Page 47 - Nutrient Management Planning Guide

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Chapter 2.2

To contend with soil acidity, choose acid tolerant crops or consider liming the soil.

s i d e b a r Soil Fertility and Management Implications of pH

There are several ways that pH affects soil fertility and management:

Microorganisms involved in nutrient cycling are •

sensitive to large shifts in pH. Nutrient cycling is slowed or stopped if microbial populations are affected. Soil pH affects nutrient solubility and can alter the •

form and availability of nutrients (Figure 2.2.4). Under low pH conditions, some nutrients become less available to plants because their chemical structure changes (e.g., P). In other cases, nutrients become unavailable because they bind tightly to soil particles.

Source: AF

Figure 2.2.4 Nutrient Availability as Affected by pH

Low pH conditions reduce soil base saturation by •

displacing plant nutrients (e.g., Ca 2+ and K + ) from exchange sites with H + and soluble aluminum (Al 3+ ) ions. Nutrients displaced from exchange sites can be lost or leached from the system and are no longer available to plants. Plant species vary in their acidity tolerance •

(Figure 2.2.5). This is strongly influenced by a plant’s sensitivity to levels of soluble aluminum (Al 3+ ), which increases substantially under acidic conditions. Crops produced in soils outside their acidity •

tolerance range will result in reduced yields. Under acidic conditions, nutrient requirements should be adjusted on the basis of crop type and pH level for anticipated reduced yield potential.