Winter and spring night-warming improve root extension and soil nitrogen supply to increase nitrogen uptake and utilization of winter wheat (Triticum aestivum L.)

Elucidating the effects of asymmetric warming during winter and spring will help develop a feasible crop management strategy for climate change. Field experiments were conducted using the Yangmai-13 (vernal type) and Yannong-19 (semi-winter type) winter wheat cultivars to investigate the effects of night-warming during winter (warming by 1.47-1.53 °C from tillering to jointing), spring (warming by 1.68-1.77 °C from jointing to booting), and winter + spring (warming by 1.53-1.60 °C from tillering to booting) on plant growth and N utilization in 2014-2016. The results showed that the grain yield, N agronomic efficiency (NAE), and N recovery efficiency (NRE) of both cultivars were highly increased in response to night-warming, which were associated with enhanced dry matter and N accumulation, and winter + spring night-warming resulted in greater increases than winter night-warming and spring night-warming. Furthermore, the increase in pre-anthesis N accumulation was much higher than after anthesis, resulting in a greater increase in post-anthesis dry matter accumulation due to more leaf N distribution at anthesis to support photosynthetic production. Root growth characteristics (i.e., root length, surface area and volume, and root bleeding intensity) were significantly promoted, which favored plant N uptake. Soil urease and protease activity as well as the net N mineralization rate, which are involved in soil N supply capacity, were increased, whereas soil inorganic N content and apparent N surplus were clearly decreased, which indicated that plant N uptake capacity was highly improved in response to night-warming conditions. In conclusion, winter and spring night-warming improve pre-anthesis root growth and N uptake ability to promote plant growth, resulting in increased N utilization efficiency with reduced N fertilizer loss, and winter + spring night-warming has more advantages for N uptake and utilization of winter wheat.