Food, Soil, and Pest Management Chapter 12

Soil: the foundation for agriculture  Land devoted to agriculture covers 38% of Earth’s land surface  Agriculture = practice of raising crops and livestock for human use and consumption  Cropland = land used to raise plants for human use  Rangeland or pasture = land used for grazing livestock  Soil = a complex plant-supporting system consisting of disintegrated rock, organic matter, water, gases, nutrients, and microorganism It is a renewable resource

Soil as a system  Soil consists of mineral matter, organic matter, air, and water and is formed by: Dead and living microorganisms, and decaying material Bacteria, algae, earthworms, insects (decomposers), mammals, amphibians, and reptiles (burrowing animals) Since soil is composed of living and non-living matter, it is considered an ecosystem

Soil formation is slow and complex  Parent material = the base geologic material of soil Mostly rock and sediments Derived from weathered bedrock in unglaciated areas  Weathering = the physical, chemical, or biological processes that break down rocks to form soil Physical (mechanical) = wind and rain, no chemical changes in the parent material Chemical = substances chemically interact with parent material Biological = organisms break down parent material

Weathering produces soil

Other processes affect soil formation  Erosion = the movement of soil by wind or water Removes topsoil Occurs when vegetation is absent  Biological activity includes deposition, decomposition, and accumulation of organic matter Humus = a dark, spongy, crumbly mass of organic material formed by partial decomposition

A soil profile consists of horizons  Horizon = each layer of soil  Soil profile = the cross- section of soil as a whole  Up to six major horizons may occur in a soil profile Topsoil = inorganic and organic material most nutritive for plants (A) Leaching = dissolved particles move down through horizons (E to B)

Soils are characterized in many ways  Soils are classified based on color, texture, structure, and pH  Soil color = indicates its composition and fertility Black or dark brown = rich in organic matter Pale gray or white = indicates leaching  Soil texture = determined by the size of particles From smallest to largest = clay, silt, sand Loam = soil with an even mixture of the three Influences how easy it is to cultivate and let air and water travel through the soil (porosity & permeability)

Soil texture classification Silty soils with medium- size pores, or loamy soils with mixtures of pore sizes are best for plant growth and crop agriculture

Soil structure  Soil structure = a measure of soil’s “clumpiness” Large clumps can discourage plant roots (tend to be higher in clay) Repeated tilling compacts soil, decreasing its water- absorbing capabilities (permeability) Plowpan = a hard layer resulting from repeated plowing that resists water infiltration and root penetration

Soil pH  Soil pH = influences a soil’s ability to support plant growth Soils that are too acidic or basic can kill plants Soils deficient of humus have a higher pH As rain water percolates down through the humus it forms tannic acid from dead leaves and bark. This weak acid has a pH of about 6.

Cation exchange is vital for plant growth  Cation exchange = process that allows plants to gain nutrients Negatively charged soils hold cations (positively charged ions) of Ca+, Mg+, and K+  Cation exchange capacity = a soil’s ability to hold cations, preventing them from leaching, thereby increasing their availability to plants A useful measure of soil fertility Greatest in fine soils Diminishes with lower pH

Regional differences in soils affect agriculture  Rainforests have high primary productivity, but when cleared rain leaches minerals and nutrients deeper into the soil, reducing their accessibility to roots Swidden agriculture = cultivation of a plot for a few years and then letting it regrow into forest  Temperate grasslands (prairies) have lower rainfall and less nutrient leaching thus higher productivity Prairie profile

Erosion degrades ecosystems and agriculture  Erosion increases through: excessive tilling, overgrazing, and clearing forests (anything that exposes the soil)  In agriculture the greatest concern is the removal of topsoil (no topsoil = poor crop growth)

Soil erodes by several methods  Removing plants accelerates erosion  Rill erosion moves the most topsoil, followed by sheet and splash forms of erosion  Water erosion occurs most easily on steep slopes  Erosion in the U.S. declined between 1982 and 2001 Soil conservation measures Despite conservation measures, the U.S. still loses 6 tons of soil for every ton of grain harvested

Various types of soil erosion Splash Sheet Rill Gully

Soil erosion is a global problem  Humans are the primary cause of erosion It is occurring at unnaturally high rates  In Africa, erosion over the next 40 years could reduce crop yields by half Coupled with rapid population growth, some observers describe the future of agriculture as a crisis situation

