Nonadditive effects of biochar amendments on soil phosphorus fractions in two contrasting soils

Abstract

Increased soil total phosphorus (P) or available P has been reported in biochar‐amended soils, although the underlying mechanisms need to be fully understood. In the present study, two contrasting soils (acidic Haplic Luvisol and alkaline Calcaric‐Fluvisol) amended with wheat straw biochar were sequentially extracted with modified Hedley method to study the P transformation in the soils. Our results showed that biochar application significantly increased (positive effects) P fractions (except for NaHCO3‐Pi and residual‐P) content in Haplic Luvisol. The increased soil microbial activity and reduced soil acidity or increased cation exchange capacity may be accounted for enhanced P transformation. The reduced NaHCO3‐Pi content may be related to P immobilization with increased soil microbial activity induced by biochar addition because the high C:P ratios of biochar (ranged from 234 to 357) suggested net P immobilization occurred when biochar was incorporated into soil. Biochar application first (4 days) increased soil NaHCO3‐Po content and then decreased it with longer incubation time (30 days). The decrease in NaHCO3‐Po suggested that the labile organic P was converted into nonlabile inorganic or organic P. In comparison with those in Haplic Luvisol, almost all P fractions showed negative effects with biochar addition into Calcaric‐Fluvisol. The results may be caused by the P precipitation or sorption with increased soil pH with biochar application. On the basis of P transformation, biochar is recommended to be used in Haplic Luvisol (acidic soil) and not to Calcaric‐Fluvisol (alkaline soil) because of the positive effects and negative effects observed on P fractions in biochar‐amended soils.

Role of biochar in promoting circular economy in the agriculture sector. Part 1: A review of the biochar roles in soil N, P and K cycles

“…In contrast to the positive impact on soil-available P described previously, especially in acidic soils, it has been shown that biochar with low P content can reduce P availability in soils [72], through increasing P sorption capacity promoted by surface area increase [81] and in metal oxides and carbonates [82] derived from biochar, through immobilisation of P by stimulating microbial activity [80,83] and by means of precipitation of stable phosphate minerals in alkaline soils [65].…”

“…Thus, soil P fixation increases in alkaline soils amended with biochar through precipitation of Ca-P minerals and P sorption onto calcite in alkaline soils due to additional input of alkaline elements such as Ca, which is often contained in biochar [63]. In general, biochar had no effect on P sorption isotherms in alkaline soils, especially in soils with high P sorption capacity [63,80].…”

Association of biochar properties with changes in soil bacterial, fungal and fauna communities and nutrient cycling processes

“…Biochar decreased the activity of acid phosphomonoesterase but increased the activities of alkaline phosphomonoesterase (responsible for mineralization of organic P), indicating that biochar may affect related microorganisms and their released enzymes by increasing soil pH (Jin et al 2016). Xu et al (2018a) showed that biochar application significantly increased fractions of H 2 O-soluble and NaOH-extractable inorganic P, and NaHCO 3 -extractable organic P, but decreased the NaHCO 3 -extractable inorganic P fraction. This indicated that biochar addition assists microorganisms to solubilize the fixed P and increases microbial P immobilization.…”

Towards sustainable agriculture for the salt‐affected soil

“…A better method is to apply organic amendments to raise organic matter amount of the salt‐affected soil (Montiel‐Rozas, Panettieri, Madejón, & Madejón, ; Oo, Iwai, & Saenjan, ; Reed, Chadwick, Hill, & Jones, ; Veneklaas et al, ). Different types of organic amendments such as green manures, farmyard and poultry manures, compost, food‐processing wastes, and biochar have been applied to soils for enhancing soil quality (Bhaduri et al, ; Liu et al, ; Xu, Zhang, Shao, & Sun, ; Yang, Bian, Tang, Zhou, & Li, ). Among these, green manure is a promising way with long‐term effects and low cost (Bai et al, ; Bai, Xu, et al, ; Bai, Yan, et al, ; Bai, Zou, et al, ; Li et al, ; Maltas, Kebli, Oberholzer, Weisskopf, & Sinaj, ; Meier et al, ; Xu et al, ; Yang et al, ).…”