The components of agricultural sustainablity

Question 1

The components of agricultural sustainability

Answer 1

Soil and land
Nutrients
Water use
Organic matter
Biota
Energy and agrochemicals
Crop productivity- food supply
People
Climate and ecosystems

Question 2

Fossil fuel use is driving climate change- this will decrease the land area and soil quality and volumes suitable for crops as a result of rising sea levels and effects on water availability, and damage to soils from salinization.

Answer 2

Replacing fossil fuels with some kinds of biofuels will often compete with crops for land area and fertile soils but may reduce effects of energy use on climate change.

Question 3

Decreasing numbers and effectiveness of herbicides, fungicides and pesticides threatens yields.

Answer 3

Climate change therefore is likely to derive down yields and increase crop vulnerability to failure.

Question 4

Whilst more fertilizer use can increase yields it often contributes to greenhouse gas emissions.

Answer 4

Crop pests and diseases are worse when crops are stressed, and effects of climate change are predicted to increase pests and diseases and decrease crop yields directly.

Question 5

Estimated 200-400 million more at risk of hunger by 2080 due to climate change

Answer 5

Battisti and Naylor (2009)

Question 6

Soil

UK: Most arable fields step down from their margins

Answer 6

A few generations of farmers destroyed the topsoil of vast areas of N America

Anticipated soil losses in future: climate change- extreme weather- drought / high rainfall erosion events
Warming – increased decomposition of soil organic matter.

Question 7

Hundreds of millions of people live on fertile land just above sea level and these are areas important for food production-

Answer 7

Bangladesh, Florida, Netherlands (large area below sea level), Nile delta etc.
Where will they move to?
What area will change from agriculture to housing to accomodate this?

Question 8

Displacement of up to 187 million people– loss of fertile deltas and coastal plains with 2 m rise in sea level.

Answer 8

nicholls et al 2011

Question 9

Components of agricultural sustainability

Soil conservation technologies:
No-till cultivation, strip-cropping, contour planting, terracing, mulches, cover crops, leys, agro-forestry, and wind-breaks. Water management- to store water in soil (mulches, organic matter, terracing)

Answer 9

Winter cover-crop of black oats and phacelia

Many techniques try to mimic natural ecosystems: complete vegetation cover gives very low soil losses.

Question 10

Components of agricultural sustainability
2. Nutrients

Legumes and green-manures in rotations to build and retain fertility.
Agro-forestry especially with legume trees

Phosphorus mobilizing plants, mycorrhizas and bacteria- use of cultivation techniques and inoculants to achieve these goals.

Answer 10

Use of rock-dust fertilization from abundant rock sources like basalt- especially using rock dust waste as a by-product of mining for other uses such as roadstone.

Waste recycling, composting and manures
organic matter nutrient storage, and ion exchange capacity

Question 11

Phosphate fertilizer is being added at much greater rates than crops use it- most becomes bound in the soil- but more needs to be added because in modern intensive agriculture P use is inefficient.

Answer 11

Erosion losses of P enriched topsoil-represents an irreplaceable loss of a non-renewable nutrient. At the same time, in developing countries the cost of P fertilizer that can massively increase yields with modest additions is too expensive!

Question 12

Australia: highly weathered oxisol amended with ground basalt

Basalt reduces P sorption, increases available P and reduces soil acidity

Answer 12

74% of the > 1200 mm rainfall zone is strongly acid, and the remainder is medium acid or acid. Sugar growing areas occur in this zone and requires regular liming or other alkaline inputs for long term sustainability

Question 13

Under irrigation UK wheat growing can yield 11.5-14.8 Tonnes per hectare.

UK per capita wheat consumption
Is about 74 kg per person per year.

At 13 tonnes per hectare we can produce enough wheat to feed over 150 people per hectare at current consumption.

At 13 tonnes per ha UK land allocated to wheat could support 346 million people at current UK consumption.

Answer 13

Infrastructure requirements for rainwater harvesting and storage in the west and irrigation in the east.
Rain and snow-melt and groundwater
Irrigation often requires pumping- frequently using groundwater resources at rates that are unsustainable- energy and water supply implications

Question 14

Salt accumulation in soils where irrigation practices are poor- destroys soil

Solar powered desalination of seawater for irrigation

Answer 14

Desalination- reverse osmosis, and solar power to replace fossil fuels

https://www.un-ihe.org/sites/default/files/19_jrc_procworkshopwaterenergyfoodecosystemsnexusandsdgs.pdf#page=21

Question 15

Organic matter

Answer 15

Conserving and accumulating organic matter in soil- reduces erosion, increases water and nutrient storage, helps reduce atmospheric CO2 concentrations, increases soil aggregate size and stability, increases crop yields.

Question 16

Managing soil for long-term productivity

The importance of soil organic matter

Answer 16

An increase by 1 t C ha-1 yr-1 in the SOC pool within the root zone can enhance food production in developing countries by 30-50 Mt year-1 (Lal et al., 2003)

24-40 Mt year-1 of cereal and legumes,
6-10 Mt year-1 of roots and tubers.

Question 17

Key questions
How feasible is it to substantially increase soil organic carbon storage in agriculture?

What are the optimal strategies to rapidly accumulate soil organic carbon?

Agroforestry
Leys
Legumes

Answer 17

If leys are reintroduced into rotations and no-tillage management employed will this build larger long-term carbon stocks than ploughing up short-term leys?

