Successive applications of fertilizers blended with biochar in the soil improve the availability of phosphorus and productivity of maize (Zea mays L.)

Abstract Potential shortages in the reserves of phosphorus (P) rock and low soil P availability are among the main limiting factors for agricultural development. Recent studies show that biochar plays a crucial role in regulating soil physicochemical properties and crop development. To further verify the contribution of biochar to availability of soil P and nutrient efficiency of crop P, a maize continuous cropping field trial was started in 2013 to investigate the effects of biochar (0 and 2.63 t ha−1) combined with P fertilizer (0 and 26 kg ha−1) on soil biologically-based P and maize P use efficiency and yield. The treatments included mineral NPK fertilizer (NPK), mineral NK fertilizer (NK), mineral NPK fertilizer in combination with biochar (NPK + BC) and mineral NK fertilizer in combination with biochar (NK + BC). The following results were obtained in 2017 and 2018: biochar increased the pH, electrical conductivity (EC), total C (TC) and total P (TP) of the soil. Biochar can increase soil biologically-based P (CaCl2-P, enzyme-P, citrate-P and HCl-P). The grain yield of the NPK + BC treatment reached the highest point and improved maize grain yield by 4.2 %–12.5 % compared with NPK fertilization alone. Moreover, the application of biochar (2.63 t ha−1) instead of phosphate fertilizer in these experimental conditions did not lead to a decrease in the yield of maize. The addition of biochar increased the contents and uptake of P in maize grains, while negatively affecting the content and uptake of P in maize stover. Increases in P fertilizer use efficiencies (PUE) (12.4 %–31.4 %) and agronomic P efficiencies (AEP) (21.6 %–51.2 %) occurred after the application of biochar. The yield of maize and PUE positively correlated with the soil biologically available P. The structural equation modeling (SEM) results suggest that the increases in maize yield could be ascribed to improvements in soil biologically-based P and soil properties. Therefore, the addition of biochar is an effective approach to enhance the yield of maize, which is not only relevant to the improvement of soil biologically-based P but also increases in P use efficiency.