soil? Bi ologi cal Soil Physi cal M i n eral (nutri ents) - - PowerPoint PPT Presentation

What i s soil?

Soil

Bi ologi cal M i n eral

(nutri ents)

Physi cal

(structure)

Bi ology

• Soil is a living environm ent
• A handful of soil contains billions of
• rganism s
• They need air to breathe
• Essential for soils to function
• Com plex web of soil ecology that

turns dead plant and anim al m aterial into plant available nutrients, and m ix up the m ineral with the organic

M ites Earthworm s Nem atodes Bacteri a Collem bola Fungi Acti n omycetes

Earthw orm s

• Healthy soil indicator
• Soil drainage
• Casts are a good

source of available nutrients

• Can survive in

subm erged soils for 120 days

• pH >5.5

Tardi grades

Tardi grades

• Can survive extrem es:
• Tem perature

– Just above absolute zero to >100°C

• Pressure

– 6x greater than in the deepest ocean trenches

• Ionizing radiation

– 100s x higher than a lethal hum an dose

• Vacuum of outer

– go without food or water for >10 years!

Organ i c m atter

• Soil organic

m atter is a m ix of stuff that is:

– Alive – Dead – Very dead

Soil organ i c pools

Fraction Am oun t (t/ ha) Am oun t (%) Turn over tim e (years) Microbial biom ass

0.3 (<1%) 2.4

Readily decom posed plant m aterial (crop residues, livestock m anure)

0.1 (<1%) 0.2

Resistant plant m aterial

0.6 (2%) 3.3

Physically protected organic m atter

13.6 (47%) 71

Chem ically stabilized organic m atter (hum us)

14.6 (50%) 2,900

Jen ki n son (1981)

Organ i c m atter

• A good indicator of quality soils
• Very im portant!

– Fuels biological activity – Drainage – Structural stability – Water holding capacity – Drought resistance

Soil organ i c m atter

• Can be lost by

– Erosion –

• Can be preserved with

– Ley periods – Bulky organic m anure application – Deep rooting crops – Good nutrient budgeting – Reducing tillage

Soil organ i c m atter

• Soil texture can indicate organic

m atter levels

• Sandy soils can be down to ~2%
• Organic/peat soils are >20%
• Influences heavy m etal toxicity and

trace elem ent availability

– So affects target pH

Soil pH

• The pow er of Hydrogen (H +)
• A m easure of acidity or alkalinity
• Very im portant, because it affects:

– Nutrient availability – Biology – Even has an effect on soil structure (Ca:Mg ratio)

• nutrient deficiencies

Soil pH

• Influences plant growth
• Nutrient availability

– Particularly phosphate

• Trace elem ents / potentially toxic ions

– Essential m anganese (Mn) is deficient at a higher pH – Toxic alum inium (Al) is available at a lower pH

Target pH for soils

• Depends on soil type and croppin g
• Mineral soils

– Target pH 6.2 (rotational ground) – Target pH 5.9 (perm anent grass)

• Peaty soils

– Target pH 5.1 (perm anent grass)

• Based on old fashioned W sam pling

Soil texture

• pH will drop at

different rates in different soils

– Managem ent – Soil texture

• Sandy soils little

and often

• Clay soils less

frequently

W sam pli n g

• Maintaining optim um pH in the

topsoil is im portant for

– Optim um yields – Consistent crop quality – Good root developm ent

• Maxim ise nutrient uptake
• Minim ise nutrient losses

– To air and water

Opti m um pH

Soil an alysi s

• Every 4 or 5 years; keep an eye on:

– pH – Phosphate (P) – Potash (K) – Magnesium (Mg)

• Lim e little and often
• Aim for Moderate P and K status
• Replace what you take off

– Silage takes off m ore than grazing

Soil sam pli n g

• Get your soils sam pled an d an alysed!
• Soil sam pling

– Take lots of subsam ples – W form ation – 15 cm deep – Bulk them together

Soil an alysi s

• Can test for other things:

– Sulphur (S) – Cobalt (Co) – Copper (Cu) – Organic m atter (LOI)

• the soil has been lim ed

– Lim e is CaCO3

Nutri ent m an agem ent

• Replace what you take off

– Silage takes off m ore than grazing, and can rem ove lots of potash that needs replaced – Grazed perm anent grass takes very little

• ff each year som e phosphate and

potash

• Target bulky organic m anures to

silage fields

Nutri ent values

Man ure type Application rate Available N* N* (kg / ha) Total P2O5 (kg / ha) Total K2O (kg / ha)

15:15:20 600 kg/ha 90 90 120 Cattle FYM 20 t /ha 24 64 160 Cattle slurry 30 m 3 /ha 36 36 96 Values:

• 15:15:20

£165 /ha

• Cattle FYM

£xxx /ha

• Cattle slurry

£XXX/ha *N availability will depend

• n application tim ing and

m ethod of incorporation

Organ i c m anures N

• 1. Readily available nitrogen

– Im m ediate uptake, am ounts vary with application tim ing and incorporation

• 2. Crop available N

– For the following crop

• 3. Potentially available N

– Broken down slowly, available over several years – Bulky organic m anures, i.e. m uck

Nutri ents P & K

• Get your soils sam pled an d an alysed!
• Target organic m anures (i.e. m uck) to

fields with low K and/or P status

• Take organic m anures into account,

especially if you always apply to the sam e fields

Nutri ents N

• Muck will also provide som e N, and

sm all but significant quantities of trace elem ents

• Take clover into account

– Craibstone cam pus) the average rate of N fixation was 112 kg N /ha /year (~90 units /acre) – This could be higher on the west coast (m ilder and wetter clim ate)

DI Y soil assessm ents

• How easy is it to dig?

– Soil structure

• Earthworm s

– Num ber – Diversity

• Sm ell
• Colour
• Wetness
• Root growth

Soil structure

• Com paction of the upper soil layers:

– Lim its root developm ent – Restricts nutrient uptake – Reduces growth potential – Reduces yield

• Com paction is associated with

denitrification (loss of NOx) a particularly bad GHG

Poor structure: causes

• Livestock

– Overgrazing – Poaching

• Heavy m achinery

– Over-cultivation – Working in wet conditions

Prabost average m onthly rai n fall (m m ), 1981 2010

50 100 150 200 250

Prabost Edin burgh

Aerators & subsoilers

• Soils need air to

breathe

• Soil life

– Nitrogen fixation – Nutrient cycling

• Drainage
• Rooting

Topsoil tri al: results

Sw ard li fter Aerator No treatm ent

Roots

• Deep roots can open up

the soil

– Red clover – Chicory – Cocksfoot – Mustard

• Also

– Provide organic m atter – Bring up trace elem ents

Messages

• Keep an eye on your soil
• Carry out soil sam pling and analysis
• Keep the soil in the right pH range
• Replace the nutrients you take off
• Check your soil structure