Soil Fertility and FertilizersByAllah Dad Khan

Soil Fertility and Fertilizers

• What is a fertilizer?– Definition - a material added to the garden

that supplies essential nutrients plants need for vegetative and reproductive growth.

• Why are fertilizers important?– Build-up - increasing the level of minerals

and OM in the soil.– Maintenance - replenishing nutrients lost

through leaching, removal during plant growth, and harvest

Fertilizers and pH

• Optimum soil pH is plant species dependent– Most plants will grow

well at pH 6.2-6.8– IL soils slightly acidic -

5.8-6.8

Slightly Tolerant(pH 6.5-6.8)

Moderately Tolerant(pH 5.5-6.8)

Very Tolerant(pH 5.0-6.8)

AsparagusBeetBroccoliCabbage

BeanCarrotCornCucumber

PotatoRhubarbSweet PotatoWatermelon

Fertilizers and pH

• pH influences nutrient availability– Determines nutrient form in soil– How strongly nutrients are bound to soil particles

• Nutrients deficient in acid soils– Ca, P, Mg, Mo

• Nutrients deficient in alkaline soils– Cu, Fe, Mn

Nutrient availability by pH

Adjusting pH

• Lime replaces H+ ions with Ca2+ ions• Amount applied depends on soil type and pH

change desired

Desired pH ∆ Sand Loam Silt Loam Clay Loam

4.5 6.55.5 6.56.0 6.5

----------------------Lbs/Acre of limestone------------------------

22001200600

580034001800

700040002200

840046002400