The Role of the Soil Biological Community in Improving the Health of Agricultural Soils

The Role of Soil Biology in Agriculture

Importance of Agricultural Land

• Only 7.5% of the Earth's surface is suitable for agriculture.

• The remainder is covered by ice, water, stone, deserts, or cities.

• Agricultural land is undervalued, leading to degradation.

  • About 40% of the world’s agricultural land is no longer fertile and has been abandoned

  • 40-50% of the current agricultural land is seriously degraded

• Soil loss occurs at an alarming rate:

  • A soccer pitch of soil is lost every five seconds due to erosion or desertification.

  • If current practices continue, only about 60 years of topsoil remain.

Soil Erosion: Australian and Global Perspectives

Australia

• Losing 2.2 tonnes of soil from water erosion per hectare per year.

  • Equivalent to almost 1 mm of topsoil annually, while it takes 100 years to build 1 mm of topsoil.

• Soil loss is happening 100 times faster than soil formation.

  • Approximately half of Australia's topsoil has disappeared since European settlement.

• Evidence of soil erosion visible in New Zealand glaciers stained by red and black dust from Australia.

Globally

• Since humans began farming, soil erosion has claimed an area larger than the USA and Canada combined.

Soil Contamination

China

• Feeds 20% of the world’s population with less than 10% of the world’s arable land.

• 81% of China’s coastline is heavily polluted with nitrogen, phosphate, fluoride, and oil.

• Significant soil contamination:

  • One in five hectares is poisoned by substances like cadmium, nickel, and arsenic.

  • An additional 3.32 million hectares are moderately polluted.

New Zealand

• Cadmium from phosphate fertilizer poses issues on dairy farms.

• Two-thirds of all rivers are un-swimmable due to nitrogen runoff from dairy farms.

• Copper, used as a fungicide, has accumulated in vineyards.

Europe

• 137,000 square km of agricultural land requires remediation due to cadmium, chromium, copper, mercury, lead, zinc, antimony, cobalt, and nickel.

USA

• Annual application of 12 million tons of nitrogen and 4 million tons of phosphorus fertilizer.

  • Half ends up in waterways.

• Annual application of half a million tons of pesticide.

  • At least one pesticide found in 94% of water samples and 90% of fish samples from streams.

Salt Contamination

• Deforestation leads to rising water tables, bringing salt to the surface.

• Western Australia has massive saltpans, with 1 million hectares of agricultural land lost to salt.

Nitrogen Fertilizer and the Green Revolution

• Nitrogen fertilizer decreases microbial activity.

• Only 30-40% of the nitrogen applied is used by the plant.

• Excessive fertilizer use leads to water pollution and dead zones in coastal oceans.

• Nitrous oxide, a potent greenhouse gas, is emitted.

• The Green Revolution increased food supply but resulted in a simpler, less stable soil ecosystem that no longer teems with life.

Lecture Objectives

• Become familiar with soil organisms and their ecosystem services.

• Understand how they sustain soil health.

• Learn about the impact of agricultural management practices on soil health.

• Identify practices to improve soil health.

Soil as a Complex Ecosystem

• Soil is the most complex and biologically diverse ecosystem on Earth.

• A teaspoon of healthy agricultural soil contains:

  • Many billions of bacterial cells

  • Kilometers of fungal hyphae

  • Thousands of protozoa

  • Hundreds of nematodes

  • Numerous insects, mites, and small animals

• Globally, there are likely to be over a million species of fungi and a million species of nematodes.

• This is compared to only 9000 bird species.

The Soil Food Web

• A community of organisms in soil interacting with each other.

• It is a competitive environment where each organism fights for food and habitat.

Soil Organisms

Bacteria

• Single-celled prokaryotic microbes.

• Often the most abundant microbes in soils, with many millions of species.

• Usually > 10^{10} bacteria/g soil.

• Metabolically versatile, feeding on non-living soil organic matter.

• Some form symbiotic relationships with plants and play a role in plant nutrition.

• Decompose pesticides and other pollutants.

Bacteria in the Wheat Rhizosphere

• A DNA study detected 9885 unique sequences, primarily bacteria.

• 27 bacterial groups were identified, with some containing more than 300 genera.

• Dominant groups: Proteobacteria (blue), Actinobacteria (red), Firmicutes (green).

Actinobacteria

• Aerobic, spore-forming gram-positive bacteria.