How stable will the carbon be – will climate change including warming result in increased rates of loss of soil organic carbon including from natural ecosystems?

Question 18

5. Biota Pests, disease and weeds
   Conventional intensive agriculture is failing:
   Resistance to chemicals and banning of use of some chemicals presents increasing problems for crop production.
   Diverse cropping systems and rotations to reduce build-up of diseases and pests.
   Inducible defences (e.g. by mycorrhiza-induced systemic resistance).

Answer 18

Facilitating or adding natural enemies of pests

Question 19

Components of agricultural sustainability

5. Beneficial biota

Answer 19

Nutrient cycling:
Legumes and green-manures fixing and recycling nitrogen
Crop rotation, cover cropping and co-cropping (e.g. cereals undersown with clover)
Phosphorus mobilizing plants,
Phosphorus solubilizing bacteria and other microorganisms
Mycorrhizas and plant growth promoting rhizobacteria
Soil structure, aggegation, drainage and C sequestration:
Earthworms
Mycorrhizas
Leys and legumes, cover crops, agro-forestry.

Question 20

Relationships among light distribution, radiation use efficiency and land equivalent ratio inmaize-spybean strip intercropping Liu et al 2018: By adjusting distances between rows they found the optimal gap width for growing soybeans is 1.6 m-1.8 m, and the best maize row distance is 0.4 m.

Answer 20

Optimal planting achieved a Land Equivalent Ratio of 1.42, representing world-leading values.

The optimal planting for dual cropping was maize row distance of 0.4 m, soybean row distance 0.4 m, and distance between maize and soybean rows of 0.6m.

Question 21

Our lifestyle is currently almost totally oil dependent
Pretty et al. (2005).

Nearly 30% of UK goods vehicle miles are used to transport agri-food products

Answer 21

80-95% of all transport is fuelled by oil products
70-75% of all oil is used for transportation
95% of all goods in the shops get there using oil
99% of our food involves oil or gas for fertilisers, agrochemicals, tilling, cultivation and transport
Our economy and food supply depends on cheap oil

Question 22

Components of agricultural sustainability

7. Crop productivity- food supply

Answer 22

Depends on all these fabctors- and the weather!

Soil
Nutrients
Organic matter
Biota – beneficial and harmful
Water use
Energy
People

Question 23

Food supply is dependant on how we use production-

whether we use cereals as human food, feed for animals for meat, or to produce biofuel to add to petrol or diesel. T

Answer 23

otal grain production currently is more than double human consumption- more is fed to animals than humans. Increasing use for industrial products like biofuels.

Question 24

8. People. Farmers are our vital stewards of the land, managers of our agri-ecosystems and producers of our food. How much do we value these workers on whom our lives depend?

Answer 24

Despite our success in food production (53% self-sufficient in the UK by 1% of the population) we are failing to attract young people into studying the underpinning science or entering farming as a career:

How can we expect 59 year old farmers to suddenly abandon the unsustainable cropping systems and approaches that they have spent their lives developing to maximise short-term yield?

Plant Science has almost disappeared from British universities, with degree applications crashing to an all time low of just 26 nationally in 2009.

There are now no departments of soil science or undergraduate degrees in soil science.

I was asked to take the word ’soil’ out of the title of this module because of decreasing numbers of students chosing the module. Changing the name increased student numbers by more than 300%.

Question 25

If we want to protect soils we need to reward and incentivise farmers
Don’t forget- most farms in the UK are family businesses and on average are receiving low incomes and need subsidy to survive.

Answer 25

> 60% earn less than £25,000
National minimum wage for 70 hours a week = £24,388 Many farmers work 100 hours a week
Office for national statistics – 50 year old men earn an average of £15.54 per hour = £32,000 for a 40 h week

Question 26

Sustainable agriculture requires sustainable incomes for farmers- so that they can afford to invest in long-term protection of soil and ecosystems. Unless farmers are paid directly for ecosystem services and sustainability or properly rewarded for the food they produce they will not be able to chose environmental sustainability over short-term economic survival.

Answer 26

Livestock farming- making a net loss- supported by EU funded environmental and farm payment (land area) subsidies, and a tiny diversified income (e.g. renting properties to tourists).
Cereals and mixed farming also often making a loss on production- varies from year to year

Question 27

8. People

Food wastage
In the UK alone food worth over £10,000,000,000 is wasted each year
It accounts for 5% of UK’s greenhouse gas emissions

Answer 27

”There are nearly a billion people malnourished in the world but all of them could be lifted out of hunger with less than a quarter of the food wasted in Europe and North America. In a globalised food system, where we are all buying food in the same international market place, that means we’re taking food out of the mouths of the poor” Tristram Stuart

Question 28

Why tackling waste should be a higher priority than intensification and producing more.

Answer 28

Food waste is a major loss of efficiency and resources. Ultimately the consumer pays for waste and so it is in their interest to minimize it- but it is in the supermarket / suppliers interest to sell us even more!

Question 29

In the UK 18-20 M tonnes of food are wasted each year, 8.3 M tonnes thrown away in domestic waste of which 65% is avoidable (Defra 2010).

Answer 29

Halving household food waste would be equivalent to taking 1 in 8 cars off the road in terms of reduced greenhouse gas emissions (Defra 2010).

Question 30

A few blades of grass in baby spinach- crop ploughed in – not wanted by supermarkets (because not wanted by consumers)

Answer 30

Fish catch discard waste
Sell-by date waste
Appearance-rejection waste by supermarket