieten et al, 2010a). For specific nutrients, soil N might be mineralized into inorganic N when N supplementation is not sufficient for plant use or when the demand for biochar induces microbial activity (Nelissen et al, 2012;Muhammad et al, 2016).…”

“…The application of biochar to agricultural soil is a potential way of increasing nutrient bioavailability and decreasing nutrient leaching from soil (Shen et al, 2016;Lehmann et al, 2003). Many studies have reported that biochar incorporation could reduce inorganic N leaching and increase N retention in the soil (Major et al, 2012;Sun et al, 2017;Yao et al, 2012).…”

Biochar effects on nitrogen and phosphorus use efficiencies of zucchini plants grown in a calcareous sandy soil

“…Biochar improves physical properties of soil, such as water holding capacity and soil aggregation (Obia et al, 2016;Curaqueo et al, 2014). It also recovers soil chemical properties such it increases the soil cation exchange capacity (Mohamed et al, 2016), thus increases nutrients against leaching and makes some of them more available to plants e.g., N, P and K (Amin, 2016;Gao et al, 2016;Muhammad et al, 2016;Shen et al, 2016). Hence, the biochar can be used as a substitute for phosphate fertilizers when reclaiming calcareous sandy soils because of its high content of P (0.6 to 3.2 g kg -1 ) that amount depends on the type of plant residues (Shenbagavalli and Mahimairaja, 2012).…”