• Play a significant role in improving soil health.

  • Decompose organic materials like lignin, cellulose, and chitin.

  • Improve nutrient availability.

  • Inhibit the growth of plant pathogens.

Soil Fungi

• Important for the degradation of recalcitrant substances like lignin and cellulose.

• Lignin is degraded by saprophytic fungi.

• Cellulose is degraded by fungi producing a battery of enzymes.

• In some environments, there may be 250 kg of dry fungal hyphae/ha in the upper 5 cm of soil, equivalent to 3 km of hyphae/g soil.

• Without fungi, the world would be covered in organic debris.

Protozoa

• Reside in water-filled pores and move in water films.

• Numbers may be as high as 10^9 - 10^{10} /m^2.

• Three major groups: flagellates, amoebae, and ciliates.

• Feed on bacteria, fungi, or are omnivorous.

Nematodes

• The most numerous multi-cellular animals on earth (in terms of numbers of individuals).

• Healthy soils have at least 10 million nematodes/m^2.

• Some are plant parasites, but most are beneficial, feeding on bacteria, fungi, and other soil organisms.

Soil Microarthropods

• Two main groups: mites (Acari) and springtails (Collembola).

• Generally range in size from 0.2 mm to about 1 mm, but springtails may be 3 mm long.

• Live in soil pore spaces.

• Feed on decomposing plant detritus, fungi, nematodes, and other small arthropods.

• Key roles:

  • Mineralize nutrients.

  • Regulate populations of the soil fauna.

Other Mesofauna

• Enchytraeids (potworms):

  • Resemble earthworms but much smaller.

  • Ingest organic matter and associated microorganisms.

• Symphylans:

  • Centipede-like animals.

  • Generally omnivorous but can feed on plant roots.

• Tardigrades (water bears):

  • Amongst the most resilient animals known.

  • Survive extreme temperatures, pressures, air deprivation, radiation, dehydration, and starvation.

Macrofauna

• A wide array of taxonomic groups in many trophic levels.

  • Isopods and millipedes are major consumers of organic debris.

  • Insect larvae, such as cane grubs, consume root material.

  • Centipedes, spiders, scorpions, and beetles are the dominant predators in soil and litter.

Ants and Termites

• Ants:

  • Insects that live in colonies.

  • May comprise 15-25% of terrestrial animal biomass.

  • Generalist predators and scavengers.

  • Tunnels increase air and water flow in soil.

• Termites:

  • ‘Keystone species’ in the tropics and subtropics.

  • Most feed on decaying organic matter.

  • Some use flagellate protozoa in their gut to degrade cellulose.

  • In some species, gut bacteria fix atmospheric nitrogen.

• Ants and termites increased water infiltration, improved soil nitrogen, and increased wheat yields by 36% in a Western Australia study.

• These ecosystem engineers undertake the role of earthworms in hot, dry habitats.

Earthworms

• Play a key role in soil formation, organic litter decomposition, and the redistribution of organic matter in soil.

• Three ecological groups:

  • Epigeic species: Reside on the soil surface, don’t build burrows or produce casts.

  • Anecic species: Form deep burrows, incorporate large amounts of organic matter into soil.

  • Endogeic species: Only form burrows in upper soil layers; faecal pellets provide a favourable environment for microbial growth.

• Charles Darwin: “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures”.

Soil Food Web Diagram

• Illustrates the relationships between different trophic levels:

  • Plants (Photosynthesizers)

  • Organic matter (Waste, residue and metabolites)

  • Bacteria and Fungi (Decomposers/Mutualists, Pathogens/Parasites, Root-feeders/Grazers)

  • Arthropods, Nematodes and Protozoa (Shredders, Fungal- and Bacterial-feeders, Predators)

  • Birds and Animals (Higher Level Predators)

Ecosystem Services Provided by Soil Biota

• Provide a soil environment suitable for plants.

• Improve aggregation, create pore spaces, increase water infiltration, improve drainage.

• Fungal hyphae promote aggregation by producing binding agents.

• Earthworms produce macropores and fungal hyphae bind soil together.

Earthworms and Soil Fertility

• Earthworm casts are nutrient-rich with more N, P, and K than surrounding soil.

• Earthworms convert organic matter into humus and move it down the soil profile.

• Healthy soils usually have more than 250 earthworms/m^2.

