Page 74 - Nutrient Management Planning Guide

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Chapter 3.1

Soil pH

In Alberta, acid soils occur frequently in the central Peace River regions (Figure 3.1.11). Alkaline soils are more common in the Brown and Dark Brown soil zones and on eroded hilltops.

Adapted from Kryzanowski, 1996

Figure 3.1.11 Occurrence of Acid Soils in Alberta

Since pH can vary considerably within individual fields, regional generalizations about soil pH conditions are not adequate for site-specific nutrient management. As such, field specific determination of pH is important. If pH is identified as a problem, a detailed sampling strategy can be used to determine the extent and severity of pH problems within the field.

Management Implications »

Soil pH should be considered when making management decisions for a number of reasons:

Extreme pH conditions will limit crop growth unless •

tolerant crops are selected. Most crops prefer pH in the neutral range (pH 6.5 to 7.0). Acidic conditions reduce the rate of organic matter •

decomposition, which affects the rate of nutrient release from organic sources. Alkaline or acidic soil conditions can reduce nutrient •

availability (see Figure 2.2.4, Chapter 2.2). Nutrient management planning should factor in reduced crop yield potential and nutrient availability on acid or alkaline soils. Soil pH reduces the rate of breakdown of some •

herbicide residues. This could result in herbicide injury to sensitive crops following in rotation. Therefore, when planning crop rotations consider possible herbicide carry over. At elevated soil pH (greater than 7.5), the natural •

equilibrium between ammonium (NH

4

+ ) and ammonia (NH

3

) shifts in favor of NH

3

, which can be lost by volatilization. Therefore, incorporation of broadcast manure and fertilizer is critical on high pH soils to minimize NH

3

losses. Nodulation of many legume crops is impaired in •

low pH soils. This reduces the amount of N fixed by the crop and increases the need for supplemental N inputs.

more info

For more information on managing acid soils, check out these factsheets, which can be ordered from the AF Publications Office or searched by Agdex number on Ropin’ the Web:

1996. Liming acid •

soils. Agdex 534-1.

2002. Wood ash: An •

alternative liming material for agricultural soils. Agdex 534-2.