BIOL 1120 REEDER
PLANT NUTRITIONAL REQUIREMENTS
I. Plant Requirements
A. Nutrients
1. Macronutrients (10)
a. Those required in large amounts: carbon, hydrogen, oxygen, nitrogen, phosphorus,
potassium, sulfur, calcium, magnesium, and silicon.
b. Used in quantities of up to one hundred to two hundred pounds per acre.
c. Sources:
1) C,H,O: come from water & gases
2) N from soil as ions of nitrogen salts: nitrate (NO3-) & ammonium (NH4-)
3) Commercial fertilizers rated by percentage of those needed in greatest quantities:
N,P,K; 5-10-5: 5% N, 10% P, 5% K by weight
4) Remaining nutrients derived from the soil as dissolved mineral ions.
2. Micronutrients (9)
a. Those required in smaller amounts: iron, boron, manganese, copper, molybdenum,
chlorine, zinc, sodium and nickel.
b. Derived from the soil as dissolved mineral ions.
3. Deficiencies
a. An inadequate supply of any one of these minerals may result in either general deficiency
symptoms (chlorosis that results in yellowing, paleness & poor growth) to more specific
symptoms (slow growth, stunting, small leaves, meristem death).
B. Soil
1. Minerals used by plants come ultimately from rock particles making up the soil.
2. Factors that influence the soil's nature: nature of the rock from which soil was derived,
climate of the region with weathering factors, characteristic life in and on the soil, the soil's
exposure, slope, & human activities.
3. Classified according to the rock particles average size comprising the soil: solid inorganic
portion.
a. Clay: finest particles (less than 0.002mm diameter)
b. Silt: larger (0.02 to 0.002mm)
c. Sand: largest (2 to 0.02mm)
4. The varying proportions of these particles determine the soil texture - with the percentage of
clay representing the most important fraction determining the soil's character.
a. Sands
b. Loams: typically 40% sand & silt, 20% clay; *represents the agriculturally important
soils.
c. Silts
d. Clays: at least 40% clay
5. The particle's size greatly influences the soil's capacity to hold soil water.
a. Amount of runoff, infiltration, & percolation into the soil can vary.
1) Runoff never penetrates the soil & may carry away valuable nutrients.
2) Amount of infiltration and percolation affects water available to plant life.
b. Water that remains in the soil is held by:
1) Capillary attraction resulting in capillary water: water held between particles against
the force of gravity.
bio1120_plant_nutritional_req.doc 4/3/09
