Annual burying of straw after pelletizing: A novel and feasible way to improve soil fertility and productivity in Northeast China

Increasing the amount of straw returning has the potential to improve soil fertility, but is not widely accepted due to yield reductions in regions with low temperatures and precipitation. Thus, annual straw burying with large amounts after pelletizing was established considering soil fertility, crop yield and economic income. A three-year field trial with a large amount (75 Mg ha−1 year−1) of pelletized straw (PS75) and chopped straw (CS75), normal amount (15 Mg ha−1 year−1) of chopped straw (CS15), and no straw returning (CK) was conducted for spring maize. PS75 increased the soil total carbon content by 8–17 % and 29–51 % as compared to the other treatments between 0–20 and 20–40 cm respectively. PS75 also had a higher total nitrogen content, moderate soil C/N ratio, lower bulk density, and comparable soil pH in the third year. Specifically, PS75 increased grain yield by 5–7 % relative to CK, and 6–21 % relative to CS15 in the second and third years. PS75 also increased grain yield by 5–28 % than CS75 in the three years with higher kernel number and 100-kernel weight. This was partly attributed to a longer grain filling period due to higher soil carbon and nitrogen contents for PS75 than others. Notably, PS75 exhibited increased trends in grain yield and economic income with experimental year compared to CK. Overall, annual pelletized straw burying with a large amount is a feasible pathway for improving the soil fertility and crop yield in Northeast China.