Pugging ruins soil structure

The worst possible thing you can do to your pastures when the ground is saturated is to allow stock to pug them. This is a major concern during winter in most parts of New Zealand with its light volcanic soils and heavy rainfall.

In the past, although farmers never liked pugging their paddocks, they always believed that in a few days when a green tinge appeared, that all would be well, and pastures would be back to full production in a few weeks. But recent research has shown that pastures and soils do not recover quickly.

Pugging pastures damages the delicate crumb structure of the soil which carries the air in the soil, and it could take up to nine months before this is restored and production back to normal. Indeed in some cases, where pastures have been turned into brown porridge, researchers cannot say how long that damage will take to repair – if it ever does.

Every hectare of a farm is precious, and farmers need to take special care and know what to do to avoid pugging damage in wet spells in winter. It's important to have an area where stock can be held off pasture during very wet spells, and to know when they should be removed.

Limiting soil and pasture damage in winter

Background

• When the soil surface cannot support hooves of grazing animals, especially when wet, small depressions occur which then hold more water.
• Walking on this surface compounds the problem and mud results.
• The delicate crumb structure of the soil is lost as they become waterlogged.
• The roots and growing points of plants are damaged.
• Pasture production can be reduced by as much as 80% for up to 8 months.

Avoiding problems

• Have a good pasture cover for calving by building up pasture before calving.
• Graze wetter paddocks before the wetter part of the season.
• Use a slow rotation – greater than 80 days in winter. When its dry go slower.
• Shift stock before daybreak to minimise activity. Hungry stock waiting for their new break walk up and down the fence and pug the pasture.
• Make breaks as square as possible, to prevent stock walking up and down a long fence face.
• Stay away from stock when very wet to avoid disturbance, encouraging the to walk about.
• Start grazing from the back of the paddock to the front. So when you move them they walk over long pasture to prevent damage.
• Minimise supplements fed out in the paddock. This reduces vehicle damage and reduces stock concentration.
• Use a stand-off area.
• Use a farm bike rather than a tractor.
• Use a back fence to prevent further damage.
• Use on-off grazing, having stock on pasture for as low as 4 hours before holding them off.

