NITRATE (NO3-) RELEASE, TRANSPORT AND ATTENUATION INTO SOILS FROM AGRICULTURAL ACTIVITIES

Nitrate (NO3-) Release, Transport And Attenuation Into Soils From Agricultural Activities



Table of Contents

Nitrate (NO3-) Release, Transport And Attenuation Into Soils From Agricultural Activities4

1. Introduction4

2. Methods6

2.1. Study site6

2.2. Sample assemblage and analysis8

2.3. DOM removal8

2.4. Nitrate isotopes9

2.5. Vegetation isotopes and sampling9

3. Results10

3.1. Nitrate concentrations10

3.2. Nitrate isotope ratios11

3.3. Vegetation d15N values13

4. Discussion14

4.1. Nitrate attenuation in wetland14

4.2. Denitrification enrichment factor16

5. Summary18

References20

Nitrate (NO3-) Release, Transport And Attenuation Into Soils From Agricultural Activities

1. Introduction

Under natural situation, nitrogen (N) is normally growth-limiting component in terrestrial ecosystems (Tamm, 1991). Annual inputs of new N (deposition, fixation, and inorganic weathering) are often insufficient to rendezvous yearly biological obligations and thus timber plantations have developed effective procedures of recycling accessible N (Rosswall, 1976). Forest collection and other disturbances usually outcome in decrease of N from catchments by decoupling means to blame for taut interior N biking (Vitousek, 1981). These deficiency can sway plantation regeneration time and species composition as well as affecting downstream aquatic schemes (Vitousek et al., 1979). Consequently, destiny of N is especially significant when contemplating biogeochemical penalties of plantation administration practices.

Fig. 1. The Turkey Lakes Watershed, Ontario, Canada.

 Stream trials for nitrate isotope investigation have been assembled frequently at weirs at catchment outlets since 1995. In May 1999, added trying along extent of stream in clear-cut catchment disclosed a decline in nitrate concentrations through a little wetland established in top part of catchment. Studies analyzing wetland answers to collection have concentrated on consequences of harvesting wetland itself (e.g. Shepard, 1994) or on riparian zone adjacent to aquatic environments (e.g. Broadmeadow and Nisbet, 2004). A large body of publications furthermore agreements with consequences of draining peatlands to enhance plantation development (e.g. Paavilainen and Päivänen, 1995). We are not cognizant of preceding investigations that have enquired wetland attenuation of elevated nitrate concentrations initiated by harvesting of adjacent uplands.

 

2. Methods

2.1. Study site

Biogeochemical study was started at TLW in 1980 to enquire consequences of acidic deposition on an acid-sensitive Canadian Shield ecosystem (Jeffries et al., 1988; www.tlws.ca). The TLW (47°03'N, 84°24'W; Fig. 1) is a 10.5 km2 watershed encompassing a sequence of five lagoons that finally drain into Lake Superior. Basin soils are Humo-Ferric podzols (Canada Soil Survey Committee, Subcommittee on Soil Classification, 1978) evolved from slim glacial till underlain by Precambrian silicate greenstone bedrock and secondary occurrences of granite (Semkin and Jeffries, 1983). Elevation varieties from 630 m at peak of Batchawana Mountain to 340 m at watershed outlet.

The temperate weather of locality is moderated by basin's proximity to Lake Superior. The TLW usually obtains 1200-1300 mm of precipitation every year (Sirois et al., 2001) with roughly 35% made a down fee as snowfall (Semkin et al., 2002). Seasonal mean temperatures variety from +17 °C in summer (July) to -13 °C in winter (January; Foster et al., 1992a). The vegetation of TLW basin is uneven-aged, mature to over-mature plantation overridden by sugar maple (Acer saccharum, 82% of basal area). Most of residual trees comprise of other hardwoods (Morrison, ...