基于DSSAT模型的氮肥管理下华北地区冬小麦产量差的模拟

为了评价氮肥管理对华北地区冬小麦产量差的影响,利用大田试验数据和田间调查的方法,应用DSSAT模型分析了吴桥不同氮肥水平下冬小麦多年平均可获得产量及产量差,并研究了不同地块产量差和氮肥农学效率差的分布。结果表明,不同地块冬小麦产量差异显著,但产量变异较小,地块间施肥水平存在明显差异,且变异较大。模型分析确定222 kg/hm2为最佳施氮肥量,对应的最大可获得产量为7618 kg/hm2,地块产量与最大可获得产量有较大差距,当地冬小麦产量具有一定的提升空间。75%的农户地块的施氮量高于最佳施氮量,且氮肥农学效率普遍偏低。因此,生产中应优化氮肥管理方案,适当减氮并调整施肥时期和改进技术,提高氮肥农学效率,以实现冬小麦生产高产高效。在保障国家粮食安全和保护自然环境双重压力的背景下,通过合理的氮肥管理来缩减冬小麦产量差对提高中国粮食总产及保持农业可持续发展具有重要的意义。

Simulating yield gap of winter wheat in response to nitrogen management in North China Plain based on DSSAT model

Abstract: Yield gap analysis is important to reveal factors that limit crop production and identify management practices that can potentially increase crop yield. Although nitrogen (N) fertilizer played an important role in wheat yield increase in the past 30 years in China, excessive nitrogen application became a common practice in some farms, which increased input by farmers, reduced farm profitability, and caused significant environmental issues in recent years. Due to the complexity of the system, crop growth models such as the DSSAT model (Decision Support System for Agro-technology Transfer) have been widely used by many researchers across the world to analyze crop yield gap and determine the impact of N fertilizer on yield gap. In this study, the DSSAT model was coupled with data from experiments and a farm survey was employed to assess the impact of N fertilizer management on the yield gap of winter wheat in the North China Plain, to determine the average yields and yield gaps under distinct N fertilizer management scenarios over the years, and to identify the distribution of yield gaps and the agronomic efficiency of applied N fertilizer (AEN) among different fields. The field experiments were conducted in Wuqiao, China from 2008 to 2011. Yield and management data were collected from the experiments to calibrate and validate the DSSAT model and the analysis of AEN in the experiment. The simulated yields of the DSSAT model were closely correlated to the actual yield in the field experiments with different application levels of N fertilizer, indicating that the model was adequate for analyzing the yield gap of winter wheat in the region. Results from a farm survey, conducted in Wuqiao in 2010, indicated that there were remarkable differences among winter wheat yields in different fields, ranging from 5250 to 8630 kg/hm2 with a relatively lower coefficient of variation. The N fertilizer rates ranged from 30 to 495 kg/hm2 with significant variations among different fields, indicating a wide range of N fertilizer application rates among farmers in the region and room for improvement in management practices. Based upon the simulation results, the optimum N application rate was 222 kg/hm2 with the corresponding maximum attainable yield (AYmax) of 7618 kg/hm2. There were considerable differences between AYmax and crop yields from the survey, ranging from -1007 to 2 368 kg/hm2. The gap narrowed gradually as the N fertilizer rate increased and plateaued at a 222 kg/hm2 N fertilizer rate. The N application rates in farmers' fields were commonly higher than the optimum rate with low AEN. Almost 75% of the fields in the survey were in the range of relatively high N rates, indicating excessive N fertilizer applications in the wheat crop in the region. The results indicated that winter wheat yield could be significantly improved with better management practices. Possible optimization strategies to achieve both high yields and high N use efficiency in winter wheat in North China Plain should focus on adjusting N fertilizer application rates to an optimal range, improving N fertilizer application timing, and adjusting the practices according to local soil conditions and climates. Greater efforts in education and on-farm demonstration are needed to help farmers in improving N fertilizer management practices.