Using DNDC model to study the potential of nitrogen fertilizer reduction in spring maize production under long-term straw return

Objectives This study focused on the potential of nitrogen fertilizer reduction as affected by straw return, aiming to provide a theoretical basis for efficient nutrient management in spring maize production of Northeast China.

Methods A split plot experiment was carried out in Gongzhuling City, Jilin Province from 2017 to 2020. The treatments were under conditions of straw return and removal, nitrogen (N) fertilizer was applied at 6 rates, as: 0, 70, 140, 210, 280 and 350 kg/hm², respectively. The denitrification-decomposition model (DNDC) was calibrated and validated based on the field experimental measurements, then used to simulate the impact of straw return and removal on maize yield and N use efficiency, and predict the potential of N fertilizer reduction over a 30-year period (1991−2020).

Results The calibrated DNDC model well simulated the spring maize yield, biomass, N uptake, and soil inorganic N content of the treatments, the normalized average relative errors (nARE) averaged −5.7%−7.6% and the normalized root mean square errors (nRMSE) averaged 10.0%−28.5%. According to the simulations, long-term straw return increased the maize yield, N recovery efficiency, agronomic efficiency, and partial productivity of N under the maximum yield N rate by 6.0%, 5.5%, 2.7 kg/kg, and 6.7 kg/kg, respectively, and decreased N surplus rate by 36.3%, relative to those of straw removal. Straw returns reduced N fertilizer requirement by 35.5 kg/hm² (18.4%) to reach the maximum yield under straw removal. Compared to the N input under straw removal from 1991 to 2020, the N fertilizer reduction potential by straw return first increased and then decreased to a plateau level. The average reduction potential was as high as 23.6% during 7th−15th years, and then declined to 15.8% during 19th−30th years of straw return. The annual precipitation influenced the reduction potential of straw return, the average reduction potential was 20.5% in wet years, 18.7% in normal years, and 15.4% in dry years.

Conclusions Long-term straw return increases the maize yield and N use efficiency, decreases the N fertilizer input and N surplus significantly. According to the DNDC model simulations, the relatively steady N fertilizer reduction rate by straw return is 10%−20%, depending on the annual precipitation in the spring maize area of Northeast China.