Integrated agronomic measures increase maize production, environmental efficiency, and soil fertility in Northeast China

Objectives We proposed and tested an integrated measurement for efficient spring maize production considering planting density, fertilizer application rate and time in northeast China.

Methods A field experiment was conducted for three years, from 2017 to 2019, in Nong’an County, Jilin Province, using spring cultivar Fumin 108 as the experimental material. The treatments included no fertilizer (CK) and local farmers’mode as the control (FP), high-yield and high-efficiency model (HH), and super-high-yield model (SH). We set up an extra no-nitrogen fertilizer treatment in all FP, HH, and SH to calculate fertilizer utilization rate and soil nitrogen balance. Plant samples were collected at the main 6 growing stages of maize to determine N content and uptake; 0–40 cm soil samples were collected to determine NH₄⁺-N and NO₃^–-N. We investigated maize yield at harvest.

Results Maize grain yield was in the order SH>HH>FP>CK. SH’s maize yield was 8.76%, 20.16%, and 106.91% higher than HH, FP, and CK, respectively. HH produced the highest nitrogen partial productivity, which was 37.92% and 45.65% higher than FP and SH. Similarly, HH recorded the highest nitrogen agronomic efficiency (AE_N) and nitrogen recovery efficiency (RE_N), which were 21.21% and 35.72% (AE_N) and 9.69% and 63.56% (RE_N) higher than SH and FP, respectively. There was no significant difference (P>0.05) in plant N accumulation among FP, HH, and SH from V3–V6. However, the total rate of accumulated N in the reproductive growth stage (R1 to R6) was in the order SH (36.21%)>HH (34.60%)>FP (29.75%)>CK (26.33%). The proportion of grain N accumulation absorbed post-silking increased with yield increase, and the contribution rates of SH, HH, FP and CK were 48.43%, 44.78%, 40.40% and 35.39%, respectively. FP had the highest mineral N content in 0–20 cm and 20–40 cm soil layers before silking, and SH had the highest from silking to maturity. SH had 12.00% and 4.05% (0–20 cm), and 14.81% and 4.93% (20–40 cm) higher mineral N content than FP and HH. HH had (P<0.05) lower apparent N loss than FP and SH, while FP had the highest N surplus and was 23.36% and 5.25% higher than HH and SH. HH had the highest net income, while SH recorded the lowest; the income from HH was 14.38% and 18.30% higher than FP and SH.

Conclusions The proposed integrated measurement recorded the highest nitrogen use efficiency, lowest nitrogen loss, acceptable yield, and lowest environmental risk potential. The high-yield and high-efficient treatment (i.e., planting density of 7.5×10⁴ plants/hm², split nitrogen fertilizer application, combined with deep ploughing in autumn and deep subsoiling in summer) led to the synergistic improvement of spring maize yield and nitrogen use efficiency.