Page 35 - Nutrient Management Planning Guide

31

Chapter 2.1

In Alberta, salinity problems are often caused by sulphate salt accumulation (gypsum and epsom salts).

s i d e b a r

Adapted from Jones and Jacobsen 2002b

Figure 2.1.10 Release and Fixation of Potassium from Micas and Layered Clays

Greater than 90 % of the total K in prairie soils exists as part of the parent minerals: mica and feldspar. Release of K from these parent minerals occurs at a rate far too slow to meet the needs of growing plants.

There are two ways K can be lost from the system: leaching and erosion. Potassium leaching can occur on coarse textured soils that receive above average precipitation. In Alberta, however, K leaching losses are usually low because of the high cation exchange capacity of most soils and the dry climate. Erosion is a more important route of K loss.

Sulphur

Soil S levels can vary considerably within regions and even within fields. The switch to longer or continuous cropping rotations, particularly those that include canola (a high S user), has increased the occurrence of S deficiencies in Alberta.

Sulphur is essential for the conversion of NO

3

- to NH

4

+ in plants, and the synthesis of plant proteins. Sulphur is an integral part of plant processes, including N fixation in legumes, synthesis and functioning of chlorophyll, and oil formation in canola.

Sulphur requirements of crops remain high from germination through to grain filling because it is required to support vegetative growth and grain formation.