Soil and Fertiliser Glossary

Acidulated: Fertiliser manufacturing process where acids are used.
Aeration: Process where air gets into the soil pores.
Aggregate: Cluster of soil particles (sand, silt and clay).
Allophanic soils: Soils containing aluminium and silicon formed from volcanic ash.
Alluvial soils: Soils deposited on land by water.
Ammonium nitrate: Inorganic fertiliser with 33% or rapidly available N.
Ammonium phosphates: Inorganic fertiliser containing N(33%).
Ammonium sulphate: Inorganic fertiliser containing N(21%) and S(24%).
Ammonium nitrogen: Inorganic soluble form of N.
Anion: Ion carrying one or more negative charges.
Anion storage capacity (ASC): Measure of the capacity of soil to store nutrients e.g. P and S: Previously known as phosphate retention capacity.
Ash soils: Yellow-brown loams, brown granular loams and clays, and red brown loams, derived from volcanic eruption.
Available nutrients: Nutrients in soil easily absorbed by plants.
Available water: Proportion water in soil that is easily absorbed by plants.
Available water-holding capacity: Sum of available water capacity of each root-containing layer.
Bare fallowing: Fallow leaving bare soil.
Base saturation: Percentage of cation exchange capacity of a soil saturated with basic cations.
Base cations: Calcium (Ca), magnesium (Mg), sodium (Na) and potassium (K).
Biomass: Living organisms in the soil.
Borax: Trace element fertiliser containing 11% boron.
Boron: B.
Border dyking: Levees or borders to control flow of water on to land.
Brassica crops: Cauliflowers, cabbages, turnips and Swedes.
Brown earths: Aerobic soils with brown colour due to iron particles on soil particles.
Buffering capacity: Ability to resist changes in pH; also changes in concentration in nutrient concentration.
Bulk density: The mass of a standard volume of soil.
C:N ratio: Concentration of carbon in organic matter divided by the concentration of nitrogen.
Calcareous: Containing calcium carbonate (limestone).
Calcined magnesite: Inorganic fertiliser containing 50-55% magnesium in rapidly available form.
Calcium sulphate: Gypsum. Inorganic fertiliser containing S(20%) in rapidly available form.
Cation: Ion carrying one or more positive charges.
Cation storage capacity (CSC): Measure of capacity of a soil to store nutrients e.g. Ca, M.G., K and Na. Also called cation exchange capacity.
Chelates: Trace elements combined into organic molecules which makes them readily available to plants.
Clay soils: Soil containing fine mineral particles no bigger than 0.002mm in diameter.
Clod: Large dense lump of soil.
Co: Cobalt.
Coarse soil texture: Soil dominated by sand-sized mineral particles.
Cobalt sulphate: Trace element fertiliser containing Co (21%).
Compaction: Soil where heavy machinery of stock have destroyed air-filled pores.
Concretion: Soil particle composed mainly of a single chemical compound e.g. Calcium carbonate or iron oxides.
Copper sulphate: Trace element fertiliser containing Cu(25%).
Cover crop: Crop planted to protect the soil surface or seed planted after it has started to grow e.g. Grass seed in crop of barley.
Crop residue: Unharvested part of a crop (roots and straw).
Crop rotation: Sequence of different crops grown on an area of lad which could include a fallow.
Crumb structure: Small, rounded, porous aggregates in soil.
Denitrification: Reduction of nitrate or nitrate nitrogen to gaseous form.
Development fertiliser: Fertiliser applied to boost the overall fertility of a farm.
Diammonium phosphate: Inorganic fertiliser containing N (18%). P (21%) and K(0), S(2%).
Dolomite: Form of limestone containing calcium or magnesium carbonate. Has 10% Mg in slow release form.
Effective root depth: Depth of soil before root penetration stops.
Elemental Sulphur: Inorganic fertiliser which is 100% S in slow release form.
Equivalent acidity: Weight of pure calcium carbonate (limestone) to neutralise the acidity caused by applying 100kg of fertiliser.
Erosion: Loss of soil by wind, water or ice.
Essential plant nutrients: Chemical elements essential for normal plant growth.
Eutrofication: Enrichment of surface water with plant nutrients causing weed and algal growth, and anaerobic conditions.
Fallow: Period when no crop is grown.
Fe: Iron.
Ferrous sulphate: Trace element fertiliser containing 19% Fe.
Fertiliser: Any organic or mineral material added to soil to supply essential nutrients for plant growth. (Not the legal definition).
Field capacity: Soil water content 2-3 days after a saturated soil has been allowed to drain, and when free drainage has stopped.
Fine texture soils: Soils in which fine particles (clay and silt) predominate.
Fixation: Process that converts plant nutrients from soluble form to less soluble form.
Friable soil: Soil which breaks down with ease to desirable tilth.
Gley soil: Soil developed under poor drainage.
