soil fert 1st test

Soil functions

Medium for plant growth

Regulate water

Recycle raw materials

Habit for soil organisms

Engineering medium

Water purification

Cultural heritage preservation

Is soil fertility equal productivity

No

Soil fertility

Management of soil nutrients and water

Climate factors effecting productivity

Precipitation

Air temp

Humidity

Solar radiation

Wind

Altitude/ latitude

Crop factors effecting production

Genetics

Rooting activity

Population density

Pests and diseases

Planting date

Water availability

Crop rotation

Soil factors effecting productivity

Organic matter cycling

Soil texture

Management

Cation exchange capacity

Rooting depth

Nutrient supply

Soil ph

Slope

Compaction

What is the most common soil stress

Lack of moisture

What management practices are used to get good crop production

Fixing soil ph

Available nutrients

Irrigation/ drainage

Cover crops

Tillage

Why do we fertilize

Limited supply of nutrients

Increasing demand for productivity

Limited arable land

Projected population increase

What 3 criteria make an essential element

Directly involved in nutrition of plant

A deficiency inhibits the plants lifecycle

Deficiency is specific to element and only correct by applying that element

What are the plant essential nutrients

C H O N P K FE Zi Mn Cu Boron Chloride molybdenum and nickel

What are the structural nutrients

O C H

What are the primary nutrients

NPK

What are the secondary nutrients

Sulfur (from irrigation)

Ca

Magnesium

four dynamic processes of nutrient availability

Additions- fertilizer, N fixation

Removals - leaching, crop removal, gaseous losses

Transfers- eluviation of OM or K-rich soils (goes between soil horizons)

Transformations- changes type that is unavailable to plants

What is the law of minimum

The weakest link breaks the chain

Why is soil fertility not a exact science

It’s influence by many uncontrollable factors

Ion exchange

Process where an anion or cation is exchanged for another anion or cation in soil solution

Why is CEC important

Most soils are negatively charged which attracts cations

4 typical cations

H K NH4 Na

List typical anions

NO3 Cl SO4 PO4

How are soil nutrients absorbed

Soil slurry

What do the structural nutrients (C O H) make

Simple sugars ( glucose fructose)

What is the composition of soil

25% water 25% air 45% minerals 5% organic matter

What nutrients are more mobile in the soil

anions

What are the 3 mode that nutrients reach roots surface

Root interception

Mass flow

Diffusion

What mechanism of nutrient uptake is the most precent of nutrients moved

Mass flow

Is most soil + or - charged

-

What is a colloid properties

Very large surface area

Usually have internal and external surface

Surface charge could be + or - but usually net negative

Adsorption of cations and water

2 distinct structural units of layer silicate clays (LSC)

Si tetrahedral sheets

Al octahedral sheet

What is a 2:1 LSC

2 tetrahedral, and one octahedral

Example: montmorillonite

What is 1:1 LSC

1 tetrahedral, and one octahedral example: kaolinite

What is 2:1:1 LSC

2 terrestrial and 1 octahedral and 1 chlorine

Ex: chlorite

What is isomorphic substitution

One Si or Al atom is replaced with another atom of the same size. This creates a negative charge because they are usually less of a positive charge

Different ways LSC get charge

PH dependent charge- OH groups on surface

Broken edges

Where does om get its charge

OH groups

What is CEC

The amount of cations a clay or soil can exchange

Factors that influence CEC

Surface area (higher is better)

Mineral type (more 2:1 is better)

SOM

How to total quantity of Cations found

Base + acid charges

What is units of CEC

Cmol/Kg

Base stat formula

(Ca+mg+K+na)/ CEC

Relationship between BS and soil PH

BS goes up so does PH

cations in lyotrophic series

Al+3 > H+ > Ca+2 > Mg +2 > K+ = NH4 > Na+

CEC formula

(Ppm/10*(mass per charge)

What causes acidity

Commercial N fertilizers- nitrification

Crop removal

Leaching of basic cations

Decomp of Organic residue

Dissolution of CO2 in soil water

What factors contribute to soil variability

Slope

Soil texture

SOM

Crop history

Tillage

Drainage

Leveling

What 3 preliminary questions should you ask before soil sampling

When

Is timeline important

Who

How many

Where are my samples going

When using a spade for sampling how much soil should u get

½ slice

How is acidity defined based on h+

The negative log of H

What soil is strongly acidic

5.1-5.5

What ph is consider neutral

6.6-7.3

What is the opitum soil ph

5.6 - 7.0

How does high ph affect microbial activity

Restricts it

What two elements can become toxic at low ph

Al and Fe

how does the rain fall effect work

rain combines with CO2 and draws in H+ ions making the soil acidic

How to does nitirification contribute to acidity

Ammonium mixes with O to create nitrite and H+

What does irrigation raise ph

Because the calcium carbonate in the water is released

What is reserve acidity?

Acidity neutralized by lime and can not be replaced

What is salt exchangeable acidity

It can be neutralized by lime and replaced by a unbuffered salt solution

What does water ph measure

Exchangeable acidity

What does buffer ph measure

Reserve acidity

Why does burned lime have a higher CCE

Because it is smaller particles and reacts quickly

Why is mesh size important

The smaller the particles the faster the work bc they have more surface area

What is the effectiveness of lime that passes a 100 mesh screen

100 percent

How to get Fineness rating

(%passing 10-%passing 60)*0.4+(%passing 60- %passing 100)*0.9 +%passing 100

How to Realize neutralizing value

(%CCE*Fr)*100

How to get adjusted lime rate

Recommended rate * 57/actual RNV

How to soil texture effect lime rates

Small particles equals more lime

Why is there no lime recommendations for irrigated rice with soil ph <5.4

The irrigation water will lime it

What forms of N are found in the environment

N2 N2O NO NH3

What forms of N are available to plants

NO3 (nitrate) NH4 (ammonium)

How much of earths atmosphere is made of N

78%

Why is N essential for plants

It is used to make proteins and large portion of chlorophyll

What is signs of N deficiency

Yellowing of old leaves first then newer growth

What is mineralization of N

The decomposition of organic material

Steps of mineralization

Ammonification and nitrification

What is immobilization

When microorganisms out compete plants for N usually when there is a high C:N ratio. (>30:1)

What bacterium is used in nirtification

Nitrosomonas turns NH4 to NO2 then Nitrobacter turns it to NO3

What does Nitrification need

Oxygen

Why is NO3 particularly susceptible to leeching

Because it’s an anion

Factors that contribute to denitrifaction

Favorable environment for microbial activity and anaerobic condition after NO3 is created

What happens in volatilization

NH4 is converted to NH3 (gas) in a wet soil condition by euryace. Urea is very susceptible

What are 3 common N ferts and prevents

Urea - 46%

Anhydrous ammonia- 82%

Ammonium nitrate- 33%

What does N-STaR

Nitrogen Soil test for Rice

Why is split application important

To make sure most of the N makes it to the plant and is not lost