SPATIAL CLUSTERS OF SUBSURFACE DRAINAGE WATER NO3-N LEACHING LOSSES

The use of water-saving irrigation techniques has been encouraged in rice fields in response to irrigation water scarcity. Straw return is an important means of straw reuse. However, the environmental impact of this technology, e.g., nitrogen leaching loss, must be further explored. A two-year (2017–2018) experiment was conducted to investigate the vertical migration and leaching of nitrogen in paddy fields under water-saving and straw return conditions. Treatments included traditional flood irrigation (FI) and two water-saving irrigation regimes: rain-catching and controlled irrigation (RC-CI) and drought planting with straw mulching (DP-SM). RC-CI and DP-SM both significantly decreased the irrigation input compared with FI. RC-CI increased the rice yield by 8.23%~12.26%, while DP-SM decreased it by 8.98%~15.24% compared with FI. NH4+-N was the main form of the nitrogen leaching loss in percolation water, occupying 49.06%~50.97% of TN leaching losses. The NH4+-N and TN concentration showed a decreasing trend from top to bottom in soil water of 0~54 cm depth, while the concentration of NO3−-N presented the opposite behavior. The TN and NH4+-N concentrations in percolation water of RC-CI during most of the rice growth stage were the highest among treatments in both years, and DP-SM showed a trend of decreasing TN and NH4+-N concentrations. The NO3−-N concentrations in percolation water showed a regular pattern of DP-SM > RC-CI > FI during most of the rice growth stage. RC-CI and DP-SM remarkably reduced the amount of N leaching losses compared to FI as a result of the significant decrease of percolation water volumes. The tillering and jointing-booting stages were the two critical periods of N leaching (accounted for 74.85%~86.26% of N leaching losses). Great promotion potential of RC-CI and DP-SM exists in the lower reaches of the Yangtze River, China, and DP-SM needs to be further optimized.

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The implications of lag times between nitrate leaching losses and riverine loads for water quality policy

Scientific Reports ◽

10.1038/s41598-021-95302-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

R. W. McDowell ◽

Z. P. Simpson ◽

A. G. Ausseil ◽

Z. Etheridge ◽

R. Law

Keyword(s):

Water Quality ◽

Mean Transit Time ◽

Lag Time ◽

Practice Change ◽

N Leaching ◽

N Losses ◽

Leaching Losses ◽

Nitrate N ◽

The Mean ◽

Lag Times

AbstractUnderstanding the lag time between land management and impacts on riverine nitrate–nitrogen (N) loads is critical to understand when action to mitigate nitrate–N leaching losses from the soil profile may start improving water quality. These lags occur due to leaching of nitrate–N through the subsurface (soil and groundwater). Actions to mitigate nitrate–N losses have been mandated in New Zealand policy to start showing improvements in water quality within five years. We estimated annual rates of nitrate–N leaching and annual nitrate–N loads for 77 river catchments from 1990 to 2018. Lag times between these losses and riverine loads were determined for 34 catchments but could not be determined in other catchments because they exhibited little change in nitrate–N leaching losses or loads. Lag times varied from 1 to 12 years according to factors like catchment size (Strahler stream order and altitude) and slope. For eight catchments where additional isotope and modelling data were available, the mean transit time for surface water at baseflow to pass through the catchment was on average 2.1 years less than, and never greater than, the mean lag time for nitrate–N, inferring our lag time estimates were robust. The median lag time for nitrate–N across the 34 catchments was 4.5 years, meaning that nearly half of these catchments wouldn’t exhibit decreases in nitrate–N because of practice change within the five years outlined in policy.

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A WETLAND TO IMPROVE AGRICULTURAL SUBSURFACE DRAINAGE WATER QUALITY

Transactions of the ASAE ◽

10.13031/2013.11068 ◽

2002 ◽

Vol 45 (5) ◽

Cited By ~ 7

Author(s):

P. S. Miller ◽

J. K. Mitchell ◽

R. A. Cooke ◽

B. A. Engel

Keyword(s):

Water Quality ◽

Subsurface Drainage ◽

Drainage Water

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Undersowing Italian ryegrass diminishes nitrogen leaching from spring barley

Agricultural and Food Science ◽

10.23986/afsci.5661 ◽

2000 ◽

Vol 9 (3) ◽

pp. 201-216 ◽

Cited By ~ 10

Author(s):

R. LEMOLA ◽

E. TURTOLA ◽

C. ERIKSSON

Keyword(s):

Spring Barley ◽

Peat Soil ◽

Drainage Water ◽

Italian Ryegrass ◽

Soil Tillage ◽

N Leaching ◽

Sand Soil ◽

Total N ◽

Water Well ◽

Water Spring

Nitrogen (N) leaching from spring barley with and without undersown Italian ryegrass was studied in Jokioinen, south-western Finland during five years (summer 1993spring 1998) in 1.7 m deep lysimeters (Ø0.9 m) filled to 1.1 m with clay, silt, sand and peat soil. Tillage was performed in mid- October or in May, before sowing of the barley and ryegrass for the next season. In the second, third and fourth years of the experiment, total N leaching from barley without undersown ryegrass was 15, 7.9,32 and 38 kg ha-1 y-1 in clay, silt, sand and peat soil, respectively. Undersowing reduced N leaching by 52,31,68 and 27%. The reduction in N leaching from clay and sand when barley was undersown with ryegrass was nearly the same as the increased total uptake of N (barley +ryegrass).In sand soil, ryegrass was able to diminish the NO 3-N concentration of the drainage water well below the limit for acceptable drinking water. Spring tillage reduced N leaching only on peat soil (16%). Slight competition between the main and the undersown crop was indicated by lower N contents of the barley yield.;

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