Effects of long-term shade on maize (Zea mays L.) growth and yield in west of Liaoning province, northeastern China

Light is one of the most important factors influencing crop growth and yield. With the aim of specially stressing the long-term shading effects in lowlight growing conditions on maize (Zea mays L.) growth and yield, a screen-shading experiment during the whole growing season was conducted in the northeastern China. In the experiment, four treatments of shading intensity (using screens with a light transmittance of 0.23, 0.38, 0.54 and 0.75) and control were employed to measure maize growth from germination to harvest. Leaf area index (LAI) and height (H) of the maize were measured at seedling, jointing, and booting stages; whereas yields of grain, cob, and stalk were measured during harvest. The results showed that maize growth and yield were seriously hindered by long-term shading. (1) The LAI of maize decreased mostly at the jointing stage, middle at booting stage and least at seedling stage.(2) The impact of the shading on the height of maize was similar among the three measuring stages, with relative heights of 0.65, 0.76, 0.85 and 0.94, respectively, for the four shading treatments. (3) Grain and cob yield dropped in a similar manner, with relative values of 0.21, 0.42, 0.66 and 0.87, respectively, for the four shading treatments. However, the maize stalk yield was comparatively higher, with relative values of 0.42, 0.56, 0.85 and 0.95, respectively, for the four shading treatments. In order to predict the growth and yield of maize under different light conditions, the regression equations between LAI, height, grain yield, cob yield, stalk yield and light transmittance were also established, respectively.