Influence Mechanisms of Rainfall and Terrain Characteristics on Total Nitrogen Losses from Regosol

Abstract

Abstract:The upper reach of the Yangtze River is an ecologically sensitive region where water loss, soil erosion, and nonpoint source (NPS) pollution are serious issues. In this drainage area, regosol is the most widely distributed soil type. Cultivation on regosol is extensive and total nitrogen (TN) has become a common NPS pollutant. Artificial rainfall experiments were conducted to reveal the influence mechanisms of rainfall and terrain on TN losses from regosol. The results showed that there were positive correlations between precipitations and TN loads but negative ones between precipitations and TN concentrations. Furthermore, negative correlations were more obvious on fields with slopes of 5 • and 25 • than on other slopes. With increasing rainfall intensity, TN loads rose simultaneously. However, TN concentration in runoff-yielding time presented a decline over time. As far as terrain was concerned, TN loads grew generally but not limitlessly when slopes increased. Similarly, TN concentrations also rose with rising slopes; upward trends were more obvious for steeper slopes. Furthermore, the initial runoff-yielding time became longer for steeper slopes and the differences under various rainfall intensity conditions diminished gradually.

A Guideline for Successful Calibration and Uncertainty Analysis for Soil and Water Assessment: A Review of Papers from the 2016 International SWAT Conference

“…5-Ding et al [29] showed that total nitrogen load increased with increasing slope in a Yangtze River-cultivated Regosol soil.…”

Effects of Hydrological Processes on Surface and Subsurface Nitrogen Losses from Purple Soil Slopes

“…However, relationships between the subsurface hydrological process and nutrient losses were less described in literatures. For purple sloped soils, previous studies about N losses highlighted effects of rainfalls on N losses, but no relation between water flow and N losses was revealed (Ding and Zhang, 2009;Ding et al, 2017;Zhu et al, 2009). Ding et al (2017) presented negative relations between TN loads in runoff and rainfalls.…”

“…For purple sloped soils, previous studies about N losses highlighted effects of rainfalls on N losses, but no relation between water flow and N losses was revealed (Ding and Zhang, 2009;Ding et al, 2017;Zhu et al, 2009). Ding et al (2017) presented negative relations between TN loads in runoff and rainfalls. They further noted that more N losses happened due to increased runoff from increasing rainfalls.…”

“…(Bechmann, 2014;Jia et al, 2007;Kumwimba et al, 2017;Panagopoulos et al, 2011). Nitrogen (N) losses from sloped soils also have become a serious problem restricting sustainable and ecological friendly developments of sloping farmlands (Diaz et al, 2010;Ding et al, 2017;Kahl et al, 2007). Understanding N, including ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N), and total nitrogen (TN) loss mechanisms, is essential for ecological sustainability and efficient agricultural production.…”

“…The slope gradient has been analyzed in many studies of N losses from purple soil slopes. Several studies showed that N losses correlated positively with slope gradients (Ding et al, 2017;Huo et al, 2013), while others found that N losses tended to increase initially and then decrease with increasing slope gradients (Ding and Zhang, 2009;Li et al, 2010).…”