Yield stability of maize and characteristics of nitrogen distribution and accumulation in brown soil under different long-term fertilizations

Objectives The effects of long-term fertilization on maize yield stability, soil mineral nitrogen (N) distribution and accumulation were studied to provide theoretical basis for making reasonable fertilization management and ensuring sustainable development of agriculture in brown soil region in northeast China.

Methods This study was based on data collected from a 40-year (1979 to 2018) field experiment. Treatments included non-fertilization (CK), application of N fertilizer alone (N), application of N and phosphorus (P) fertilizers (NP), application of N, P, and potassium (K) fertilizers (NPK), application of manure alone at a low rate (M1) and with chemical fertilizers (M1N, M1NP, and M1NPK), application of manure alone at a high rate (M2) and with chemical fertilizers (M2N, M2NP, and M2NPK). Plant and soil samples were taken during maize harvesting in 2018 to illustrate crop N uptake, mineral N distribution and accumulation within 0–100 cm soil depth, and microbial biomass N (MBN) concentration within 0–40 cm soil layers.

Results Maize yield fluctuated across the treatments over the period, but was more stable during the period of 1979–1998 compared with 1999–2018. The highest average maize yields were found under M1NPK and M2NPK treatments and were 10.3% and 11.7% higher than that found under NPK treatment in the early 20 years and 17.1% and 19.4% higher in the late 20 years. The stability of maize yield increased with the increase in experimental years. Sustainable yield index (SYI) of maize with manure application was higher than that with chemical fertilizer alone. The contribution rate of fertilizer was greater in treatments with manure than those with chemical fertilizer alone, and was highest in M2NPK treatment (54%). Combined application of chemical fertilizer and manure at a low rate decreased mineral N within 100 cm soil layer. Application of manure at a high rate increased mineral N residual in 0–100 cm soil layer by 324.5% and 172.9% compared with those in plots with chemical fertilizer alone and combined application of chemical fertilizer and manure at a low rate, respectively. Additionally, both low and high manure application rates similarly enhanced MBN concentration in 0–40 cm soil.

Conclusions Long-term fertilization influenced yield stability, changed N distribution and accumulation in soil, and thus impacted maize N uptake. Combined application of manure at 13.5 t/hm² with N, P, and K fertilizers enhanced maize N uptake, reduced mineral N accumulation in 0–100 cm soil, which decreased N losses to the environment. The increased MBN concentration become potential N storage in soil to ensure a high and stable maize yield and friendly environment.