Desertification  Desertification = a loss of more than 10% productivity Erosion, soil compaction, forest removal, overgrazing, salinization, climate change, depletion of water sources  Most prone areas = arid and semiarid lands

Desertification has high costs  Desertification affects 1/3 of the planet’s land area In over 100 countries  Costs tens of billions of dollars each year China loses over $6.5 billion/year alone from goat overgrazing In Kenya, 80% of the land is vulnerable to desertification from overgrazing and deforestation

The Dust Bowl  In the late 19 th and early 20th centuries, settlers arrived in Oklahoma, Texas, Kansas, New Mexico and Colorado  Grew wheat, grazed cattle Removed vegetation  A drought in the 1930s made conditions worse  Thousands of farmers left their land and had to rely on governmental help

Shelterbelts Shelterbelts were planted extensively after the Dust Bowl. Fast growing trees such as the Lombardy Poplar break the force of the wind and help stabilize soil.

The Soil Conservation Service  Started in 1935, the Service works with farmers to develop conservation plans for farms Prepare an integrated plan Implement conservation measures  Conservation districts = districts operate with federal direction, authorization, and funding, but are organized by the states  Natural Resources Conservation Service = 1994 renaming of the Soil Conservation Service Expanded responsibilities include water quality protection and pollution control

Protecting soil: crop rotation and contour farming  Crop Rotation = alternating the crops grown from one season to the next, Cover crops protect soil when main crops aren’t planted Wheat or corn and soybeans  Contour Farming = plowing furrows sideways across a hillside, perpendicular to its slope, to prevent rills and gullies

Protecting soil: terracing and intercropping  Terracing = level platforms are cut into steep hillsides, sometimes with raised edges A “staircase” to contain water reduces erosion  Intercropping = planting different types of crops in alternating bands or other spatially mixed arrangements Increases ground cover

Protecting soil: shelterbelts and reduced tillage  Shelterbelts or Windbreaks = rows of trees or other tall, perennial plants that are planted along the edges of fields to slow the wind Alley cropping = shelterbelts + intercropping  Reduced Tillage = furrows are cut in the soil, a seed is dropped in and the furrow is closed No-till farming disturbs the soil even less

No-till agriculture in Southern Brazil  Southern Brazil’s climate and soils make for bountiful harvests but repeated planting has diminished the productivity of the soil  Leaving crop residues on their fields after harvesting and planting “cover crops” reduced erosion, increased yields and cut cost

Pros and cons of no-till farming  Almost half of U.S. farmland uses no-till farming  Benefits: reduced soil erosion, greater crop yields, enhanced soils  Negatives: increased use of herbicides and fertilizers  But, green manure (dead plants and fertilizer) and rotating crops minimizes the negatives

Plant cover reduces erosion  Eroding banks along creeks and roadsides are stabilized by planting plants to anchor soil  China has the world’s largest tree-planting program It does slow erosion But it does not create ecologically functional forests, because monocultures are planted

Irrigation: boosted productivity, but problems, too  Irrigation = Artificially providing water to support agriculture Unproductive regions become farmland  Waterlogging = over-irrigated soils Water suffocates roots  Salinization = the buildup of salts in surface soil layers Worse in arid areas Salinization inhibits production of 20% of all irrigated cropland, costing more than $11 billion/year

Salinization prevention  It is easier and cheaper to prevent salinization than fix it  Do not plant water-guzzling crops in sensitive areas  Irrigate with low-salt water  Irrigate efficiently, supplying only water that the crop requires Drip irrigation targets water directly to plants

Fertilizers boost yields but cause problems  Fertilizer = substances that contain essential nutrients  Inorganic fertilizers = mined or synthetically manufactured mineral supplements  Organic fertilizers = the remains or wastes of organisms manure, crop residues, fresh vegetation Compost = produced when decomposers break down organic matter Never add waste from butchering animals to compost Applying synthetic fertilizer, vs. Planting rye, a “green manure”

Overapplication of Fertilizer  Inorganic fertilizer use has skyrocketed  Overapplying fertilizer can ruin the soil and severely pollute several areas  Runoff causes eutrophication in nearby water systems  Nitrates leach through soil and contaminate groundwater  Nitrates can also volatilize (evaporate) into the air

Environmental effects of over-fertilizing

Overgrazing causes soil degradation  Overgrazing = too many animals eat too much of the plant cover Impedes plant regrowth  A leading cause of soil degradation  Government subsidies provide few incentives to protect rangeland 70% of the world’s rangeland is classified as degraded

