Page 280 - Nutrient Management Planning Guide

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Cropping Practices to Reduce Nutrient Losses in Runoff

later in the season such as warm season crops, silage or fall cereals. Manure may also be applied to forage and pasture crops or injected between forage cuts. This increases the opportunity for manure application when the soil is drier reducing the risk of soil compaction while providing nutrients when needed the most. If manure must be applied in late summer or fall, select fields that are a low risk for snowmelt water runoff to reach surface bodies of water.

Incorporate or Inject Manure

The incorporation or injection of manure can reduce the exposure of manure to surface runoff events reducing the opportunity for dissolved nutrients to be carried from manured fields to adjacent bodies of surface water. In Alberta, manure must be incorporated within 48 hours of application unless it is applied to forage, reduced tillage systems or on frozen or snow covered ground (Chapter 4.4).

While incorporation does not fit well with perennial crops, direct seeding or no-tillage farming operations, the low disturbance liquid manure injection technologies have been shown to work well with these systems. Injection technologies allow for the direct placement of liquid manure into standing forages or stubble fields with minimal disturbance.

Alternatively, high disturbance tillage can be used to incorporate surface applied liquid or solid manure. Although tillage can be an effective means to incorporate manure, the negative consequences associated with tillage include reducing the amount of protective crop cover residue and the breaking up soil structure. The result can reduce the snow trapping ability of the field and lead to a greater risk of soil loss to erosion by water

and wind. However, some of the negative effects will be offset by manure application since organic matter in manure can protect the soil surface from erosion, promote water infiltration and improve soil structure.

Practices to Deal with Slope

The primary way to control runoff on problem slopes is to disrupt slope uniformity using practices such as farming on the contour or maintaining permanent ground cover. These practices generally work best on slight to moderate slopes (e.g., < 6 or 7 %) that are relatively uniform. For sites where runoff flow patterns are more concentrated, a combination of practices described in this chapter with more intensive constructed erosion control measures described in Chapter 8.3 may be required.

Farm on the Contour

Farming on the contour refers to performing field operations across the slope along the shape (or contour) of the land. This results in a series of small ridges and furrows that act as micro-terraces or obstacles to water attempting to flow down the slope. Field operations on the contour can be done to direct water flow toward an outlet such as a grassed waterway thereby providing additional runoff control and soil protection (Figure 8.2.1).

Generally, contour farming dramatically reduces erosion on gentle slopes but is less effective on steeper slopes. The presence of ground cover (e.g., standing crop residue) increases the effectiveness of contouring.