*2.2. Field Measurements*

In Changchun, the five typical maize plots (named H1 to H5, Figure 1f) were equipped with five sets of canopy temperature and meteorology monitoring systems (CTMS) (Figure 1e), which are composed of a stainless-steel stand column, solar panels, and various sensors. This system can synchronously monitor field data at 30 min intervals, including wind speed (014MINI-MetOne, Washington, USA), solar radiation (SP110-Apogee/SQ110-Apogee, Logan, USA), the crop canopy temperature (TPiS 1 T 1252B, Excelitas, Waltham, Germany), air temperature/humidity (HMP60-Vaisala, Vantaa, Finland), soil temperature/moisture (20 cm and 40 cm in the root zone) (SM10D, Beijing, China), and more by the corresponding sensors. It should be emphasized that the canopy temperature at 30 min intervals was computed as the average of multi-point values around the equipment by the rotation measurement of a thermal infrared sensor (TPiS 1 T 1252B, Excelitas, Waltham, Germany) installed at the end of a cantilever perpendicular to the stand column. Sensors were set up at a height of 3 m during the whole growth stage, which could be adjusted as need. Regular weekly maintenance ensured the normal functioning of the equipment. A more detailed description of the system was provided by Cai et al. [37] and Huang et al. [40].

**Figure 1.** Overview of the two study areas: (**a**) locations in China; (**b**) land-use and -cover map in Changchun from the GlobeLand30 platform (in 2020); (**c**) distributions of experimental station and eight yield monitoring points in Jiefangzha sub-irrigation district; (**d**,**e**) a typical CTMS equipment in Jiefangzha/Changchun; (**f**) locations of the five sets of CTMS equipment (H1 to H5) in Changchun.

**Figure 2.** Precipitations and soil water contents changing during maize growing season in Changchun during three years: (**a**) 2017; (**b**) 2018; (**c**) 2019.

Above-ground biomass was sampled every 10–15 days by removing three representative plants from each of monitoring plots. The collected samples were immediately weighted as the amount of FBA. Then, these samples were put in an oven at 105 ◦C for 30 min to stop the plant life activities and subsequently were dried at 80 ◦C to a constant

weight. (The final weight would be the DBA.) During the harvest, the last sampling of above-ground biomass was recorded, and the grain yield (1 m2) and planting density were measured in each experimental point at the same time. In conclusion, six samples were collected from each plot per year.

Similarly, a CTMS system was installed in the Shahaoqu experimental station to collect the same data as Changchun, and eight yield monitoring points were erected to measure final grain yield for evaluation in the Jiefangzha sub-irrigation district (Figure 1c). Furthermore, above-ground biomass in the experimental site was sampled and recorded four times as a driving force for yield forecasting. More details can be seen in the report from Bai et al. [39].
