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

What i s soil?

Bi ologi cal Soil Physi cal M i n eral (nutri ents) (structure)

Bi ology • Soil is a living environm ent • A handful of soil contains billions of organism 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

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

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 Turn over Am oun t Am oun t Fraction tim e (t/ ha) (%) (years) Microbial biom ass 0.3 (<1%) 2.4 Readily decom posed plant 0.1 (<1%) 0.2 m aterial (crop residues, livestock m anure) 0.6 (2%) 3.3 Resistant plant m aterial Physically protected organic 13.6 (47%) 71 m atter Chem ically stabilized organic 14.6 (50%) 2,900 m atter (hum us) 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

Opti m um pH • 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

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 CaCO 3

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 off each year som e phosphate and potash • Target bulky organic m anures to silage fields

Nutri ent values Man ure type Application Available Total Total rate N* N* P 2 O 5 K 2 O (kg / ha) (kg / ha) (kg / ha) 15:15:20 600 kg/ha 90 90 120 Cattle FYM 20 t /ha 24 64 160 30 m 3 /ha Cattle slurry 36 36 96 Values: *N availability will depend • 15:15:20 £165 /ha on application tim ing and • Cattle FYM £xxx /ha m ethod of incorporation • Cattle slurry £XXX/ha

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 NO x ) 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 250 200 150 100 50 0 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