Nitrogen Fixation by Bacteria

• Rhizobium bacteria enter root tissue and modify host cells to form nodules.

• Bacteria in these nodules convert nitrogen gas from the atmosphere to ammonium.

• The amount of N produced depends on legume species and growing conditions but is usually 100-200 kg N/ha/year.

Nutrient Mineralization by Soil Organisms

• Nematodes (and other soil organisms) feed on fungi and bacteria and release nutrients from microbial cells.

• Organic matter is decomposed by bacteria and fungi.

• Nutrients are released in mineral form (e.g., ammonium in nematode faeces) and are used by plants.

Carbon to Nitrogen Ratio in Nutrient Cycling

• Predators have a higher C/N ratio than their prey, facilitating nutrient cycling.

• Example: Bacterial feeding nematode C/N = 6:1, Bacteria C/N= 4:1.

• Nematode obtains 12 C and 3 N from bacteria, but only needs 2 N. The excess N is excreted and used by plants.

Experimental Evidence for Nematode Impact on Plant Growth

• Classic experiment showed that adding microbial-feeding nematodes to soil enhanced N uptake and improved perennial grass growth.

Quantification of Nitrogen Mineralization by Nematodes

• Fungal and bacterial-feeding nematodes mineralize between 1 and 6 nanograms N/nematode/day.

• Assumptions:

  • 1400 t soil/ha

  • 5 nematodes/g soil

  • 4 ng N is mineralised/nematode/day

• Calculation: 10 kg N is mineralised by nematodes/year.

• In a healthier soil with 25 nematodes/g soil, 50 kg N would be mineralised.

• Free-living nematodes are significant contributors to the soil nitrogen pool.

Arbuscular Mycorrhizal Fungi (AMF)

• Branched hyphae (arbuscles) form within root cells for absorption.

Role of Mycorrhizal Fungi in Plant Nutrition

• Soils usually contain large amounts of P as Phosphates.

• Phosphates have low solubility, making it difficult for plants to acquire.

• Roots taking up orthophosphates (Pi) create depletion zones in the rhizosphere.

• Plants increase Pi uptake through AM symbiosis (used by ~80% of plant species).

• The fungus obtains carbon from the plant and provides the plant with nutrients (mainly phosphorus).

Mechanisms of Improved Phosphorus Uptake

• Hyphae have a smaller diameter than roots, allowing them to explore a greater soil volume.

• A well-developed hyphal network absorbs Pi several centimetres from the root surface.

• Pi is translocated rapidly to roots, overcoming slow diffusion in the soil solution.

Benefits of AM Fungi

• Improve drought tolerance by acting as an extension of the root system.

• Enhance disease resistance and tolerance by reducing plant stress from nutrient deficiencies or drought.

• Compete with pathogens for carbon within roots and labile carbon exudates outside roots.

• Hinder access of soilborne pathogens to root cells once occupied by mycorrhizal fungus.

AM Fungi and Soil Structure

• Improve soil structure through the production of glomalin, a binding agent.

Glomalin

• A glycoprotein containing 30-40% carbon.

• Produced only by arbuscular mycorrhizal fungi.

• Functions:

  • Sealant for hyphae, turning them into pipes for water and nutrient transport.

  • Provides rigidity to hyphae, allowing them to span air spaces between soil particles.

Glomalin and Aggregate Formation

• When hyphae stop transporting or die, glomalin sloughs off into the soil.

• Acts as a ‘super glue,’ binding organic matter to sand, silt, and clay particles, forming aggregates.

• Benefits of aggregation:

  • Reduced wind and water erosion.

  • Porous soil structure for water, air, and root movement.

  • Increased water-holding capacity.

  • Harbors beneficial microbes.

Agricultural Practices Disrupting AMF

• Frequent inputs of P fertilizer.

• Long fallow periods.

• Cultivation of non-host crops (e.g., Brassicaceae).

• Frequent tillage.

• Soil fumigation.

Differing Opinions on Non-Mycorrhizal Break Crops in Australia

• Brassicas as biofumigants (e.g. canola) reduce soilborne pathogens, including fungi, bacteria, and nematodes.

• Some argue disease control benefits outweigh benefits from AM fungi.

• Canola reduced Pratylenchus thornei populations on the Darling Downs.

• Wheat yields were lowest following canola due to poor colonisation by AM fungi; AM fungi provided benefits because the season was dry and soil P concentrations were low.

