Page 118 - Nutrient Management Planning Guide

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Chapter 3.4

Soil testing labs may also make an adjustment for pulse crop stubble or manure application in the previous one or two years. Depending on yield, residues from previous pulse crops can release between 20 to 30 kg/ha of available N to the following crop. Likewise, release from the organic portion of the manure will increase the soil’s nitrogen supplying power for one or two years after application. This underscores the importance of providing complete information about management and manure application history for a field when submitting samples for analysis.

Soil Texture

Soil texture is the relative proportion of sand, silt and clay in a soil. As discussed in Chapter 2.1, texture directly affects soil water holding capacity, water infiltration rate and indirectly affects soil fertility through CEC.

Soils can be placed into groups (Table 3.4.10) based on textural class, which is determined using a mechanical analysis or the “hand feel” method (Figure 3.1.5, Chapter 3.1). The soil textural triangle is useful for classifying a sample based on the percent sand, silt and clay (Figure 3.1.4, Chapter 3.1).

Table 3.4.10 Soil Texture Group Based on Soil Texture Class

Soil Texture Group

Very Coarse Coarse Medium Fine Very Fine

Soil Texture Classes

Sand Loamy Sand

Sandy Loam Fine Sandy Loam

Loam Sandy Clay Loam Sandy Clay Clay Loam

Silt Loam Silty Clay Loam Silt

Clay Silty Clay Heavy Clay

Source: Kryzanowski et al. 1988

Table 3.4.11 Classifications for Organic Soils Based on Organic Matter Content

Classification Organic Matter Content (%)

Muck 30–45 Peaty Muck 45–65 Mucky Peat 65–85 Peat 85–100

Source: Landva et al. 1983

Available Soil Moisture

The amount of soil moisture available at the time of planting is an important consideration when making cropping and fertility decisions. Crop yield potential is directly related to stored soil water and growing season rainfall or irrigation. Low moisture availability will limit crop yield and reduce nutrient requirements. Soils are characterized as being dry, average or wet according to the depth of moist soil and texture class (Table 3.4.12).