JIA-2019-11

2621 WANG Shi-chao et al. Journal of Integrative Agriculture 2019, 18(11): 2619–2627 rice-rice rotation in southern China. The CPISP results presenting for the different cropping systems were based on an analysis of 27 typical long-term experiments (LTEs). The typical LTEs were established in the 1980s or 1990s and included five experiments on single maize (or wheat) in Northeast China, five on single wheat (or maize) in Northwest China, six on wheat-maize in northern China, and five on wheat-rice and six on double rice in southern China. An overview of the cropping systems, the regional distribution of the soils, and the land use types involved in this study is presented in Table 1. 2.2. Experimental design Two treatments were selected in the same field: (1) no fertilizer treatment (NFT); (2) conventional fertilizer treatment (CFT). For CFT, the fertilization rates represented the average levels of the study area. NFT plots in upland areas were 60 m 2 or larger and isolated by strips between plots. NFT plots in paddy fields were 30–70 m 2 and isolated by cement boards or other separators to prevent the horizontal movement of water and nutrients. CFT plots were at least 333 m 2 for both upland and paddy field sites. With the exception of fertilizer inputs, CFT and NFT plots were treated identically at each site with regard to tillage, cultivation, irrigation, drainage, and other management practices. The fertilizer types and application rates of CFT treatments were consistent with the fertilizer rates used by local farmers at each monitoring site. Crop yields at each site for the NFT or CFT treatments were estimated from five subplots of rice and wheat (1–2 m 2 ) or maize (5–10 m 2 ). 2.3. Data treatment and statistics The CPISP value for each soil and crop at each monitoring site was calculated according to eq. (1). To reduce the error of the single annual value for CPISP, the average ratio of the first three years after each monitoring point was built as the CPISP3 value. In this study, inherent soil productivity was assessed by NFT. These plots received neither organic fertilizers (i.e., crop straw and manure) nor chemical fertilizers. For the CFT treatment, mineral N, P, and K fertilizers were applied at the farmer application rate. CPISP (%)= ×100 Yield in CFT Yield in NFT (1) All data were collected using Excel 2010. Figures were drawn in Sigmaplot 12.5 professional version (Systat Company, USA). The CPISP and CPISP3 values were analysed using one-way ANOVA with an LSD test in SAS (SAS Institute 2004), and these mean values were compared by the least significant difference at the 5% level using Tuckey’s test. Linear and/or no-linear regression was used to determine relationships between CPISP3/CPISP and year under different crop species and cropping system. 3. Results 3.1. Trends in CPISP CPISP3 values were influenced by many factors, such as Table 1 Regional distributions of soils, cropping systems and land use types in China Region Site 1) Climate Major soil 2) Cropping system Land use Number of long- term trials Northeast Heilongjiang, Jilin, Liaoning, east of Inner Mongolia Temperate, semi-humid Black soil, brown soil Single wheat/maize Upland 5 Northwest Xinjiang, Qinhai, Gansu, Ningxia, Shanxi, west of Inner Mongolia, north of Shaanxi Temperate, arid-semiarid Grey desert soil, irrigated desert soil Single wheat/maize Upland 5 Northern Beijing, Tianjin, Hebei, Shandong, Henan, south of Shanxi Warm- temperate, semi-humid Cinnamon fluvo-aquic soil, heavy loam fluvo-aquic soil, fluvo-aquic soil, cinnamon soil, light loam fluvo-aquic soil, non-calcareous fluvo-aquic soil Wheat-maize rotation Upland 6 Southern Sichuan, Chongqing, Hubei, Hunan, Anhui, Jiangsu, Jiangxi, Shanghai, Fujian, Zhejiang, Guangxi, Guangdong, Guizhou, Yunnan, Hainan Tropical- subtropical, humid Alkaline purplish soil, neutral purplish soil, yellow soil Wheat-rice and rice-rice rotation Upland-paddy, paddy 11 (5 wheat-rice rotation and 6 rice- rice rotation) 1) Soil type in the study area is classified according to the Chinese Soil Taxonomy.