Ongoing Arguments Regarding AM Fungi

• Some argue there is no need to manage AM fungi due to their limited impact on crop nutrition and productivity.

• Others disagree, emphasizing benefits such as better P uptake and drought tolerance.

• Arbuscular mycorrhizal fungi provide many benefits to plants, including better P uptake and tolerance to drought.

• Dry environmental conditions and low P levels are common in Australia. Will the next generation of agricultural scientists continue to ignore AM fungi?

Plant Pathogens in Soil

• Bacteria, fungi, oomycetes, nematodes can be plant pathogens

• Examples: Root-knot nematode, Bacterial wilt, Pythium root rot, Sclerotium base rot

Soil Organisms and Disease Suppression

• Most soil organisms are beneficial and suppress diseases.

• A disease-suppressive soil has an active and diverse biological community.

• Organisms regulate pest and pathogen populations through predation, parasitism, competition, and production of antibiotics, toxins, or enzymes.

Nurturing Soil Biology

• Soil biology provides essential ecosystem services such as:

  • Decomposing plant residues into soil organic matter.

  • Improving soil structure, water infiltration, and drainage.

  • Providing plants with nutrients.

  • Fixing nitrogen from the atmosphere.

  • Mineralizing nutrients from organic matter.

  • Protecting plants from pests and pathogens.

  • Reducing soil erosion.

  • Minimizing nutrient losses.

  • Mitigating climate change by sequestering carbon.

  • Degrading pesticides and other pollutants.

Impact of Agricultural Management Practices on Soil Health

Soil Carbon

• A food source for microorganisms with beneficial roles.

• Allows water to infiltrate more rapidly and improves drainage.

• Increases water-holding capacity.

• Improves aggregate stability.

• Improves root growth by reducing bulk density.

• Improves cation exchange capacity.

• Improves plant nutrition through nutrient supply and cycling.

• Reduces damage from pests and pathogens due to competition from antagonists.

Impact of Agriculture on Soil Carbon

• Organic carbon levels in most agricultural soils have declined significantly.

• Most losses occurred when land was first farmed, but losses continue today.

• CO_2 losses contribute to greenhouse gas emissions from agriculture.

• Low levels of soil organic carbon affect the soil biology.

Example of Sugarcane's Detrimental Effects

• Comparison of sugarcane vs. pasture sites showed that sugarcane:

  • Reduced total organic C from 2.7% to 1.4%.

  • Reduced labile C from 0.24% to 0.11%.

  • Reduced microbial activity from 1.1 to 0.47 µg FDA/g/min.

  • Reduced cellulase activity from 27.0 to 4.5 µg PNP/g/day.

  • Reduced free-living nematodes from 3630 to 1288/200 mL soil.

  • Increased the percentage of plant-parasitic nematodes from 8% to 51% of the total nematodes.

Reasons for Soil Carbon Loss

• Tillage:

  • Exposes previously protected organic matter, accelerating decomposition and mineralization to CO_2.

• Wind and water erosion:

  • Annual losses of topsoil (with carbon and nutrient-rich fractions) can be as high as 8 t soil/ha.

• Periods of bare fallow:

  • Provide no carbon inputs and increase erosion risk.

• Loss of ground cover:

  • Burning crop residues or removing them for other uses.

• Replacement of pastures with continuous cropping:

  • Perennial pastures have a higher root:shoot ratio and deeper rooting habits than annual crops.

  • Less organic matter is removed when livestock is sold rather than plant produce.

Tactics to Increase Soil Organic Matter

• Minimize tillage.

• Grow healthy crops and pastures:

  • Grow more plant biomass.

  • Include cover crops in the rotation.

  • Use plants with deeper rooting habits.

  • Increase crop diversity (multi-species mixes).

  • Intercropping.

• Retain crop residues as mulch (i.e., stubble retention).

• Reduce periods of bare fallow.

• Apply animal manures, recycled organic wastes, and compost.

• Encourage earthworms and other ecosystem engineers.

• Multiple practices must be integrated into the farming system.

Negative Effects of Agricultural Management Practices

• Tillage is detrimental to many beneficial soil organisms.

Tillage Destroys Mycorrhizal Networks

• When soil is consistently cultivated, ecosystem services provided by mycorrhizae are lost:

  • Uptake of water and nutrients.

  • Disease resistance.

