Low yield gap of winter wheat in the North China Plain

The yield gap (YG) between the potential yields (Yp) and the average on-farm yields (Ya) is an indicator of the potential improvement for crop production. Understanding how large the current gap is and how this gap has changed over the past few decades is essential for increasing wheat production to meet increased food demand in China. This paper describes a study conducted using an APSIM-Wheat model and farm-level crop yield to analyze the spatio-temporal distribution of the yield gap of winter wheat from 1981 to 2010 in the North China Plain. Nine varieties were calibrated and evaluated based on the data from 16 agro-meteorological experimental sites and then potential yields were estimated considering cultivar replacement. In addition, a trend pattern analysis of on-farm yields for the period 1981–2010 was conducted. Results revealed an estimated yield gap across the entire North China Plain region of 1140–6810 kg ha⁻¹, with a weight average of 3630 kg ha⁻¹ in 1981–2010. Expressed as a relative yield (yield gap % of potential yields), the range was 15–80%, and the weight average was 45%. Despite the negative effects of increasing temperature and decreasing radiation, the potential yields significantly increased by 45 kg ha⁻¹ per year due to cultivar improvement. On-farm yields increased even more notably because of new cultivar selection, increased fertilizer application and other management improvements, but were stagnating in 32.3% of wheat areas, located mainly in Hebei province, Shandong province, Beijing and Tianjin. The improvement of on-farm yields have substantially contributed to yield gap spatio-temporal variation. As a result, the yield gap decreased from 4200 kg ha⁻¹ (56%) in 1981–1990 to 3000 kg ha⁻¹ (35%) in 2001–2010 at a rate of −69 kg ha⁻¹ per year. However, yields stagnation will expand to the northern Henan province without cultivar potential productivity improving, where yield gap was close to or less than 20% of the potential yields and proved difficult to reduce. To further improve the total production of winter wheat in the coming decades, efforts should be paid to break the potential ceiling and reduce the yield gap by breeding higher yield variety and introduction of new agricultural technology.     

基于APSIM模型播期对未来气候变化情景下旱地春小麦产量和生育期影响的模拟分析

为明确未来气候变化与播期调控对旱地春小麦（Triticum aestivum L.）产量的互作效应,以陇中黄土丘陵沟壑区为研究区域,首先利用甘肃农业大学试验区2016-2018年不同播期下的春小麦产量和生育日期对APSIM-Wheat模型进行适用性验证,然后基于RegCM4.6模型和HadGEM2-ES预测两个典型气候情景RCP4.5和RCP8.5下西北地区未来2020-2060年的气候变化,最后通过验证后的APSIM-Wheat模型结合未来气象数据,模拟RCP4.5和RCP8.5情景下不同播期（早播、正常播、晚播）对试验区2007-2019（基准期）、2020-2060年（未来分析期）春小麦生育期、产量和生物量的影响。结果表明,APSIM-Wheat模型能够较精确地模拟试验区小麦产量和生育日期。在RCP4.5和RCP8.5情景下,2020-2060年年均日最高温度较基准期分别升高0.8和0.9 ℃,年均日最低温度分别升高0.9 和1.1 ℃,降水量分别增加31.5 和44.2 mm,升高趋势均表现为RCP8.5> RCP4.5;不同气候情景下随着播期的推迟,小麦生育阶段天数较基准期不同程度缩短;两种气候情景下,2020-2060 年早播、正常播和晚播处理的春小麦产量和生物量较基准期均增加,产量增长率表现为早播>正常播>晚播,生物量增长率表现为正常播>早播>晚播;2种气候情景下播期调控对春小麦播种到出苗、出苗到开花阶段的影响均达到极显著水平。