GPT Cards ESS Exam 1

Give an example of an early fertility experiment conducted by an early scientist

Van Helmont grew a willow tree in soil and concluded mass came from water though later scientists showed nutrients were required

Did the Morrill Act or the Hatch Act set up experiment stations at land grant universities

The Hatch Act established experiment stations

Will more food production be needed in the future? Why?

Yes because population is rising and cropland per person is declining

Give an example of how quality of produce is impacted by fertility

Wheat protein increases with nitrogen

Sugar beets need low nitrogen for high sugar

Tomatoes with too much nitrogen make vines but little fruit

Explain how fertility practices have impacted crop yields

Fertility practices raised corn yields from 30 bushels per acre in the 1860s to over 200 bushels per acre today

Explain Liebigs law of the minimum

Plant growth is limited by the nutrient in shortest supply like the shortest stave in a barrel

Explain how yields have been improved or decreased

Yields improved by fertilizer mechanization and breeding but decreased by soil degradation erosion and overuse

On a yield response curve what do toxic deficient critical level and sufficient mean

Deficient shows visible symptoms

Hidden hunger shows no symptoms but yield loss

Critical level is 90 to 95 percent of maximum yield

Sufficient means more nutrient does not increase yield

Toxic means too much nutrient reduces yield or causes environmental harm

Explain nutrient sufficiency

It is the level of nutrient where adding more will not increase yield

Explain the science of soil fertility

Soil fertility is the ability of soil to supply nutrients through processes like uptake leaching volatilization fixation and microbial conversions

Explain how top yields and maximum economic benefit may not be related

Maximum yield costs too much fertilizer while economic optimum is where profit is highest not yield

Explain cation exchange capacity

CEC is the soils ability to hold positively charged ions such as calcium potassium magnesium and ammonium

What is isomorphous substitution

It is when one ion replaces another of similar size in clay minerals creating permanent negative charge

Do 2:1 or 1:1 clays have pH dependent charge

1:1 clays have more pH dependent charge while 2:1 clays have mostly permanent charge

Explain pH dependent charge and where soils with lots of it are found

pH dependent charge comes from ionization of functional groups It is common in tropical soils like oxisols and ultisols

Explain buffering capacity

It is the ability of soil to resist changes in pH High CEC means strong buffering

Explain how ions move into plants

Through diffusion mass flow and root interception

Do mycorrhizae have a bigger impact on medium or low testing soils

They have a bigger impact on low testing soils

What two forms of nitrogen are referred to as available forms

Ammonium NH4 plus and nitrate NO3 minus

What are the three components of the nitrogen cycle

Mineralization nitrification and denitrification

Define mineralization immobilization and nitrification

Mineralization is organic nitrogen to ammonium Immobilization is microbes using nitrogen Nitrification is ammonium to nitrate

Why is carbon to nitrogen ratio important in nitrogen cycling

High C to N ratio causes immobilization Low C to N ratio promotes mineralization

What two bacteria are needed for nitrification

Nitrosomonas and Nitrobacter

Explain the conditions needed for denitrification

Anaerobic waterlogged soils with nitrate and a carbon source

What are the pathways by which nitrogen can be lost from soil

Leaching volatilization denitrification runoff and harvest removal

Explain eutrophication

Nutrient runoff causes algal blooms that deplete oxygen and create dead zones

Explain ways to minimize negative impacts from nitrogen fertilization

Use split applications cover crops buffer strips correct timing and avoid overapplication

Draw the nitrogen cycle

Nitrogen moves between organic matter ammonium nitrate gases and plants through mineralization nitrification denitrification and fixation

Explain plant uses for nitrogen

It is used for proteins nucleic acids and chlorophyll

Explain what nitrogen deficiency looks like

Yellowing or chlorosis on older leaves because nitrogen is mobile

Give examples where excess nitrogen has no effect and where it reduces yield

No effect when already sufficient Negative effect when it causes lodging delays maturity lowers sugar in beets or reduces tomato fruiting

How much nitrogen is available per acre in the atmosphere

About 35000 tons of nitrogen gas are above each acre but plants cannot use it without fixation

What is a symbiotic relationship

A mutual benefit such as Rhizobium bacteria fixing nitrogen for legumes

Explain factors important to mineralization and nitrification

Temperature moisture oxygen C to N ratio and microbial activity

Explain the nitrogen pathway in corn stalk decomposition

High C to N stalks first immobilize nitrogen then later mineralize it as microbes finish decomposition

Explain the factors important in nitrogen mineralization rates

Temperature moisture substrate quality and microbial activity

Why are harvest nitrogen losses permanent

Nitrogen in grain is removed from the field and does not recycle

Explain how gaseous nitrogen losses occur

Through denitrification to N2 or N2O and volatilization to NH3