Quantitative response of wheat yield and soil properties to biochar amendment in China

Objective Biochar, as a new type of soil remediation material, have been reported for the effects on crop yields. Quantitative assessment of their effects on wheat yield and soil properties are significant for the application of biochar in wheat production. Methods through searching China National Knowledge Infrastructure (CNKI), Web of Science and VIP literature database by key words of “biochar” and “wheat”, we collected 59 related trials and 227 sets of data published at home and abroad. Meta-analysis was used to quantitatively analyze the effects of biochar application on wheat yield and soil properties under different field management measures, soil conditions and biochars.

Results The average yield increment of biochar on wheat was 11.71% around China, and the yield increments were significant on loam soils (16.0%) and on the fields with pH of 6.5–7.5 (17.1%). The yield-increasing effects of biochar were varied among the derived raw materials, and in order of wood material (29.3%) > corn straw (10.7%) > wheat straw (8.1%) > rice straw (5.9%). Management measures affected the yield effects, that in rain-fed area (15.7%) was higher than in irrigation area (4.9%). The increase of nitrogen fertilizer application rate decreased the yield-increasing effect of biochar, and within the N application rate of 0–50 kg/hm², the yield increase was as high as 17.9%. The largest yield increase was at the biochar application rate of 10–25 t/hm² (14.9%). The significant yield-effect by biochar lasted for four seasons, then became not obvious, and the yield increasing was in order of the first season (17.2%) > the third season (13.4%) > the fourth season (9.4%) > the second season (7.3%). The application of biochar significantly increased soil total N, total P, total K, ammonium, nitrate, available P, available K, organic carbon, bulk density, pH, soil water content, C/N, and microbial biomass carbon, while the organic carbon content was increased the most (38.4%) .

Conclusions Biochar application could increase yield of wheat, with the largest increase at application rate of 10–25 t/hm², although the effects are varied under different management measures and soil properties. The yield-increasing effect of biochar normally last four seasons. Biochar application can significantly increase wheat yield and improve soil quality, but has no significant effect on soil microbial biomass nitrogen (SMBN). It is recommended that the application rate of biochar should be in range of 10 to 25 t/hm² during wheat production.