Abstract
Humic acid (HA), not only promote the growth of crop roots, they can be combined with nitrogen (N) to increase fertilizer use efficiency and yield. However, the effects of HA urea fertilizer (HA-N) on root growth and yield of sweet potato has not been widely investigated. Xushu 28 was used as the experimental crop to investigate the effects of HA-N on root morphology, active oxygen metabolism and yield under field conditions. Results showed that nitrogen application alone was not beneficial for root growth and storage root formation during the early growth stage. HA-N significantly increased the dry weight of the root system, promoted differentiation from adventitious root to storage root, and increased the overall root activity, total root length, root diameter, root surface area, as well as root volume. HA-N thus increased the activity of superoxide dismutase (SOD), peroxidase (POD), and Catalase (CAT) as well as increasing the soluble protein content of roots and decreasing the malondialdehyde (MDA) content. HA-N significantly increased both the number of storage roots per plant increased by 14.01%, and the average fresh weight per storage root increased by 13.7%, while the yield was also obviously increased by 29.56%. In this study, HA-N increased yield through a synergistic increase of biological yield and harvest index.
Highlights
Plant roots are the main organ for crops to absorb nutrients and water, and they are the place where physiologically active substances, such as some amino acid and hormones are synthesized
Humic acid (HA), N, HA+N, and HA-N treatments increased the yield by 5.52%, 6.88%, 21.46%, and 29.56%, respectively
These results indicated that nitrogen increased yield by increasing the average fresh weight per storage root, while HA-N promoted both the number of storage root and the average fresh weight per storage root
Summary
Plant roots are the main organ for crops to absorb nutrients and water, and they are the place where physiologically active substances, such as some amino acid and hormones are synthesized. The morphology and physiological characteristics of roots affect growth, development and yield formation of crop [1,2,3,4]. Dysplasia or physiological dysfunction of plant roots will severely affect plant growth and development [5]. One of the main cultivation measures to increase yield of sweet potato is the application of nitrogen; nitrogen affects root growth and differentiation of sweet potato, and increasing yield [6]. A certain range of nitrogen application, the increase of nitrogen into the soil during the early growth stage can increase the total biomass of roots, while root total biomass differentiating to storage roots.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
