Yield Gap Analysis Focused On Winter Wheat And Summer Maize Rotation In The North China Plain

Because a strong increase in population and biomass energy as well as dietary changing, China food security problems have become more and more serious. To meet the growing demand for food and maintain food security, under the background of limited arable land resources, it was the only way to improve the yield per unit area. North China Plain (NCP) is one of the largest wheat and maize production regions in China, which play an important role in food security. Quantifying the size and variation of yield gaps between the actual on-farm yields and potential yields will be helpful for the further enhance the on-farm actual production. In this paper, we focused on the winter wheat and summer maize rotation systems. First, we simulated the potential yields of winter wheat and summer maize by agricultural production system simulation model (APSIM), considering the changes in variety during1981-2010. Meanwhile, a detailed analysis of the effects of climate change and cultivar replacement on potential yields was conducted. Sencond, we calculated the yield gaps of winter wheat and summer maize between on-farm yields and potential yields and its linear trends during1981-2010, based on actual yields at county level. Third, we were trying to find some efficient annual sowing management to improve the potentail yields and provide some suggestions for annual production. The main conclusions are as follows:(1) Potential yields of winter wheat and summer maize in the NCP increased from southwest to northeast, with a significant trend towarding latitude and longitude, and showed an increasing trend in1981-2010because of the combine effects of climate change and cultivar improvement, on average was45kg hm2per year and85kg hm2per year, respectively. The total solar radiation during growth period of winter wheat was the decisive factor of its temporal trends of potential yields and the reduced radiation resulted in winter wheat production decrease. However, the temporal trends of summer maize potential yields were affected by the minimum and daily range temperature and solar radiation in the past30years, where the solar radiation was the most powerful factors. The spatial distribution of winter wheat potential yields was mainly determined by the maximum temperature and total radiation together, where growth period total radiation dominated it. The main factors affecting the spatial distribution of potential yields of summer maize were temperature, where the minimum temperature played the maximum effects.(2) Without considering the cultivar changing, climate change shortened the length of vegetatable growth period and total growth period of winter wheat, whereas prolonged the reproductive growth period; while there was no uniform trend on the growth period of summer maize. Under climate unchange scenario, cultivar replacement could prolong the growth period of winter wheat and summer maize, especially for the reproductive growth period. Meanwhile, comparing the effects of cultivar replacement on the length of growth period of winter wheat and summer maize, summer maize was more obvious. Comparing the effects of climate change and cultivar replacement on the length of growth period, climate change dominated the change of the growth period of winter wheat, but cultivar change was the main reason for summer maize. In addiation, when cultivar was controlled, climate change reduced the potential yields of winter wheat and summer maize, but cultivar replacement could compensate this reduction and enhance potential yields.(3) The actual yields of winter wheat and summer maize significiantly increased during1981-2010, with an average of115kg hm"2and100kg hm"2, respectively. However, yields stagnation happened in33.6%of winter wheat area in the NCP, mainly locating in Hebei and Shandong provinces; and meanwhile, in29.3%of summer maize area, yields occurred stagnation, which mainly located in the central and western Shandong, central Hebei and north-central Henan province.(4) The area weighted average yield gaps between actual yields and potential yields of winter wheat in the NCP were3627kg hm-2, accounting for45%of potential yields. With80%of potential yields as the production ceiling which could be achieved on farmer land, the average on-farm yields in the NCP could still increase by2000kg hm-2. Meanwhile, the yield gaps of summer maize were3747kg hm-2, accounting for43%of potential yields, and the potential scope of raising maize yields was2004kg hm’2. In the past three decades, yield gaps of winter wheat has significantly decreased with a rate of69kg hm-2per year, while only a weak declined was happened in summer maize. Central Henan was the regions of low yield gaps of winter wheat, while western Shandong was summer maize’s. In these regions, potential yields will be an important limiting factor for on-farm yields increase in the next decade.