Optimal nitrogen fertilizer, which determines straw properties, and pyrolysis temperatures produce desired-biochars that can be used as a soil amendment

This study investigated the straw harvested after nitrogen (N) fertilizer application levels (0, 75, 150 and 225 kg N hm-2). The N fertilizer increased straw yield by 115.4-190.6%. In addition to N fertility, the pyrolysis tem-peratures (300, 500 and 700 degrees C) induced significant changes of the straw-derived biochar samples. The yield reduced from 41.4 wt% to 23.2 wt%, the residence time increased from 272 yr to 2194 yr, and the residual coefficient of organic C (Fperm) increased from 0.65 to 0.93 for the biochar samples as the temperature rising. The parameters of C sequestration were mainly affected by pyrolysis temperature. The N + P2O5+K2O content (5.6-8.8%) of the biochar samples was more in the 500 degrees C treatment. The characteristics of nutrient supply were affected by both the N fertility and pyrolysis temperature. The N fertilizer rate of 150 kg N hm2 in the soil for wheat straw, together with the 500 degrees C treatment induces the best nutrient donor and C sequestration after biochar incorporation into the soil.

Automated summary

This study investigated the effects of different nitrogen fertilizer application levels on straw yield and the influence of pyrolysis temperature on straw-derived biochar samples. The results showed that nitrogen fertilizer significantly increased straw yield, and pyrolysis temperature had a significant impact on the characteristics of the biochar samples. The treatment with a pyrolysis temperature of 500 degrees Celsius resulted in the highest nutrient content in the biochar samples.