Simulating the Impact of Long-Term Fertilization on Basic Soil Productivity in a Rainfed Winter Wheat System

Basic soil productivity (BSP) is the ability of a soil, in its normal environment to support plant growth. However, the assessment of BSP remains controversial. The aim of this study is to quantify and analyze the trends of BSP in winter wheat seasons using the decision support system for agrotechnologie transfer (DSSAT) model under a long-term fertilization experiment in the dark loessal soil region of the Loess Plateau of China. In addition, we evaluated the contribution percentage of BSP to yield and its influencing factors. A long-term fertilization experiment with a winter wheat/spring maize rotation was established in 1979 in a field of the Gaoping Agronomy Farm, Pingliang, Gansu, China, including six treatments: (1) no fertilizer as a control (CK), (2) chemical nitrogen fertilizer input annually (N), (3) chemical nitrogen and phosphorus fertilizer input annually (NP), (4) straw return and chemical nitrogen fertilizer input annually plus phosphorus fertilizer added every second year (SNP), (5) manure input annually (M), and (6) M plus N and P fertilizers added annually (MNP). The application of the DSSAT-CERES-Wheat model showed a satisfactory performance with good Wilmott d-index (0.78~0.95) and normalized root mean square error (NRMSE) (7.03%~18.72%) values for the tested genetic parameters of winter wheat. After the 26-years experiment, the yield by BSP of winter wheat under the M and MNP treatment significantly increased, at the rate of 2.7% and 3.82% a year, respectively, whereas that of CK and N treatments significantly decreased, at the rate of 0.23% and 3.03%. Moreover, the average contribution percentage of BSP to yield was 47.0%, 39.4%, 56.3%, 50.0%, and 61.9% in N, NP, SNP, M, and MNP treatments, respectively. In addition, soil organic carbon contents were the main controls of BSP under the different fertilization conditions in the dark loessial soil area. As a result, the combined application of organic fertilizer or straw and chemical fertilizer can be an effective form of fertilization management to greatly enrich basic soil productivity, continually promote the contribution percentage of BSP, and ultimately increase crop yield.