The efficient use of radiation, water, and nitrogen uptake by low-nitrogen-tolerant broomcorn millet (Panicum miliaceum L.) increased grain yield in the Loess Plateau, China

Abstract

Abstract The development of highly productive, low-N-tolerant cultivars is important to facilitate green and sustainable agriculture. However, it is unclear how low-N-tolerant cultivars achieve high grain yields under field conditions. In this study, the physiology facilitating the strong growth and efficient resource use of four low-N-tolerant Panicum miliaceum L. cultivars was compared with two low-N-sensitive cultivars using low and typical N fertilization applications (0, 75, and 150 kg N ha−1) on the semiarid Loess Plateau, China in 2019 and 2020. Compared to normal N fertilization, low N fertilization treatments significantly decreased plant photosynthetic capacity by regulating leaf stomatal closing, resulting in reduced dry matter accumulation and transportation, growth inhibition, weakened resource utilization, and consequently, a 28.9% decrease in grain yield. Compared to the low-N-sensitive cultivars, the low-N-tolerant cultivars had improved growth, leaf photosynthetic capacity, and dry matter transportation. These improved physiological characteristics resulted in more effective resource capture in the low-N-tolerant cultivars. This included higher and more efficient radiation use (24.4% and 26.9%), water use (63.5% and 48.2%), and N uptake (37.0% and 33.7%) in 2019 and 2020, respectively. Furthermore, the low-N-tolerant cultivars had increased productivity, with higher grain yields (38.6-41.6%) and harvest index values (16.7-28.2%) under low N conditions in the two years of the study. Overall, the results of this study determined the effect of low N input on broomcorn millet productivity and illustrated the strategies by which low-N-tolerant cultivars increased grain yield in semiarid field conditions.