Journals
  Publication Years
  Keywords
Search within results Open Search
Please wait a minute...
For Selected: Toggle Thumbnails
Statistical analysis of nitrogen use efficiency in Northeast China using multiple linear regression and random forest
LIU Ying-xia, Gerard B. M. HEUVELINK, Zhanguo BAI, HE Ping, JIANG Rong, HUANG Shao-hui, XU Xin-peng
2022, 21 (12): 3637-3657.   DOI: 10.1016/j.jia.2022.08.054
Abstract342)      PDF in ScienceDirect      

Understanding the spatial-temporal dynamics of crop nitrogen (N) use efficiency (NUE) and the relationship with explanatory environmental variables can support land-use management and policymaking.  Nevertheless, the application of statistical models for evaluating the explanatory variables of space-time variation in crop NUE is still under-researched.  In this study, stepwise multiple linear regression (SMLR) and Random Forest (RF) were used to evaluate the spatial and temporal variation of NUE indicators (i.e., partial factor productivity of N (PFPN); partial nutrient balance of N (PNBN)) at county scale in Northeast China (Heilongjiang, Liaoning and Jilin provinces) from 1990 to 2015.  Explanatory variables included agricultural management practices, topography, climate, economy, soil and crop types.  Results revealed that the PFPN was higher in the northern parts and lower in the center of the Northeast China and PNBN increased from southern to northern parts during the 1990–2015 period.  The NUE indicators decreased with time in most counties during the study period.  The model efficiency coefficients of the SMLR and RF models were 0.44 and 0.84 for PFPN, and 0.67 and 0.89 for PNBN, respectively.  The RF model had higher relative importance of soil and climatic covariates and lower relative importance of crop covariates compared to the SMLR model.  The planting area index of vegetables and beans, soil clay content, saturated water content, enhanced vegetation index in November & December, soil bulk density, and annual minimum temperature were the main explanatory variables for both NUE indicators.  This is the first study to show the quantitative relative importance of explanatory variables for NUE at a county level in Northeast China using RF and SMLR.  This novel study gives reference measurements to improve crop NUE which is one of the most effective means of managing N for sustainable development, ensuring food security, alleviating environmental degradation and increasing farmer’s profitability.



Reference | Related Articles | Metrics
Regional distribution of wheat yield and chemical fertilizer requirements in China
XU Xin-peng, HE Ping, CHUAN Li-min, LIU Xiao-yan, LIU Ying-xia, ZHANG Jia-jia, HUANG Xiao-meng, QIU Shao-jun, ZHAO Shi-cheng, ZHOU Wei
2021, 20 (10): 2772-2780.   DOI: 10.1016/S2095-3119(20)63338-X
Abstract159)      PDF in ScienceDirect      
Quantification of currently attainable yield and fertilizer requirements can provide detailed information for assessing the food supply capacity and offer data support for agricultural decision-making.  Datasets from a total of 5 408 field experiments were collected from 2000 to 2015 across the major wheat production regions in China to analyze the spatial distribution of wheat yield, the soil nutrient supply capacity (represented by relative yield, defined as the ratio of the yield under the omission of one of nitrogen (N), phosphorus (P) and potassium (K) to the yield under the full NPK fertilizer application), and N, P and K fertilizer requirements by combining the kriging interpolation method with the Nutrient Expert Decision Support System for Wheat.  The results indicated that the average attainable yield was 6.4 t ha−1, with a coefficient of variation (CV) of 24.9% across all sites.  The yields in North-central China (NCC) and the northern part of the Middle and Lower reaches of the Yangtze River (MLYR) were generally higher than 7 t ha−1, whereas the yields in Southwest China (SWC), Northeast China (NEC), and the eastern part of Northwest China (NWC) were usually less than 6 t ha−1.  The precentage of area having a relative yield above 0.70, 0.85, and 0.85 for N, P, and K fertilizers accounted for 52.3, 74.7, and 95.9%, respectively.  Variation existed in N, P, and K fertilizer requirements, with a CV of 24.8, 23.9, and 29.9%, respectively, across all sites.  More fertilizer was needed in NCC and the northern part of the MLYR than in other regions.  The average fertilizer requirement was 162, 72, and 57 kg ha−1 for N, P2O5, and K2O fertilizers, respectively, across all sites.  The incorporation of the spatial variation of attainable yield and fertilizer requirements into wheat production practices would benefit sustainable wheat production and environmental safety.
Reference | Related Articles | Metrics