Zhang Weijian

System design of Free Air Temperature Increased (FATI) for field nighttime warming experiment and its effects on rice-wheat cropping system.

There is evident asymmetry in climate warming between daytime and nighttime with the highest warming rate occur-ring at nighttime. Since there are high uncertainties in the projecting of climate warming effects on crop production using crop models,it is essential to design a reliable field warming system to study the responses of crop production system to nighttime warming in field. Therefore,based on existing field warming facilities in the world,we designed a rice-wheat warming system in Nanjing,Jiangsu province,the first facility of Free Air Temperature Increased (FATI) for crop production in China,to study the effects of nighttime warming on crop growing duration and yields during 2006–2009. The results showed that the warming effect of this facility was significant and well-distributed within 2 m × 2 m area. In sunny,rainy and cloudy days,the night temperatures on the field surface within the 4 m2 warming area were increased by 2.4℃ ,2.3℃ ,and 2.1℃ on average on the tested turfgrass land. At the vertical dimension,the night temperatures of 5 cm underground,ground surface,40 cm aboveground,and 90 cm aboveground were enhanced by 1.2 ℃,2.2 ℃,0.7 ℃,and 2.3 ℃ on average. In the rice growing period,the night temperatures of 5 cm underground,field surface,the middle part of crop community and the canopy were 0.7℃,0.6℃,1.0℃,and 1.6℃ higher compared to the un-warming plots,respectively. In the winter-wheat growing period,the increments were 1.2℃,1.5℃ ,1.8℃ ,and 1.9 ℃,respectively. During the whole crop growing period,the trends of diurnal change of the above temperatures in warming plots were all similar with those in the un-warming plots. The distributed characteristics of soil moisture in wheat field were not significantly changed under this warming facility but with a slightly decreasing trend. The decrements of soil moisture in the 0–25 cm soil layers were all within the scale of 0.99–1.62 percentage points with no significant difference compared to the un-warming control. Under this warming facility,rice and wheat growing stages were significantly changed,and the durations of rice and wheat from the sowing date to the initial heading date were shortened by 2.5 d and 11.5 d respectively. Nighttime warming reduced rice yield by 4.51%,but increased wheat yield by 18.30% on average. Although,there existed significant differences in the warming rates among different stages of crop growing by using the warming facility,evident seasonal discrepancy of warming rates also often occurred in the real fields under climate warming situation. Therefore,the above results suggest that this night warming facility meets with the temperature characteristics of climate warming and can be used for studies on the responses of crop production system to nighttime warming.