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Technical Thematic Report No. 15. -Trends in residual soil nitrogen for agricultural land in Canada, 1981 2006

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Trends in residual soil nitrogen for agricultural land in Canada, 1981 2006

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C.F. Drury, J.Y. Yang and R. De JongFootnotea

Canadian Biodiversity: Ecosystem Status and Trends 2010
Technical Thematic Report No. 15
Published by the Canadian Councils of Resource Ministers

Library and Archives Canada Cataloguing in Publication

Trends in residual soil nitrogen for agricultural land in Canada, 1981-2006.

Issued also in French under title:
Tendances de l’azote résiduel dans le sol pour les terres agricoles du Canada, de 1981 à 2006.
Electronic monograph in PDF format.
ISBN 978-1-100-19925-2
Cat. no.: En14-43/15-2011E-PDF

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This report should be cited as:

Drury, C.F., Yang, J.Y. and De Jong, R. 2011. Trends in residual soil nitrogen for agricultural land in Canada, 1981-2006. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 15. Canadian Councils of Resource Ministers. Ottawa, ON. iii + 16 p.

© Her Majesty the Queen in Right of Canada, 2011
Aussi disponible en français

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Footnotes

Footnote a

All authors are with Agriculture and Agri-Food Canada

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Preface

The Canadian Councils of Resource Ministers developed a Biodiversity Outcomes FrameworkFootnote1 in 2006 to focus conservation and restoration actions under the Canadian Biodiversity Strategy.Footnote2 Canadian Biodiversity: Ecosystem Status and Trends 2010Footnote3 was a first report under this framework. It assesses progress towards the framework’s goal of “Healthy and Diverse Ecosystems” and the two desired conservation outcomes: i) productive, resilient, diverse ecosystems with the capacity to recover and adapt; and ii) damaged ecosystems restored.

The 22 recurring key findings that are presented in Canadian Biodiversity: Ecosystem Status and Trends 2010 emerged from synthesis and analysis of technical reports prepared as part of this project. Over 500 experts participated in the writing and review of these foundation documents. This report, Trends in residual soil nitrogen for agricultural land in Canada, 1981-2006, is one of several reports prepared on the status and trends of national cross-cutting themes. It has been prepared and reviewed by experts in the field of study and reflects the views of its authors.

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Acknowledgements

We would like to express our appreciation to Dr. E.C. Huffman and Dr. Xueming Yang for providing N coefficient data. We are also very grateful to the National Agri-Environmental Health Analysis and Reporting Program (NAHARP) for funding this research. Finally, we’d like to thank the reviewers of this report.

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Ecological Classification System – Ecozones+

A slightly modified version of the Terrestrial Ecozones of Canada, described in the National Ecological Framework for CanadaFootnote4, provided the ecosystem-based units for all reports related to this project. Modifications from the original framework include: adjustments to terrestrial boundaries to reflect improvements from ground-truthing exercises; the combination of three Arctic ecozones into one; the use of two ecoprovinces – Western Interior Basin and Newfoundland Boreal; the addition of nine marine ecosystem-based units; and, the addition of the Great Lakes as a unit. This modified classification system is referred to as “ecozones+” throughout these reports to avoid confusion with the more familiar “ecozones” of the original framework.Footnote5

Ecological classification framework for the Ecosystem Status and Trends Report for Canada.

Map

Long Description for Ecosystem Status and Trends Report for Canada

This map of Canada shows the ecological classification framework for the Ecosystem Status and Trends Report, named “ecozones+”. This map shows the distribution of 15 terrestrial ecozones+ (Atlantic Maritime; Newfoundland Boreal; Taiga Shield; Mixedwood Plains; Boreal Shield; Hudson Plains; Prairies; Boreal Plains; Montane Cordillera; Western Interior Basin; Pacific Maritime; Boreal Cordillera; Taiga Cordillera; Taiga Plains; Arctic), two large lake ecozones+ (Great Lakes; Lake Winnipeg), and nine marine ecozones+ (North Coast and Hecate Strait; West Coast Vancouver Island; Strait of Georgia; Gulf of Maine and Scotian Shelf; Estuary and Gulf of St. Lawrence; Newfoundland and Labrador Shelves; Hudson Bay, James Bay and Fox Basin; Canadian Arctic Archipelago; Beaufort Sea).

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Agri-environmental Indicators

As part of the National Agri-Environmental Health Analysis and Reporting Program, Agriculture and Agri-Food Canada has developed a suite of science-based agri-environmental indicators. These were first reported in 2000 (for 1981 to 1996), updated in 2005 (for 1981 to 2001), and most recently reported in 2010 (for 1981 to 2006) (Eilers et al., 2010). Three of these indicators are presented by ecozone+ as part of the Technical Thematic Report Series for Canadian Biodiversity: Ecosystem Status and Trends 2010. They are soil erosion on cropland (McConkey et al., 2011), wildlife habitat capacity (Javorek and Grant, 2011), and this report on residual soil nitrogen.

