Combined effects of rainfall pattern and fertilization on subsurface nitrogen transport and loss from sloped soil: a laboratory experiment

• Published in: Arabian journal of geosciences 2023, Vol.16 (1), Article 31
• Main Authors: Xie, Meixiang, Zhang, Pingcang, He, Yupu, Hong, Dalin
• Format: Article
• Language: English
• Subjects: Ammonia; Biological fertilization; Distribution; Earth and Environmental Science; Earth science; Earth Sciences; Fertilization; Fertilizers; Laboratories; Laboratory experimentation; Loam soils; Nitrogen; Nodes; Original Paper; Outflow; Pollution dispersion; Pore water; Precipitation; Rainfall; Rainfall intensity; Simulated rainfall; Slope; Soil; Soil contamination; Soil dynamics; Soil pollution; Soils; Spatial variations; Tanks; Transport; Water pollution
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-022-11087-1

Subsurface nitrogen (N) losses from sloped soils are closely linked to water pollution. Few studies have focused on N loss and transport dynamics subjected to intermittent rainfall and variable N distributions in soils. Laboratory experiments using soil tanks, loam soils, a slope of 10°, simulated rainfall, and observation nodes were conducted to evaluate subsurface transport and losses of ammonia nitrogen (NH 4 –N), nitrate nitrogen (NO 3 –N), and total nitrogen (TN) in response to N fertilization and rainfall pattern. The rainfall pattern consisted of 12 intermittent rainfall events of three different intensities (low [0.4 mm min −1 ], moderate [1 mm min −1 ], and high [1.8 mm min −1 ]). Four equidistant observation nodes were set near the bottom of backfilled soils along the slope direction. N fertilizer was applied uniformly at the soil surface to achieve a uniform N distribution in the soil in tank S. Nonuniform N distribution was achieved by applying higher amounts of fertilizer at two ends of the slope in tank C and a lower amount in the middle of the slope. The results showed that (1) subsurface outflow amounts accounted for only 10.4% of intraday rainfall and N loss loads correlated positively with loss concentrations; (2) NH 4 –N concentrations showed different fluctuating trends while NO 3 –N and TN concentrations showed significant declines under the two different fertilizer distributions in response to the intermittent rainfall events; (3) the nitrate loss concentrations from tank C were larger than those from tank S except at the 4th and 7th days. Nonuniform application of N fertilizer caused more temporal and spatial differences than the uniform fertilization in declining rates of pore water N concentrations; (4) subsurface N loss correlated positively with its distribution at the slope foot while negatively with rainfall intensity (RI) and flow discharge (FDI) under each rainfall event. Our results provide new insights into subsurface N transport and loss from sloped soils.