Responses of yield traits to planting density and cultivar of spring maize in drylands under different rainfall types

Abstract: A maize yield can depend greatly on the rainfall types in dryland agriculture. This study aims to investigate the effects of planting density on the yield traits of spring maize under different rainfall types in dryland. A successive field experiment was also carried out for the planting density of spring maize from different cultivars in the dryland farming experimental station of Northwest A&F University in Heyang County, Shaanxi Province of China from 2013 to 2018. Taking the Yuyu22, Zhengdan958, and Xianyu335 as the experimental cultivars, four planting densities were set (D1: 52 500, D2: 67 500, D3: 82 500, and D4: 97 500 plant/hm2) to determine the yield traits at the harvest stage in each growing season. The results showed that the ear length and ear diameter of maize decreased with the increase of planting density, whereas, the length of tip back was on the rise. There were significant differences in the ear length and ear diameter among different rainfall types (P<0.05), where the overall performance was also ranked in the order of the wet year≥normal year > dry year, but the order of the length of tip back was the dry year > normal year≥wet year. The rainfall types posed significant effects on the yield traits, further to determine the grain yield of maize in dryland, indicating that the yield in the normal and wet years was significantly higher than that in the dry years (P<0.05), whereas, the yield stability was also higher in the normal and wet years than that of dry years. Furthermore, there were significant positive correlations of planting density on the ear number per square (P <0.05), whereas, the kernel number per ear and 100-seed weight presented a negative correlation with the planting density (P<0.05). The planting density and cultivar posed a significant influence on the grain yield, but the cultivars greatly varied in response to the planting density (P<0.05). Specifically, the suitable planting density of Yuyu22 was 52 500-67 500 plant//hm2, and Zhengdan958 and Xianyu335 were 67 500-82 500 plant/hm2. Moreover, the latter presented a more stable yield. The correlation analysis showed that the ears number per square and the number of the kernels per ear were the most important factors affecting the yield of spring maize in the dry years. In the normal and wet years, the ear number per square was the main factor under a low planting density (D1), whereas, the 100-seed weight of spring maize served as the main factor under a high planting density (D4). A relatively higher planting density with 67 500-82 500 plant/hm2 combined with the density-tolerance cultivar (Zhengdan958 and Xianyu335) can be widely expected to improve the grain yield and yield stability of dryland maize. The finding can provide for the optimal planting pattern in sustainable dryland agriculture.