Modelling Maize Yield, Soil Nitrogen Balance and Organic Carbon Changes Under Long-Term Fertilization in Northeast China

Abstract

Optimized fertilization is an effective strategy for improving nitrogen (N) use efficiency and maintaining high crop yield, but its long-term impacts on soil organic carbon (C) and inorganic N dynamics remains unclear. The objectives of this study were to 1) explore the economic optimum N rate and evaluate the DSSAT CERES-Maize model using the measurements from three 3-year maize ( Zea mays L.) field experiments, in Gongzhuling and Yushu County, Northeast China, and 2) assess the long-term impacts of farmers’ N rate (N250), optimum N rate (N180) and organic-inorganic combined N rate (MN180) on maize yields, soil N and C changes from 1985 to 2020. Results showed that the similar maize yield of 8000-11000 kg ha -1 were achieved under the average economic optimum N rate of 170 kg N ha-1 relztive to the N 250 in both counties. Good agreements were observed between the measured and simulated maize yield, above-ground biomass, N uptake and soil nitrate (NO 3 - -N). Long-term simulation confirmed that the N180 and MN180 can achieve the same yield as N250 in both counties. The lowest annual soil inorganic N balance, NO 3 - leaching and nitrous oxide (N 2 O) emission was achieved under the MN180, followed by the N180 in both sites. The higher NO 3 - leaching was found under sandy clay loam soil than silt clay loam and clay loam soils. Average soil organic C (0-0.2 m) increased from 1.3 to 2.4% in Gongzhuling and from 2.1 to 2.4% in Yushu under the MN180 during the 35-year period, but it showed declining trends under the N180 and N250. We concluded that the economic optimum N rate could be an option to replace current farmers’ N rate for the continuous maize. Substitution with 20-30% manure under the optimum N fertilization showed advantage on maintaining high yield, reducing soil inorganic N losses as well as increasing SOC stock for sustainable agriculture.

Keywords: DSSAT CERES-Maize model, maize yield, Optimum N rate, Soil N balance, Soil organic carbon