  • Drought tolerance.

Tillage is Detrimental to the Soil Fauna

• Larger soil organisms (e.g., microarthropods, omnivorous nematodes, and macrofauna) are more affected by tillage than smaller ones.

• Many of these animals are predators.

• These animals have relatively long life-cycles.

• Once populations decline, they take a long time to recover.

Tillage Impact on Earthworm Populations

• Numbers of earthworms were reduced by 58% when the soil was tilled prior to planting sugarcane.

Tillage Disturbs Natural Systems of Biological Control

• The trapping networks produced by nematode-trapping fungi are destroyed by tillage and it takes time and energy to re-establish them.

Detrimental Effects of Tillage on Soil

• Tillage has disastrous effects on soil carbon and the soil biology. If the ecosystem services provided by soil organisms are to be retained, tillage must be minimised.

Soil Compaction from Farm Machinery

• Random traffic from farm machinery is a major issue.

• Sugarcane is one of the best examples:

  • Row spacings were generally 1.5 m.

  • Wheel spacings on harvest machinery and haulouts were usually 1.85 m.

  • Compaction problems were widespread and compounded by harvesting when the soil is wet.

Soil Compaction in Sugarcane

• Most of the surface area is compacted when row and wheel spacings do not match (e.g., 1.5 m rows and 1.85 m wheel spacings).

• Root growth is reduced by 50% when soil strength reaches 2000 kPa.

Combined Damage from Tillage and Compaction

• Disastrous for microarthropods.

Monoculture and Limited Crop Diversity

• Common in agriculture.

• Crop-specific pathogens become dominant:

  • Panama disease of banana

  • Take-all of cereals

  • Pachymetra root rot of sugarcane

  • Potato cyst nematode

Bare Fallows Deplete Soil Organic Matter

• Loss of organic matter results in poor soil health.

• Examples:

  • Continual vegetable crops with bare fallow between crops.

  • Early formation of plastic-covered beds for vegetables.

  • Long fallows to store water for winter cereal crops.

Removal of Surface Residues

• Surface residues should be retained rather than being burnt or sold.

• Organic mulch provides carbon inputs and other benefits:

  • Protects the soil from wind and water erosion.

  • Improves soil moisture conditions.

  • Dampens temperature fluctuations.

  • Provides a home for a diverse range of soil organisms.

Detrimental Effects of Fertilizer Inputs

• Nitrogen inputs usually decrease fungal biomass and diversity.

• Omnivorous nematodes are sensitive to nitrogen inputs.

• High phosphorus levels are detrimental to mycorrhizal fungi.

• Worst-case scenario: high nutrient inputs at a single time.

• Best practices: frequent fertilizer applications at low rates, controlled-release fertilizers, regular nutrient inputs via trickle irrigation.

Off-Target Effects of Pesticides

• Imidacloprid:

  • Decimates earthworm populations.

  • Is detrimental to predatory arthropods.

  • Nectar and pollen from treated plants are toxic to honey bees.

• Copper:

  • Long-term use of copper fungicides in avocadoes has decimated earthworm populations.

• Soil fumigants:

  • Create a biological vacuum by killing all beneficial organisms.

• Herbicides:

  • Indirectly reduce the diversity and abundance of beneficial arthropods by killing plants.

Integrated Pest and Disease Management (IPM)

• Multiple tactics are used to control pests, including:

  • Quarantine, biosecurity.

  • Pest monitoring and action based on damage thresholds.

  • Preventative cultural practices (crop rotation, cover crops, intercropping, removal of diseased plants).

  • Resistant and tolerant varieties.

  • Optimal irrigation and nutrient management.

  • Biological controls.

• In IPM, pesticides are used as a last resort.

Improving Biological Health of Agricultural Soils

Management Practices to Improve Soil Health

• Key practices:

  • Continuous inputs of organic matter (from plants).

  • Permanent cover of plant residues.

  • A diverse rotation sequence.

  • Minimum tillage.

  • Avoidance of compaction through traffic control.

• Second-tier practices:

  • Biomass-producing cover crops.

  • Legumes in the farming system.

  • Integration of crops and livestock.

  • Organic mulches and amendments.

  • Improved nutrient-use efficiency.

  • Site-specific management of inputs.

  • Integrated pest management.

Sugarcane Farming System

• Five key practices integrated into the farming system:

  • Row spacing and machinery wheel spacings are matched for controlled traffic.

