Effect Mechanism of Solar Radiation on Maize Yield Formation

Solar dimming due to global climate change is becoming increasingly more common in some agricultural areas. Such low-light stress inhibits maize ear number, kernel number per unit area (KN), and kernel weight (KW) as vital yield components. However, which yield component factors are most important for yield formation under low-light stress remains unknown. In this study at Qitai Farm in Xinjiang, China, in 2019 and 2020, we planted three maize ( Zea mays L.) cultivars (Denghai 618 (DH618), Xianyu 335 (XY335), and Zhengdan 958 (ZD958)) at two densities (7.5 × 10 4 (D1) and 12 × 10 4 (D2) plants ha −1 ). We used four shading treatments (85% (S1), 70% (S2), and 50% (S3) natural light and no shading (CK)) from the three-leaf stage until maturity to create different light conditions. KN was the key factor that directly affected yield under low-light stress. For every 100 MJ m −2 decrease in photosynthetically active radiation (PAR), the KN decreased by 803.2 kernels per m 2 . When the PAR was >674.3 MJ m −2 , KW tended to stabilize at 36.2 g/hundred kernels and the growth rate was 5.82 g/100 MJ m −2 per hundred kernels. DH618 and XY335 KNs were more sensitive to lowered solar radiation than ZD958. When density increased, DH618 required fewer light resources than the other cultivars to produce an equivalent amount of photosynthates for kernels. Therefore, in the face of climate change, particularly solar dimming, there is an urgent need to breed maize cultivars, such as DH618, with low-light stress tolerance and high grain yield.