What are the features of fertile soil?

Question 1

How does fertile soil affect water content?

Answer 1

• fertile soil allows good drainage ( doesn’t become waterlogged but still retains enough water for survival of soil biota )

Question 2

How does fertile soil affect soluble materials?

Answer 2

• contain macronutrients ( nitrogen and potassium ) present in ionic form ( nitrates and potassium ions )
• contain micronutrients ( copper and iron )
• toxic ions ( aluminium and heavy metals ) are adsorbed onto surface of mineral particles

Question 3

Explain the behaviour of hygroscopic water between soil particles?

Answer 3

• held by adhesive forces on the mineral particle

- cannot by absorbed by plants

Question 4

Explain the behaviour of capillary water between soil particles?

Answer 4

• water held by soil particles does not drain from the soil

- water can be absorbed by plants

Question 5

Explain the behaviour of gravitational water between soil particles?

Answer 5

• water can be absorbed by plants

- water drains easily

Question 6

How does fertile soil affect air content?

Answer 6

• most living organisms that increase fertility are aerobic

- well aerated soils are likely to be more fertile

Question 7

How does fertile soil affect dead organic matter?

Answer 7

• has a high dead organic matter content
• releases plant nutrients as it decomposes
• increase water retention
• provides food for soil biota

Question 8

How does fertile soil affect the pH?

Answer 8

• ranges from pH5.5 to pH7.0
• this is the range of tolerance for most plants and other soil biota
• acidic soils can increase leaching of plant nutrients
• acidic soils damage root cell membranes
• under alkaline conditions phosphates become insoluble

Question 9

How does fertile soil affect soil biota?

Answer 9

• detritivores ( beetle larvae ) break up dead organic matter and release nutrients into soil
• detritivores increase soil drainage and aeration by creating tunnels in the soil
• decomposers ( bacteria and fungi ) break down dead organic matter
• decomposers secrete digestive enzymes
• nitrogen-fixing bacteria convert gaseous nitrogen into ammonium ions
• mycorrhizal fungi - symbiotic relationship

Question 10

How does fertile soil affect the soil texture?

Answer 10

• soil texture is the property controlled by the promotions of the different size categories of mineral particles in the soil
• clay = <0.002
• silt = 0.002 - 0.02
• sand = 0.02 - 2.0

Question 11

Compare drainage rate in sandy and clay soils

Answer 11

SANDY - larger pore spaces allow rapid drainage which reduces the water content but increases aeration
CLAY - poorly drained

Question 12

Compare capillary action in sandy and clay soils?

Answer 12

SANDY - no capillary rise of water

CLAY - tiny pore spaces between particles allow water underground to rise towards surface

Question 13

Compare aeration in sandy and clay soils

Answer 13

SANDY - pore spaces in well-drained sandy soils are filled with air
CLAY - more likely to be waterlogged with a low aeration rate

Question 14

Compare nutrient retention in sandy and clay soils

Answer 14

SANDY - nutrient ions don’t adsorb easily onto sand particles
CLAY - nutrient ions adsorb easily onto clay particles

Question 15

Compare thermal capacity in sandy and clay soils

Answer 15

SANDY - lower thermal capacity ( warms up more rapidly after cold weather )
CLAY - high thermal capacity ( high water content - warm up and cool down slowly )

Question 16

Compare root penetration in sandy and clay soils

Answer 16

SANDY - easier
CLAY - particles are held together by capillary water on particle surfaces ( making it harder for plant roots to force their roots between soil particles )

Question 17

Compare ease of cultivation in sandy and clay soil

Answer 17

SANDY - lack of adhesion between particles make sit easier to cultivate them
CLAY - harder to

Question 18

What is the mix of sand, silt and clay in loam soils?

Answer 18

40:40:20

Question 19

Explain soil structure

Answer 19

• particles are bound together by polysaccharide gums ( produced by decomposition, by roots and action of soil biota )

Question 20

What are crumb peds?

Answer 20

• small and round
• produce good drainage, aeration and easy root penetration
• improve soil fertility

Question 21

What are platy peds?

Answer 21

• large and flat
• reduces drainage, aeration and root penetration
• produce less fertile soils

Question 22

How does fertile soil affect soil depth?

Answer 22

• deeper soils are less likely to become waterlogged or to dry out rapidly
• can aid good root anchorage