Changing the Phosphate Regime of Soils in the Middle Taiga When Using Biochar

Abstract

The influence of wood biochar on the content of various forms of phosphates was studied in laboratory experiments on soils with different phosphorus availability. Soils of the middle taiga subzone of Karelia were used in this work: a sandy Umbric Podzol and a heavy loamy Umbric Retisol. The tests studied the effect of two fractions of biochar (3–5 and ≤2 mm) in an amount of 2% and 5% of soil mass on pHKCl, the content of available and total phosphorus, the inorganic phosphorus fractions (Chang-Jackson method), and the total phosphatase activity of soils, as well as the effect of separate and combined application of biochar and fertilizer (NPK) on the content of available phosphorus in a pot experiment with spring barley. The research revealed that biochar significantly increased the content of available phosphorus by 20–40%, increased the content of the fraction of Ca-bounded P, Al-bounded P and loosely-bounded P, and also increased the phosphatase activity in the Umbric Podzol. In pot experiment was noted a higher content of P2O5 in variants with biochar ≤2 mm, in variants with fertilizer, and a significant mutual influence factors of biochar and fertilizer. Biochar increased the content of available phosphorus by 2–6%, increased the content of Ca-bounded P and loosely-bounded P (with biochar ≤2 mm at 5% dosage), and had no significant effect on the phosphatase activity in the Umbric Retisol. Only combination of biochar ≤2 mm and fertilizer had a significant effect in pot experiment with Umbric Retisol. In general, the most noticeable effect on almost all studied indicators was provided by ≤2 mm fraction of biochar in a 5% dosage. The use of biochar led to statistically significant increase in pHKCl values, and did not affect the content of total phosphorus in both soils. Biochar had a greater effect on the phosphate regime of coarse-textured soil with an initially lower pH and a less content of available and total phosphorus.