  • Tillage is minimised.

  • Rotation crops, such as soybean and peanut, are included.

  • Land is never bare fallowed.

  • Crop residues are retained as a trash blanket.

Benefits of the Sugarcane Farming System

• Soil health:

  • Less compaction.

  • More carbon and labile carbon.

  • Higher rainfall infiltration rates.

  • Reduced surface crusting and improved aggregate stability.

  • Increased water-holding capacity.

  • Reduced soil losses due to erosion.

  • Higher cation-exchange capacity.

  • Reduced pathogen loads.

• Economic:

  • Productivity maintained.

  • Reduced tractor hours.

  • Lower fuel costs.

  • Fewer labor inputs.

  • Additional income from grain.

  • Lower fertilizer costs (due to legumes).

  • Improved timeliness of operations.

  • Fewer pesticide inputs.

Conservation Agriculture in the Grains Industry

• Prior to 1980, Australian grain-growing soils were routinely tilled, leading to soil moisture loss and erosion.

• Conservation agriculture was introduced in the 1980s, including:

  • Minimal tillage.

  • Crop rotation.

  • Retention of crop residues on the soil surface.

• By 2016, 74% of grain crops were sown using zero till or no till.

• Benefits included increased soil carbon levels, better soil structure and rainfall infiltration, soil moisture retention, and enhanced soil biological diversity.

Vegetable Production

• Traditional methods often follow a “biological desert” philosophy:

  • Soil fallowed

  • Few carbon inputs

  • Frequent tillage

  • High pesticide inputs

  • Plastic ‘mulch’

  • High N inputs

  • Soilborne pathogens managed with soil fumigants and nematicides

Improved Vegetable Production Systems

• Some growers have modified their farming system and improved soil health, e.g., through permanent bed systems.

Permanent Bed Systems for Tomato Production

• Trash planter used for cutting through trash and sowing cover crop

• Permanent beds with centrosema cover crop during summer

• Roll cover crop and spray out with herbicide

• Transplant tomatoes through mulch

Benefits of Permanent Bed Systems

• Soil compaction was reduced after 4 years no-till

• Earthworm numbers increased after 4 years no-till

• Improved soil biology

Biomass Mulching Systems

• Bob Euston’s bean and squash production system incorporates biomass production, mulching, minimum till and permanent ground cover

Improving the Sweetpotato Production System

• Root-knot nematode causes severe damage.

  • Although nematicides are widely used, yield is often reduced by 75%.

• Poor soil health due to excessive tillage:

  • To remove root-knot nematodes and other soilborne pathogens.

  • During harvest.

  • To flatten beds before planting rotation crops.

Field Trials to Improve Sweetpotato Soil Health

• Trial where beds were formed early to kill volunteers and forage sorghum was planted to retain biomass and prevent erosion.

Organic Amendments to Control Root-Knot Nematode

• Four amendments to V-furrows in December 2018:

  • Nil

  • Compost

  • Sawdust

  • Sawdust/chicken litter

• Application rate: 6 L/m row.

Results of Organic Amendments Trial

• 7 weeks after planting:

  • Roots growing in the sawdust/chicken litter treatment had very few galls and less damage.

  • Compost and sawdust also reduced galling.

• At Harvest:

  • Sawdust and the sawdust/chicken litter mixture both reduced
    root-knot nematode damage

  • Marketable yield increased by 29%.

• Future challenge
  Develop a farming system in which beds are formed early, nematode
  resistant rotation crops are grown on the beds, organic amendments
  are applied, and sweetpotato is planted with minimal soil disturbance

Summary of Management Practices and Soil Health

• Tactics that reduce soil health:

  • Frequent or aggressive tillage

  • Bare fallows

  • Monoculture

  • Random machinery traffic

  • Removal of crop residues

  • High inputs of inorganic fertilisers at a single time

  • Herbicides and mechanical weed control

  • Chemical control of pests and diseases

• Tactics that promote soil health:

  • No till, minimum till

  • Cover crops

  • Diverse rotations, intercrops, pasture

  • Controlled traffic

  • Retention of crop residues as mulch

  • Organic amendments, split fertiliser applications, controlled-release formulations

  • Weeds controlled primarily by mulching and/or cultural methods

  • Integrated pest management

The challenge is to incorporate ALL these tactics into ALL farming systems