中国科学院水利部水土保持研究所机构知识库

黄土高原是中国主要的冬小麦产地之一，探究该地区实际产量、水分限制产量、氮素限制产量与潜在产量之间产量差的时空分布特征，有助于定量估计区域内冬小麦产量的可提升空间，揭示限制产量提高的主要因素，明确未来提升作物产量的重点区域和优化增产的关键措施。本研究在全球产量差评估系统中的GYGA-ED（Global Yield Gap Atlas Extrapolation Domain）法划分的气候区基础上，根据冬小麦生育期内需要的有效生长积温(GDD)、干旱指数（年平均降水量/年平均蒸腾量）、DEM和地形因素，在保持了县界完整性的前提下，将黄土高原冬小麦种植区划分为4个农业气候区（Ⅰ，Ⅱ，Ⅲ和Ⅳ）。基于冬小麦种植区内32个气象站1961-2016年逐日气象资料、土壤数据、作物管理资料和各省市的统计年鉴，结合APSIM–Wheat模型模拟和ArcGIS空间分析功能，分析研究区冬小麦各级产量差的时空分布特征，解析引起产量差的主要限制因素并量化其限制程度。根据1961-2016年冬小麦生长季内逐年的降水量，将其划分为三种降水年型，明确了不同降水年型下的灌溉水利用效率（Irrigation water use efficiency，IWUE）和氮肥农学效率（Agronomic efficiency of applied Nitrogen，AE_N），并探讨了不同降水年型下黄土高原各区域冬小麦产量的提升空间。主要结果如下：

（1）1961-2016年黄土高原冬小麦潜在产量最高，氮素限制产量最低，产量面积加权平均值分别为8868.62kgha^-1和5415.61 kgha^-1。55年来潜在产量、水分限制产量每年分别减少9.6 kg ha^-1、21.17 kg ha^-1yr^-1，氮素限制产量则每年增加0.92kg ha^-1。水分限制产量变异系数最大，为14.3%，该产量稳定性最差。各气候区中，Ⅰ区冬小麦潜在产量最高，氮素限制产量最低。Ⅲ区潜在产量最低而氮素限制产量最高。Ⅱ区水分限制产量最高，而Ⅳ区水分限制产量最低。

（2）气候变化背景下，冬小麦生长季内的太阳辐射、降水量、最高温度分别是影响黄土高原冬小麦潜在产量、水分限制产量和氮素限制产量的主要因素，均为正效应（P<0.01），相关系数分别为0.64、0.83和0.63。

（3）黄土高原冬小麦实际产量的空间差异明显，整体呈西北高东南低的空间分布特征，全区平均产量为3382kg ha^-1，以每年增加64.99 kg ha^-1的幅度上升。提高Ⅰ区的化肥施入，Ⅱ和Ⅲ区的农业机械投入，Ⅳ区的灌溉量可以最大程度地增产。

（4）黄土高原冬小麦产量仍旧具有很大的提升空间，影响各气候区产量提高的主要限制因素不同。黄土高原冬小麦实际产量仅达到潜在产量的43%，提升空间较大。两者之间产量差的平均值为5046.58 kg ha^-1，2005-2016年，以每年174.62 kg ha^-1的幅度下降。水分限制产量占潜在产量的比例为73％，仍旧有一定的提升空间。两者之间产量差的平均值为2353 kg ha^-1。55年来该产量差平均每年增加11.57 kg ha^-1。由氮素限制引起的产量差平均为3430 kg ha^-1。氮素限制产量占潜在产量的比例为61％，提升空间稍大。55年来该产量差呈缩小趋势，每年下降11.57 kg ha^-1。氮肥对黄土高原冬小麦产量影响最大，水分其次，但是对各地区的影响程度不同，其中氮肥水平对Ⅰ区的影响最大，水分投入对Ⅳ区的影响最大。

（5）干旱年型黄土高原冬小麦IWUE最高，为52.31%。在该年型下通过补充灌溉，产量的可提升空间最高，为39.9%。各气候区中，增加Ⅰ区的灌溉投入，得到的收益回报更大。湿润年型黄土高原冬小麦AE_N最高，为50.11%。该年型下施加氮肥产量提升空间最高，为40.3%。提高Ⅲ区的氮肥利用效率是缩减该区氮肥限制造成的产量差的关键。