Granular structure: Soil with well-defined crumb structure.
Green manuring: Growing a crop e.g. oats, lupins to plough back into the soil.
Ground water: Zone below soil surface in which water can move freely.
Growing degree days: Number of days when air temperature is above 10ºC.
Gumland soils: Soils containing the resin from kauri trees.
Gypsum: Inorganic fertiliser containing 20% S in rapidly available form. Calcium sulphate.
Heavy metal: Toxic metallic elements e.g. Cadmium, mercury, arsenic, chromium, lead and nickel.
Horizon: Horizontal layers in the soil profile differing in appearance and chemical properties.
Hump and hollow: Reshaped land surface to help drain off surface water.
Humus: Stable form of organic matter in soil containing plant and animal residues decomposed by micro-organisms.
Impeded drainage: Condition where no free movement of water through soil is possible.
Impervious: Resistant to water or plant roots.
Infiltration: Entry of water into the soil surface.
Immobilisation: Reverse of mineralisation.
Inorganic: Mineral substances containing carbon only in the form of carbonates.
Intrazonal soils: Soils influenced when formed by parent material or temporary or permanent saturation.
Ions: Electrically charged particles formed when substances dissolve in water. Anions have negative charge and cations have positive charge.
Iron pan: Narrow layer of soil in which individual particles are cemented together by iron oxides.
Labile nutrients: Plant nutrients in soil that are able to replenish the soil solution rapidly to maintain plant growth.
Land classification: Grouping land into categories based on suitability for purpose.
Leaching: Removal of nutrients from upper soil layers by downward movement of water.
Limestone: Rock made up mainly of calcium carbonate.
Liquid fertilisers: Fertilisers spread in liquid form.
Loam: Soil containing sand, silt and clay-sized particles without any one type dominating.
Macronutrient: Element required in large amounts for plant growth.
Magnesium oxide: See Calcined magnesite.
Magnesium sulphate: Inorganic fertiliser containing 10% Mg in rapidly available form.
Maintenance fertiliser: Fertiliser applied to replace nutrients removed from the soil.
Manganese sulphate: Trace element fertiliser containing 24% Mn.
MAX: Maximum available water-holding capacity of soil root zone.
Mb: Molybdenum.
Melanic soils: Soils with dark surface horizon rich in nutrients such as Ca and Mg.
Micronutrient: Element required in small amounts (ppm) for plant growth.
Mineral nitrogen: Soluble N compounds in nitrate, nitrite or ammonium forms.
Mineral soil: Soil consisting mainly of mineral materials and less than 20% organic matter.
Mineralisation: Process where micro-organisms convert plant nutrients from organic to inorganic form.
Mn: Manganese.
Mole drainage: Dragging metal plug (mole) through soil to make drainage tunnels.
Monoammonium phosphate: Inorganic fertiliser containing N(11%). P(21%) and K(0), S(2%).
Mulch: Material applied to soil to prevent water loss by evaporation and suppress weed growth.
Nitrate nitrogen: Inorganic soluble form of N.
Nitrogen assimilation: Incorporation of N into organic materials by living organisms.
Nitrogen cycle: Process of how nitrogen is used in a grazing system incorporating N from the air, the role of N fixing by legumes, and return of dung and urine from the animal.
Nitrogen fixation: Conversion of nitrogen gas in the air by rhizobia bacteria on roots of legumes into forms that can be used by plants.
Nutrient budget: Exercise to balance nutrients applied with nutrients removed from the farm.
Nutrient cycling: Process of nutrients moving from soil to plants and returned again to soil.
Olsen P test: Measure of plant available P.
Organic soil: Soil containing more than 20% organic matter.
Over liming: Applying more lime than needed to achieve optimum pH.
Oxidation pond slurry: Content of farm oxidation pond used as organic fertiliser.
Parent material: Material from which the soil is formed.
Partially acidulated phosphate rock (PAPR): Inorganic fertiliser containing P in both soluble and slow release form. Total P content around 15%.
Peat: Soil formed by accumulation of undecomposed or partially decomposed plant residues.
Permanent wilting point: Water content of soil at which plants wilt and don’t recover.
Permeability: Ease which with water, gases or water can pass through a soil.
pH: Measure of acidity or alkalinity of soil.
Phosphate retention capacity: Soils capacity to absorb phosphate anions.
Plasticity: Ability for soil to stay in shape after being moulding with fingers.
Plough pan: Soil layer with poor permeability formed below depth of regular cultivation.
Poaching: Same as pugging.
Podzols: Strongly leached acid soils with clearly defined bleached horizon.
Porosity: Volume of pores as percentage of volume of soil.
