2007 Nutrient Management Protocol for Ontario Regulation 267/03 Made under the Nutrient Management Act, 2002

Part 9 - Common Land Application Requirements

Table of Contents

  1. Determination of Percentage of Crop Residue
  2. Minimum Depth to Groundwater

9.1 Determination of Slope

Determining the maximum sustained slope of the land is a necessary part of determining application rates and setbacks. As the maximum sustained slope increases (gets steeper), the risk of liquid manure runoff at or following the time of application increases, as does the risk of soil erosion that can carry phosphorus into surface water. It is required to determine the slope of the field, or part of field, if it is within 150 metres (493 feet) of surface water.

Maximum sustained slope is expressed as a percentage in the Regulation, rather than as degrees. Per cent maximum sustained slope is simply the change in elevation of the land over a horizontal distance of one hundred units. A field that drops half a foot in one hundred feet has a maximum sustained slope of 0.5%, which is quite flat. A field that drops 15 feet in one hundred feet has a maximum sustained slope of 15%, which is quite steep. To put this in context, the Ministry of Transportation recommends steep grade warning signs whenever the road grade exceeds 9% over a distance of 150 metres.

There are several methods to determine the maximum sustained slope of the land, including but not limited to:

  • topographic maps (for long, simple slopes);
  • hand held Clinometer;
  • transit;
  • Topographic Survey by a licensed Surveyor; or
  • survey grade GPS, with elevation measurement.

The choice of a particular method will depend on the level of precision required, and the resources available to determine the maximum sustained slope. More precise methods are generally more expensive. Visual estimation of maximum sustained slope may provide adequate precision in many cases, but more precise measurements will be required where maximum sustained slopes are near the break points between different maximum sustained slope classes.

9.2 Determination of Percentage of Crop Residue

In some circumstances, application of agriculture source materials to the soil without incorporation is allowed where at least 30% of the soil surface is covered with crop residue at the time of application. This is provided for in Part VI of the Regulation.

The percentage of crop residue cover can be determined using the rope transect method.

The material required is a light rope (about 8 m in length) with knots or other markings spaced along the rope at 15 cm intervals so that there are a total of 50 knots. This rope is laid out across the soil surface, preferably at an angle to the crop rows, and pulled slightly taut. The number of knots that are touching pieces of crop residue (minimum dimensions 2 mm by 2.5 cm) is counted. This number, when multiplied by two, is the per cent crop residue cover. This determination should be made a minimum of four times in different parts of the field, and the results averaged.

9.3Minimum Depth to Groundwater

Part VI of the Regulation prohibits the application of non-agricultural source material to land unless there is at least 30 centimetres of "unsaturated" soil at the surface of the land.

9.3.1 Procedures for Determining Unsaturated Soil Conditions

"Unsaturated", in relation to soil condition, refers to a soil water content that is less than 100 per cent of the total pore space, or is at a negative soil water pressure as determined using the following procedure:

  • dig a hole or remove a soil core to a 30 cm depth
  • observe whether water flows into the hole from the surrounding soil (this may take up to an hour in clay soils).

Water will only flow under saturated conditions, so if water is observed, the soil does not meet the applicable criteria for unsaturated soil.

For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 20 July 2007
Last Reviewed: 20 July 2007