Agritechnica 2016 Soil Compaction in Grassland. John Maher Teagasc, Ireland

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Giles Lawrence
5 years ago
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1 Agritechnica 2016 Soil Compaction in Grassland John Maher Teagasc, Ireland

3 600 mm 3000 mm 1300 mm

4 Monthly Rainfall (mm) in Ireland Grazing Conservation

5 Why Grazed Grass??? 285 Days of Feed Cost of feed (Energy Basis) 33% Cost of Grass Silage 25% Cost of Concentrate Grazed Grass: High Feed Value Provided it is managed well Cows Feed themselves Avoids harvesting cost Avoids storage cost & Feeding out cost Cows Spread their own Slurry

9 Soil Type Compact Easily Sand 6% Silt 53% Clay 41% Less Compaction Sand: 46% Silt: 46% Clay 8%

10 Compaction Causes Animal Traffic Machinery Traffic

11 Soil Structure + Compaction Structure Arrangement of soil particles and pore spaces between them Critical to all soil functions Compaction Alteration of the soil structure by compressive forces

13 Threats to structure Increased machine weight Increased intensity of operations Extended grazing season

14 Directly impedes root growth Compaction effects Influences access to nutrients and water Reduces soil pore space (50% - 30%) Less aeration for biological function (impacts on nutrient cycling: Denitrification) Less inflitration / drainage: Further root growth restriction Reduced uptake of nutrients (water) Reduced plant growth

15 Practical Impacts Reduced yield (grass or crop). Inefficient use of nutrients Ponding/Water on surface Weed grasses etc. Delayed field operations Machine Grazing

16 Compaction + Yield Teagasc Research: Yield Reductions Cereals 0 to 20% Maize 0 to 50% Grass 8 to 30%

17 Compaction Risk Factors Soil type (including OM) Presence or absence of vegetation Soil Moisture Content Machine weight, Ground pressure Traffic density Animal weight + Traffic density

18 Depth + Duration Shallow (< mm) Frequent in arable cultivation resolves? Frequency in Grassland Deep (>200mm) More difficult to resolve in all soils Persistence of compaction Typically 2 to 7 years Can be longer

19 Compacted Top-Soil Compacted Sub-Soil

20 Soil Examination (Visual) Spade extract 300mm undisturbed profile Examine for: Blocky, platy structure vs Crumb structure Horizontal layering vs vertical channels, Pans Earthworms Grey mottling Deep invasive roots

21 Examine Profile 300mm Spade-full

22 Preventing Compaction

23 Land Drainage (Deep Drains 1.8m)

24 Land Drainage (Shallow Drains 0.8m)

25 How do we Prevent? Restrict Traffic Animals: Grazing management Field Infrastructure Housing (get animals off when necessary) Breeding for Smaller Cows Machinery: Avoid in wet conditions Reduced loads and Pressures Larger tyres/lower Pressure

26 GRAZING TECHNIQUES: Grazing from Back Cow Walk Spokes of Wheel Strip-grazing Day 2 pm Day 2 am Day 1 pm Day 1 pm Day 2 am Morning Evening Tomorrow Evening Day 1 am Day 1 am Tomorrow Morning Roadway Farmyard Entry EXIT

29 Weight 4t 4t 8t Tyres Contact Area Air in tyre supports load Inflation pressure = Ground pressure Large tyres - big volume - low pressure 2.0 bar GP 1.0 bar GP 2.0 bar GP

30 1.0 bar GP 1.0 bar GP 2t 4t Axle load is important Soil Level 0.5m 100kpa 75kpa 50kpa 25kpa 1.0m

31 Fixing Compaction

32 Option 1: Time Allow soils to self repair Shrinking + swelling can help Frosts? (shallow) Must remove compaction cause (if obvious) Inexpensive and avoids doing harm May not be adequate!

33 Grassland - Aeration Shallow loosening ( mm) Spiker Teagasc Research 10 trial sites 3 years, multiple harvests. Some Initial responses (maybe N Mineralisation) No response to routine treatment

36 Subsoiling / Deep Loosening Loosens by shattering to greater depth mm Power demanding (45 kw / leg at 400mm) Leg spacing depends on depth and wings With wings = 2 x depth E.g. At 300mm depth: 600mm spacing: 5 legs in 3m Grassland Not suitable for rock / stone

40 Deep Loosening Effective? Prevention is better than cure Avoid the need for deep loosening Research not clear-cut Some Negative results Some Slightly positive results Little Longterm Benefit Arable research Re-compaction risk is real

41 Re-compaction risk Loosened soils Loose to depth of subsoiler More moisture through profile Prone to Re- Compaction May compact to deeper depth Shifting problem down even more difficult to solve

42 Soil Compaction Prevention is Better than Cure!!!

44 Prevention is better than Cure

27/01/2017. This event is being run by SAC Consulting. What is Soil?

27/01/2017. This event is being run by SAC Consulting. What is Soil? This event is being run by SAC Consulting What is Soil? 1 Soil Texture It describes the physical composition of the soil % of sand, silt and clay Refers to the mineral fragments of the soil only water