All three of these agri-environmental indicators use data from the Canadian Census of Agriculture database. This database categorizes the agricultural landscape into four main cover types: Cropland, Pasture (broken down into Improved and Unimproved Pasture), Summerfallow, and All Other Land (All Other Land includes, for example, barnyards, woodlots, lanes, windbreaks, marshes, and bogs) (Huffman et al., 2006; Statistics Canada, 2008). The soil erosion and residual soil nitrogen Technical Thematic Reports focus on the agricultural land in production and therefore only use the first three cover types in their calculations (Unimproved Pasture is not included in the soil erosion analysis). Javorek and Grant (2011), on the other hand, include the All Other Land cover type when reporting on wildlife habitat capacity on agricultural land. The definition of “Cropland” in the soil erosion report differs from that used by the Canadian Census of Agriculture in that it includes the Census of Agriculture categories of Cropland, Improved Pasture, and Summerfallow when referring to “Cropland”. For these reasons, numbers presented for the total amount of agricultural land or Cropland or proportions of different cover types for an ecozone+ or region may differ slightly between the three agricultural reports prepared as part of the Technical Thematic Report Series for Canadian Biodiversity: Ecosystem Status and Trends 2010. Additional discrepancies may exist due to the methodology used to maintain anonymity of the data (see Eilers et al., 2010 for more information).

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Introduction

The Residual Soil Nitrogen (RSN) Indicator is an estimate of the amount of inorganic nitrogen that remains in the soil per hectare after crops are harvested (Drury et al., 2010). Most of the inorganic nitrogen remaining in the soil after harvest is in the form of nitrate (NO3-) but it can also include ammonium and trace amounts of nitrite. High RSN levels can occur when crop yields are lower than expected or when fields receive more fertilizer or manure than needed for crop production. Yield reduction leading to high RSN levels can occur as a result of many factors, including, adverse climatic conditions (for example, insufficient or excess precipitation, or early or late frost), disease, insects, or from poor soil quality (for example, compact soils, poor aeration, or degraded structure). The RSN present in the soil after harvest can leach out of the crop root zone, particularly in humid areas where precipitation is typically greater than evaporation. High levels of nitrate in excess of the National Agri-Environmental Standards Initiative recommended Ideal Performance Standards of 4.7 mg nitrogen per litre (N/L) for freshwater can be harmful to the environment (Guy, 2008; Guy, 2009) and nitrate levels in both surface and groundwater in excess of the drinking water guidelines can be harmful to livestock and humans when this water is used for potable consumption (Chambers, 2001). Further, in wet soil conditions, nitrate is subject to denitrification loss which reduces nitrate to nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2) (Drury et al., 1992). Although NO and N2O emissions have a negative impact on air quality, these gaseous losses reduce the amount of residual nitrate in the soil which can potentially be leached out of the root zone and can therefore reduce risk to water contamination. In regions where leaching and denitrification losses are low, RSN may remain in the root zone and can be available to the subsequent crop. Therefore, estimating RSN in soils is useful to identify the agronomic regions that are at medium to very high risk of accumulating nitrate in the fall which may leach into the groundwater or be denitrified and impact air quality. It is also useful to track the changes in RSN levels in the soil over time in order to observe whether the risk of nitrate accumulation in soils is increasing, decreasing, or remaining steady. In regions with elevated RSN levels, management practices can be adopted to reduce the amount of RSN in the soil which can be both economically and environmentally beneficial.

Nitrate concentrations in water have been found to affect biodiversity. The short term freshwater exposure limits (49 mg N/L or 218 mg NO3-/L) for Canada were based on LC50 values for the nitrate concentrations which were toxic to a range of invertebratess (such as, caddisfly and water flea), fish species (such as, channel catfish, lake whitefish, bluegill, rainbow trout, and chinook salmon), as well as amphibians (such as, Pacific tree frog and African clawed frog) (Guy, 2008). The long term exposure limits to nitrate in freshwater were also obtained based on LC10 values and maximum acceptable toxicant concentration values for a range of fish, amphibians and invertebrates and the recommended National Agri-Environmental Standards Initiative Ideal Performance Standard was established at 4.7 mg N/L or 21 mg NO3-/L (Guy, 2009). Nitrate concentrations of 6.25 and 25 mg N/L were reported to have sublethal effects on embryo development rates as well as the fry body size of lake trout and lake whitefish (Mcgurk et al., 2006). These concentrations can be in the range of concentrations of tile drainage water being released from agricultural land (Drury et al., 2009; Drury et al., 2010). High concentrations of nitrate, ammonia, and/or phosphate have also been implicated in the formation of algal blooms (Chambers et al., 2001).

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Footnotes

Footnote 1

Environment Canada. 2006. Biodiversity outcomes framework for Canada. Canadian Councils of Resource Ministers. Ottawa, ON.p. Environnement Canada. 2006.

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Footnote 2

Federal-Provincial-Territorial Biodiversity Working Group. 1995. Canadian biodiversity strategy: Canada's response to the Convention on Biological Diversity. Environment Canada, Biodiversity Convention Office. Ottawa, ON. 80 p.

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Footnote 3

Federal, Provincial and Territorial Governments of Canada. 2010. Canadian biodiversity: ecosystem status and trends 2010. Canadian Councils of Resource Ministers. Ottawa, ON. vi + 142 p.

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Footnote 4

Ecological Stratification Working Group. 1995. A national ecological framework for Canada. Agriculture and Agri-Food Canada, Research Branch, Centre for Land and Biological Resources Research and Environment Canada, State of the Environment Directorate, Ecozone Analysis Branch. Ottawa/Hull, ON. 125 p. Report and national map at 1:7 500 000 scale.

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Footnote 5

Rankin, R., Austin, M. and Rice, J. 2011. Ecological classification system for the ecosystem status and trends report. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 1. Canadian Councils of Resource Ministers. Ottawa, ON.

Return to reference5

Introduction