PART 3 – ESSENTIAL NUTRIENTS
PHOSPHORUS
Phosphorus is an essential macronutrient contained in every living cell. It is involved in a number of physiological functions within the plant including:
a.Energy transformations within the plant in the form of adenosine triphosphate (ATP)
b.A constituent of the genetic material in the cell nucleus
c.Carbohydrate transformation such as the conversion of starch to sugar.
The quantity of phosphorus utilized by the turfgrass plant is considerably less than the amount of nitrogen and potassium.
Effects of Phosphorus
Phosphorus affects the:
a.Establishment
b.Rooting
c.Maturation
d.Reproduction of turfgrass
It is particularly vital during the seedling stage of turfgrass growth and development. Thus, phosphorus should be placed near the seed during planting to assure rapid establishment. It also stimulates root growth and branching.
Higher phosphorus levels hasten maturity, while phosphorus deficiency delays maturity. A phosphorus deficiency also causes a reduction in the tillering, shoot growth, and moisture content in turfgrass shoots.
Soil Relationships
Phosphorus is absorbed by the plant primarily as the H2PO4- ion. Phosphorus absorption is greatest at a soil pH of 6 – 7 and during periods of active plant growth.
POTASSIUM
Potassium is not a constituent of living cells but is essential in plant growth and developmental processes. Potassium functions in
a.Carbohydrate synthesis and translocation
b.Amino acid and protein synthesis
c.Catalyzing numerous enzymatic reactions including nitrate reduction
d.Regulating transpiration
e.Controlling the uptake rate of certain nutrients
f.Regulating the respiration rate
A potassium deficiency increases the respiration rate crossing a drain on the carbohydrate reserves. The transpiration rate of potassium deficient turfs is also higher. Turfgrasses require potassium in a relatively large amount, second only to nitrogen.
Effects of Potassium
Turf grasses may not exhibit a visual response to potassium in terms of shoot colour and density of growth. However, potassium does influents turfgrass
a.Rooting
b.Drought, heat, and cold hardiness
c.Disease proneness
d.Wear tolerance
Potassium regulates the absorption and retention of water by plants, which influences the heat, cold and drought hardiness of turf grasses.
Soil Relationships
Potassium is commonly absorbed as the K+ ion. The potassium content of soils varies considerably but is generally larger than the amount of phosphorus of nitrogen normally found.
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