Reduced 15N Losses by Winter and Spring Night-Warming Are Related to Root Distribution of Winter Wheat

Abstract

To develop efficient N management strategies for high wheat NUE and minimizing the environmental impact of N losses under asymmetric warming, 15 N micro-plot experiments were conducted to investigate the effects of night-warming during winter (warming by 1.47–1.56°C from tillering to jointing), spring (warming by 1.68–1.82°C from jointing to booting), and winter + spring (warming by 1.53–1.64°C from tillering to booting) on root growth and distribution of winter wheat, the fates of 15 N-labeled fertilizer, and their relationships in 2015–2017. The results showed that night-warming increased the recovery of basal 15 N and top-dressed 15 N, while reduced the residual and loss of basal 15 N and top-dressed 15 N. The losses decreases of top-dressed 15 N were higher than those of basal 15 N, indicating that night-warming reduced losses of fertilizer 15 N mainly by reducing losses of top–dressed 15 N. Moreover, pre-anthesis root dry matter accumulation rate in 0–60 cm soil layer were promoted, resulted in improved root biomass and root/shoot ratio, which favored increasing recovery of fertilizer 15 N and reducing losses of fertilizer 15 N. Furthermore, residual fertilizer 15 N content in 0–100 cm soil layer was reduced, which was associated with improved root weight density in 0–60 cm soil layer, resulted in reduced leaching losses of fertilizer 15 N. The path analysis showed that root dry matter distribution in 0–20 cm soil layer was the most important in contributing to reducing losses of total fertilizer 15 N compared with other soil layers. Two years data showed that winter and spring night-warming gave better root growth and distribution in 0–20 cm soil layer, resulted in reduced the losses of fertilizer 15 N and improved the recovery of fertilizer 15 N, while maximizing grain yield of winter wheat, and winter + spring night-warming resulted in higher advantages than winter night-warming and spring night-warming.

Morphology and Nitrogen Uptake and Distribution of Wheat Plants as Influenced by Applying Remedial Urea Prior to or Post Low-Temperature Stress at Seedling Stage

“…From our results of 15 N labelled urea amendment experiment, the percentage of total nitrogen from 15 N urea was more than 10% higher under N-LT than that under LT-N, indicating that nitrogen applied prior to low temperature better mitigated the injury of wheat roots caused by low-temperature stress (Table 3). Our finding was in agreement with the reports by Azam et al [37] and Hu et al [38], who reported that better roots were conducive to the absorption and utilization of soil nitrogen and fertilizer. These results further confirmed our hypothesis from the perspective of nitrogen uptake and utilization that nitrogen application prior to low-temperature stress was more beneficial to recover wheat growth, as compared with the nitrogen post low-temperature stress.…”

Fertilizer 15N balance in a soybean–maize–maize rotation system based on a 41-year long-term experiment in Northeast China

“…In our study, the residual fertilizer 15 N remained mainly in the top 20 cm soil though frequent rainfall occurred during the soybean and maize growing seasons. It might be attributed to the microbial immobilization and some adsorption of mineral N forms (presumably NH + 4 ) in exchangeable sites of the topsoil, in line with other studies (Liu et al, 2015;Karwat et al, 2017;Hu et al, 2019;). Inversely, higher fertilizer 15 N accumulated in the 20-40 cm soil layer in North Central China, indicating that more N leaching occurred than in our study (Quan et al, 2020).…”

“…The percentage of 15 N-urea taken up by soybean or maize (Ndff) was calculated as ( Hu et al., 2019 ):…”