The Loess Plateau is one of the major winter wheat producing areas in China. We focused on the spatial distribution characteristics and temporal variation trends of yield gaps in four agricultural climatic zones of the Loess Plateau, including yield gap between actual yield and potential yield, yield gap between water limited yield and potential yield, and yield gap between nitrogen limited yield and potential yield. This will help to estimate quantitatively the improvement space of winter wheat yield in the study area, reveal the factors that limit the yield increase, and identify the significant regions to increase winter wheat yield in the future, as well as practical measures to increase yield. In this study, we based on the climate region of the GYGA-ED (Global Yield Gap Atlas Extrapolation Domain) method in the global yield difference assessment system, according to the growing degree days (GDD), the annual aridity index (the mean annual precipitation/the mean annual potential evapotranspiration), DEM and topographical factors, under the premise that maintained the integrity of the county line, the loess plateau winter wheat planting area can be divided into four agricultural climate zones (Ⅰ, Ⅱ, Ⅲ and Ⅳ). Based on the climate conditions, soil data, crop management data and statistical data, we used the APSIM–Wheat model and ArcGIS to analyze the temporal and spatial distribution characteristics of the winter wheat yield gaps in the study area, analyze the main limiting factors that cause the yield gaps, and quantify the degree of restriction. We have clarified the irrigation water use efficiency (IWUE) and agronomic efficiency of applied nitrogen (AE_N) under different category years, and explored the improvement space of winter wheat yield in each agricultural climatic zones of the Loess Plateau. Main results were as follows:

(1) From 1961 to 2016, the weighted average planting area of the potential yield and nitrogen limited yield of winter wheat on the Loess Plateau are 8868.62kgha^-1 and 5415.61kgha^-1, respectively. In the past 55 years, the potential yield and water limited yield decreased by 9.6 kgha^-1, 21.17kgha^-1 and nitrogen limited yield increased by 0.92 kgha^-1. The coefficient of variation of water limited yield is 14.3%, respectively. It can be seen that the water limited yield in the Loess Plateau is low and the stability is poor. Among the climatic zones, the potential yield of zoneⅠis the highest, and that of nitrogen limited yield is the lowest. Zone Ⅲ has the lowest potential yield, while its nitrogen limited yield the highest. Zone Ⅱhas the highest water limited yield and Zone Ⅳ has the lowest water limited yield.

(2) Under the background of climate change, the solar radiation, precipitation and the maximum temperature in the growing season of winter wheat are the main factors affecting the potential yield, water restricted yield and nitrogen limited yield of winter wheat in the whole Loess Plateau, all of which are positive effects (P<0.01), and the correlation coefficients are 0.64, 0.83 and 0.63, respectively.

(3) The spatial difference of actual yield of winter wheat in the Loess Plateau is obvious, and overall spatial distribution is high in the northwest and low in the southeast. The average yield of the whole region is 3382kg ha^-1. In the past decade, the average actual yield has significantly increased with a rate of 64.99 kg ha^-1 per year. Increase fertilizer application in Zone Ⅰ, agricultural machinery inputs in Zones Ⅱand Ⅲ, and irrigation in Zone Ⅳ can increase yield of winter wheat to the greatest extent.

(4) The winter wheat yield on the Loess Plateau still has a lot of room for improvement, and the main limiting factors affecting the yield increase in each climate zone are different. The average yield gap between the potential yield and the actual yield of winter wheat on the Loess Plateau is 5,416.58 kg ha^-1, according for 57% of potential yield, which has a large scope for improvement. The yield gap has decreased with a rate of 174.62 kg ha^-1 yr^-1in the past 11 years. The average yield gap between winter wheat potential yield and water limited yield is 2353 kg ha^-1, according for 27% of potential yield. In the past 55 years, the yield gap has increased with a rate of 11.57 kg ha^-1 yr^-1. The yield gap caused by nitrogen limitation of winter wheat on the Loess Plateau is 3430 kgha^-1. The ratio of nitrogen limited yield to potential yield is 61%, and the scope for improvement is large. The yield gap has decreased with a rate of 11.57 kg ha^-1 per year during the past 55 years. It can be seen from the above analysis that nitrogen has the greatest impact on winter wheat yield in Loess Plateau, followed by water, but the degree of impact on each agricultural climatic zone is different. Nitrogen has the greatest impact on Zone I, and water input has the greatest impact on Zone Ⅳ.

(5) The IWUE of winter wheat in Loess Plateau was the highest in the dry years, which was 52.31%. In this precipitation year type, the yield can be improved by supplementary irrigation with the highest space of 39.9%. Under different climatic zones, the irrigation input of ZoneⅠis increased, and the return on income is greater. The AE_N of the wet years loess plateau was the highest, which was 50.11%. In this precipitation year type, application of nitrogen fertilizer production has the highest room for improvement, at 40.3%. Increasing the efficiency of nitrogen use in Zone Ⅲ is the key to reducing the yield difference caused by nitrogen fertilizer restrictions in this area.