Potassium chloride: Inorganic fertiliser containing 50% potassium in rapidly available form.
Potassium sulphate: Inorganic fertiliser containing 40% K and 17% S in rapidly available form.
Profile: Vertical section through soil exposing different horizons.
Pugging: Destruction of surface structure of wet soils by stock or traffic.
Pumice soils: Soils formed from volcanic pumice.
Quick test K(QTK): Measure of plant available K.
Quick test Mg(QTMG): Measure of plant available Mg.
Raw soils: Very young soils with no distinct profile.
Reaction: Acidity or alkalinity of soil expressed as pH value.
Reactive phosphate rock (RPR): Natural occurring, slow-release P fertiliser containing between 12-15% P. An unacidulated fertiliser.
Recent soils: Weakly weathered soils with little profile but with distinct topsoil.
Rhizobia: Bacteria live in root nodules on legumes that convert atmospheric N into plant available N.
Rhyolite: Derived from rhyolite, a fine-grained igneous rock that occurs in larva flows.
Rill erosion: Erosion forming small gullies or rills on soil surface.
Ripping: Same as subsoiling.
Root nodules: Small growth on roots of legumes containing rhizobia bacteria.
Root zone: Depth to which roots penetrate.
Run-off: Rainfall or irrigation water which flows off soil surface.
Saline soils: Salt-affected soils.
Sand: Mineral soil particles between 0.02 and 2mm in diameter.
Sandy soil: Soil with texture dominated by sand fraction.
Saturate: To fill to capacity e.g. Soil pores with water.
Se: Selenium.
Sedimentary soil: Soil formed by layers of material deposited by wind or water.
Sheet erosion: Small amounts of soil eroded in a uniform manner from soil surface.
Silt: Mineral soil particles between 0.002 and 0.02mm.
Silting: Deposition of water-borne soil particles in a stream or lake or on flooded land.
Sulphur leaching index (SLI): Index of likely loss of sulphate Sulphur from root zone by leaching.
Slow-release fertiliser: Fertilisers that release their nutrients over an extended period.
Sodium molybdate: Trace element fertiliser containing 39% Mb.
Sodium selenate prills: Trace element fertiliser containing 1% Se.
Soil cap: Dense layer on surface of soil.
Soil solution: Water in soil and materials dissolved in it.
Soil structure: Arrangement of primary soil particles (sand, silt, clay) into aggregates.
Soil tests: Chemical estimates of soil‘s ability to supply nutrients available to plants.
Soil water deficit: Difference between actual amount of water in soil and its water holding capacity.
Solubor: Trace element fertiliser containing 20% Bo.
Sorption: Combination of adsorption and absorption where ions are removed from soil solution by reacting with soil particles.
Subsoil: Soil below B horizon, below cultivated layer or below the root zone.
Subsoiling: Breaking the compact subsoil with tines and without inverting it.
Subsurface tillage: Cultivation with blade to cut plant roots to loosen soil without inverting it.
Sulphate of ammonia: See ammonium sulphate.
Sulphate Sulphur: Inorganic soluble form of S.
Sulphur leaching index: Empirical assessment of potential for sulphate Sulphur to be leached from soil.
Superphosphate(Single super): Rapid release inorganic fertiliser containing around 9%P and 12% S. A fully acidulated P fertiliser.
Superphosphate(Triple super): Rapid release inorganic fertiliser containing around 20%P and 2% S. A fully acidulated P fertiliser.
Surface drains: Reshaped land surface to help removal of surface water.
Texture: Relative proportion of solid primary particles (sand, silt and clay) in a soil.
Tile drain: Clay pipes in subsoil to remove surface water.
Tilth: Fine texture of topsoil required before sowing.
Topsoil: Uppermost layer of soil. The cultivated area.
Ultic soils: Strongly weathered soils with accumulation of clay in the subsoil.
Unacidulated: Process in fertiliser manufacture involving acid.
Urea: Inorganic fertiliser with N (46%) in rapidly available form.
Whey: Byproduct from cheese manufacture used as cow feed or fertiliser.
Virgin soil: Uncultivated soil.
Volcanic rock: Rock derived from volcanic activity e.g. Basalt, pumice and rhyolite.
Volumetric water content: Volume of water in soil as percentage of soil volume.
Water stress: Stress in plants caused by inadequate water.
Water table: Level below which a soil is saturated with water.
Weathering: Physical and chemical changes caused by atmospheric forces occurring near the surface.
Wilting point: Same as permanent wilting point.
Wind erosion: Caused by particles blown by wind.
Zinc sulphate: Trace element fertiliser containing 23% Zn.
Zn: Zinc.
Zonal soils: Soils in which climate and vegetation are the most important soil-forming factors.

Information source: I.S. Cornforth (1998). Practical soil management. Lincoln University Press. ISBN 0-909049-15-7