Soil Fertility, Soil Amendments, and Plant Nutrition

PLSC 211 - Lecture 4

what are the 3 major nutrients?

Nitrogen, Phosphorous and Potassium

Nitrogen

• normally produces most dramatic growth response

• typically needed in larger amounts than other nutrients

• constitutes greatest single nutrient input cost

• component of chlorophyll

how is the major source of nitrogen on farms given to crops?

through manufactured nitrogen fertilizer (urea)

how many applications of N is needed per growing season for grasses?

2

true or false: it is necessary to apply N to legumes

false

what percentage of a grass-legume mixture must the legume make up for it to be recommended that no N is applied?

30% or more

what are ways N can be lost?

• leaching

• denitrification

• volatization

phosphorous

• important for creation of food

• needed for seed and fruit formation

• proper root growth

• increases survival and growth of seedlings

• not leached from soil

potassium

• needed in relatively large amounts

• helps with cold hardiness

• important for stand longevity and rhizome production in Bermuda grass

• helps strengthen natural disease-resisting mechanisms

• leaching possible on sandy soils

calcium

promotes plant growth and strengthens walls

magnesium

promotes biochemical and physiological processes

sulfur

helps with photosynthesis

list the micronutrients

manganese, iron, boron, copper, molybdenum, chloride, zinc, nickel

what nutrient is essential for clover seedling establishment, growth and persistence in forage stands?

boron

true or false: all uncorrected nutrient deficiencies of forages will eventually show specific visual symptoms

true

chlorosis

nitrogen deficiency, yellowing of leaves, older leaves affected first

potassium deficiency

leaves may have yellow or purple tint, brown edges, wilting, poor fruiting

phosphorous deficiency

dark leaves, tip dieback, curled leaves

true or false: fertilizers are sold in many different formulations usually expressed as ratios

true

what do the ratios on fertilizer stand for?

they express percentages of N P K in fertilizer