Effects of climate change and agricultural technology improvement on evapotranspiration and crop yield

Along with the development of farm mechanization, improved production conditions, varietal breeding and favorable climatic changes, crop yields have drastically increased across the globe. Despite this achievement, however, evapotranspiration has not continued to increase with increasing crop yields. To that end, meteorological data for 1955~2007 at Shijiazhuang Meteorological Station were analyzed for changes in seasonal climatic factors that affected winter wheat and summer maize. Long-term (1992~2009) irrigation experiments at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences (or Luancheng Station in short) were also used to study the effects of climate change on evapotranspiration and yield of winter wheat and summer maize. The studies showed that the use of farm machinery in Hebei Province increased by 7.3 times in 2007 over that in 1983. Mechanization rate of cultivation, planting and harvesting was 59.65%, indicating that farm mechanization in Hebei Province had entered the intermediate stage by 2007. Summer maize yield increased by 2.08% per year, and with winter wheat straw mulching, saved about 14 mm of water. For the period 1955~2007, climatic factors during winter wheat and summer maize seasons had also changed. The average sunshine duration, relative humidity, wind speed, daily temperature range had significantly dropped during the growing seasons of two crops. Minimum temperature, average temperature and accumulated temperature had increased significantly. Although the trends of change in climatic factors had not significantly affected evapotranspiration (ET₀), water demand for the two crops increased due to decreasing rainfall. Long-term irrigation experiments showed that winter wheat and summer maize yields greatly increased due to improvements in production conditions, varietal breeding and climate change. In recent years, however, evapotranspiration had been relatively stabilized due to the extensive application of improved water-saving technologies.