Page 77 - Nutrient Management Planning Guide

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Field Assessment

Table 3.1.2 Physical and Chemical Characteristics of Organic Soils

Organic Soil Type

Fibre Content

Moisture Holding Capacity (% of dry weight)

Electrical Conductivity (dS/m)

pH

Total N (% by weight)

Sedge Peat Low 400-600 0.5 – 3.5 5.0 – 8.5 2.0 – 3.0 Moss Peat Very high 1000-1500 0.2 – 0.4 3.5 – 5.5 0.5 – 1.0

Source: AAFRD, 1985e

Management Implications »

The natural characteristics of organic soils present some challenges to agricultural production and nutrient management. Organic soils are often waterlogged during certain times of the year (e.g., spring) because they are associated with high water tables. As a result of these characteristics, organic soils experience greater nutrient losses through leaching and denitrification, and impeded crop establishment and early growth.

Organic soils are very high in organic matter; therefore, the carbon to nitrogen (C:N) ratio is large. This slows the release of N from organic matter to the point where N available for plant uptake can be limited. Organic soils are also prone to micronutrient deficiencies, particularly copper, which may reduce productivity.

If a field has small areas of organic soil and the organic layer is thin enough, it may be feasible to incorporate and mix it with the mineral layers below. This action will improve the balance of organic and mineral fractions in the surface soil layer and potentially increase the rate of decomposition. This action will not, however, affect the water table or the risk of waterlogging. If large areas of organic soil dominate a field, the cropping options are typically limited to more flood tolerant forages, such as Garrison creeping foxtail, reed canary grass and timothy.

Eroded Soils

Eroded soils are unproductive areas that form largely as a result of erosion or excessive cultivation. Topsoil is stripped from the surface exposing the dense, compact, low organic matter subsoil. Productivity on these areas may be low due to poor fertility and restrictive soil physical properties. Exposed subsoils will have little or no soil development and usually have elevated pH. Eroded areas are also susceptible to drought conditions due to their poor water holding capacity and limited permeability.

Management Implications »

Eroded soils have several problems that limit yield potential such as crusting, restricted root growth, limited water availability, low fertility and pH extremes (high or low).

The hard, compact nature of exposed subsoils can negatively impact yield potential by restricting root growth and surface crusting. Emerging plants have a difficult time pushing through the surface crust to access light and extending roots through the soil to reach nutrients. The compact nature also increases the bulk density of the soil, making it difficult for water to infiltrate and reduces water availability for crop growth.

more info

More information on practical management of erosion and eroded soils, check out these factsheets, which can be ordered from the AF Publications Office or searched by Agdex number on Ropin’ the Web:

AF. 1997. An introduction •

to water erosion control. Alberta Agdex 572-3.

AF. 1998. Emergency •

wind erosion control measures. Adgex 572-1.

AF. 1998. An introduction •

to wind erosion control. Agdex 572-2.

AF. 2002. Fertilizing eroded •

knolls. Agdex 541-2.