Maize straw and its biochar affect phosphorus distribution in soil aggregates and are beneficial for improving phosphorus availability along the soil profile

Abstract

Return of crop straw and its biochar to the agricultural field decreases pressure on phosphorus (P) resources and reduces leaching and P runoff. We conducted a 5‐year field trial from 2013 to 2017 to study the capability of maize straw and its biochar to retain soil P, which was quantified by investigating the distribution of P fractions in the soil profile (0–100 cm) and soil aggregates of different grain sizes. The impact of soil treatments with nitrogen‐phosphorus‐potassium (NPK) fertiliser alone or combined with biochar or maize straw were examined. We found that maize straw and its biochar increased soil aggregate stability, which showed an increase in mean weight diameter, geometric mean diameter, and aggregates with diameter > 250 μm. Maize straw and its biochar promoted both inorganic (dicalcium phosphate dehydrate [Ca2‐P], octocalcium phosphate [Ca8‐P], aluminium phosphate [Al‐P], iron phosphate [Fe‐P], hydroxyapatite [Ca10‐P], and occluded phosphate [O‐P]) and organic (labile organic phosphorus, LOP, and moderately labile organic phosphorus, MLOP) P accumulation and stabilization in soil aggregates, especially in small macroaggregates of 250–2000 μm. Total phosphorus (TP), Ca8‐P, Fe‐P, LOP, MLOP, moderately resistant organic phosphorus (MROP) and highly resistant organic phosphorus (HROP) were enhanced by maize straw and its biochar, whereas Ca2‐P and O‐P were decreased in the 0–20‐cm topsoil. We measured decreased TP, Fe‐P, O‐P and Ca10‐P in the 40–100‐cm soil layer following maize straw and biochar deposition, whereas higher Ca2‐P, Al‐P, MROP and HROP were obtained in maize straw‐supplemented soil relative to NPK fertiliser treatment in the 20–100‐cm soil layer. Thus, maize straw and its biochar can be used to effectively improve soil structure to support P retention and biochar has the potential to reduce P leaching from the soil profile. Highlights Maize straw and its biochar effectively improved soil structure to support P retention Inorganic and organic P fractions mainly accumulated in the small macroaggregate fraction Biochar has the potential to reduce P leaching in the soil profile

The distribution of phosphorus from recycled fertilizers to different soil fractions determines the phosphorus availability in soil

“…Previous studies have shown that the level of soil available P remains stable following cattle manure application (Mkhonza et al, 2020), but was found decreased when mineral P fertiliser was used (Braos et al, 2020). Some studies suggest that long-term straw retention in the soil improves the content of soil available P Cao et al, 2021). However, in our study, incorporation of maize straw in the soil did not improve soil P availability in both soils.…”

Effects of Biochar on the Microenvironment of Saline-Sodic Soil and Maize Growth

“…Gemmatimonadetes is a phylum of biocontrol bacteria and plant growth-promoting bacteria in soils. Some researchers have suggested that the abundance of Gemmatimonadetes is closely related to phosphorus metabolism [18]. In the present study, we found that the significant increase in AP in biochar-treated soil may be induced by the increase in Gemmatimonadetes abundance.…”

Machine learning and computational chemistry to improve biochar fertilizers: a review

“…Ash had a higher phosphorus content than cow manure because the combustion process removed volatile matters and reduced the material mass. Similarly, the total phosphorus content in maize stover is 3.43 g/kg, which is lower than the biochar produced from biomass by 5.44 g/kg (Cao et al 2021). The result indicates the positive effect of pyrolysis at 500 °C for 2 h on the total phosphorus concentration of the lignocellulosic material due to the mass loss via volatilization.…”