Runoff nitrogen (N) losses and related metabolism enzyme activities in paddy field under different nitrogen fertilizer levels
2018
Wang, Junli | Fu, Zishi | Chen, Guifa | Zou, Guoyan | Song, Xiangfu | Liu, Fuxing
Nitrogen (N), one of the most important nutrients for plants, also can be a pollutant in water environments. N metabolism is sensitive to N fertilization application and related to rice growth. Different levels of N fertilization treatment (N0, control without N fertilizer application; N100, chemical fertilizer of 100 kg N ha⁻¹; N200, chemical fertilizer of 200 kg N ha⁻¹; N300, chemical fertilizer of 300 kg N ha⁻¹) were tested to investigate N loss due to surface runoff and to explore the possible involvement of rice N metabolism responses to different N levels. The results indicated that N loss through runoff and rice yield was simultaneously increased in response to increasing N fertilizer levels. About 30% of total nitrogen (TN) was lost in the form of ammonium (NH₄⁺) in a rice growing season, while only 3% was lost in the form of nitrate (NO₃⁻). Higher N application increased carbon (C) and N content and increased nitrate reductase (NR) and glutamine synthetase (GS) activities in rice leaves, while it decreased glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) activities. These results suggest that N caused the accumulation of assimilation products in flag leaves of rice and stimulated N metabolic processes, while some protective substances were also stimulated to resist low N stress. This study provides a theoretical basis for improving N fertilizer management to reduce N loss and increase rice yield.
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