Page 58 - Nutrient Management Planning Guide

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Manure and Fertilizer as Sources of Nutrients and Potential Environmental Hazards

Manure

The following are some favourable characteristics of manure as a nutrient source:

In most cases, manure is available for free or •

minimal cost. However, trucking and application costs can minimize this advantage. Manure can serve as a soil conditioner through the •

addition of organic matter. This can improve the physical structure and stability of soils, particularly degraded soils and those with low organic matter. Manure has a broad profile of macro- and •

micronutrients; although, the nutrients are not balanced relative to crop requirements. Manure contains nutrients in organic and inorganic •

(crop available) forms. The organic form functions as a slow release fertilizer, gradually releasing nutrients to the crop. However, the uncertain timing of nutrient release relative to crop demand and the nutrient carryover to subsequent years can complicate soil fertility management.

Manure and Fertilizer as Potential Environmental Contaminants

Manure or fertilizer can boost soil fertility for crop production; however, both can also pose a potential environmental risk. Improper handling, storage and application of manure or fertilizer create a risk of contamination to soil, water, and air quality.

Risks to Soil Quality

Improper manure and fertilizer management can adversely affect soil quality in the following ways:

Livestock manure can be a rich source of soluble •

ions like sodium (Na + ) and potassium (K + ) because animals retain only a small amount of the salt they consume. Repeat applications of manure at rates

The impact of manure application on soil organic matter is influenced by the solids content of the manure (solid manure has a greater influence than liquid manure).

s i d e b a r exceeding agronomic requirements can contribute

to saline soil conditions. Long-term buildup of Na can also have a negative impact on soil structure by reducing soil particle aggregation. Frequent traveling by loaded application equipment •

on wet soils can lead to soil compaction. Soil particles are squeezed together by compaction, reducing pore spaces available for air and water storage. This can inhibit root growth and increase surface runoff.

Risks to Water Quality

When manure or fertilizer is improperly handled or applied at rates exceeding crop requirements, contaminants including nutrients and pathogens can enter surface water and groundwater.

Groundwater »

Groundwater is an important source of water for many rural Albertans. Manure and fertilizer application pose several risks to groundwater including contamination from N, P, and pathogens. Manure and nitrogen fertilizer applications raise soil nitrate (NO

3

- ) levels. Nitrate can leach into groundwater because it is soluble and mobile in soils. High-risk groups (e.g., infants and pregnant women) who consume water high in NO

3

- (i.e., above 10 ppm N or 45 ppm NO

3

- -N) have a reduced ability to transport oxygen in their bloodstreams. This condition is referred to as methemoglobinemia (“blue baby syndrome”).

Most soils in Alberta have a strong ability to adsorb (bind) P, which limits its entry into groundwater. However, leaching can occur when the soil’s adsorption capacity is saturated with high levels of P. This can happen from over-application of manure, particularly on coarse textured soils in high-rainfall or irrigated areas.

Transmission of manure pathogens to groundwater is rare, but can occur on coarse textured soils with high