U.S. programs promote soil conservation  Food Security Act of 1985: Farmers that adopt soil conservation plan receive price supports and other benefits  Conservation Reserve Program (1985) Farmers are paid to place highly erodible land into conservation reserves Trees and grasses are planted instead of crops Saves 771 million tons of topsoil per year Generates income for farmers Provides habitat for native wildlife

Federal Agricultural Improvement Act (1996)  Known as the Freedom to Farm Act Aimed to reduce subsidies and government influence over farm products Created the Environmental Quality Incentive Program and Natural Resource Conservation Foundation Promotes and pays for conservation practices in agriculture  Low-Input Sustainable Agriculture Program (1998) Provides funding for sustainable agricultural practices for individual farmers

International soil conservation programs  Food and Agriculture Organization (FAO) = the United Nations’ main agricultural program  The FAO’s Farmer-Centered Agricultural Resource Management Program (FAR)… Helps farmers duplicate agricultural success stories Uses local communities to educate and encourage farmers to conserve soils and secure the food supply Supports innovative approaches to resource management and sustainable agriculture in around the world China, Thailand, Vietnam, Indonesia, Sri Lanka, Nepal

Today, we are producing more food per person  Food production currently exceeds population growth  We produce food through technology Fossil fuels, irrigation, fertilizer, pesticides, crossbreeding  Predictions of mass starvation in 1960s did not happen

Food security  Food security = the guarantee of adequate and reliable food supply to all people at all times  Fewer people today are hungry than in 1970  We have reduced hunger by half since 1970 But, 850 million people still go hungry Since 1985, world grain production has fallen by 9%

We face both too little and too much food  Undernourishment = people receive less than 90% of their daily caloric needs Mainly from economic reasons in developing countries 31 million Americans are food insecure  Overnutrition = receiving too many calories In the U.S., 25% of adults are obese Worldwide, more than 300 million people are obese  Malnutrition = a shortage of nutrients the body needs The diet lacks adequate vitamins and minerals

Many People Suffer from Chronic Hunger and Malnutrition  Macronutrients Carbohydrates Proteins Fats  Micronutrients Vitamins Minerals

Many People Do No Get Enough Vitamins and Minerals  Most often vitamin and mineral deficiencies in people in developing countries  Iron  Vitamin A  Iodine  Golden rice

Malnutrition  Vitamin A deficiency in some developing countries leads to Blindness Death  1999: Porrykus and Beyer Genetically engineered rice with beta-carotene and more iron  Is this the answer for malnutrition in these countries?  Challenge of increased food production

Acute Food Shortages Can Lead to Famines  Famine Usually caused by crop failures from Drought Flooding War Other catastrophic events

Many People Have Health Problems from Eating Too Much  Overnutrition  Similar health problems to those who are underfed Lower life expectancy Greater susceptibility to disease and illness Lower productivity and life quality

Quantity and quality of food is important  Kwashiorkor = diets lacking protein or essential amino acids Occurs when children stop breast-feeding Bloated stomach, mental and physical disabilities  Marasmus = protein deficiency and insufficient calories Wasting or shriveling of the body

The green revolution  Dramatically increased per-acre yields  Spread to the developing world in the 1940s with wheat, rice, corn  Depended on large amounts of Synthetic fertilizers Chemical pesticides Irrigation Heavy equipment

The green revolution brought benefits and harm  From 1900 to 2000, cultivated area increased 33%, while energy inputs increased 80 times!  Positive effects on natural resources Prevented some deforestation Preserved biodiversity  Negative effects on natural resources Pollution Erosion Salinization Desertification

The green revolution in India  Between 1961 and 2003 Population increased 100% Food production increased 150% As a result of the green revolution, India became a grain exporter

Monocultures increase output, but at a cost  Monoculture = a large expanse of a single crop More efficient, increases output Devastates biodiversity Susceptible to disease and pests  Narrows human diet: 90% of our food comes from 15 crop species and 8 livestock species Armyworms easily defoliate monocultures

Pests and pollinators  Pest = any organism that damages valuable crops  Weed = any plant that competes with crops  Pesticides = poisons that target pest organisms Insecticides = target insects Herbicides = target plants Fungicides = target fungi  400 million kg (900 million lbs.) of pesticides are applied in the U.S. each year 75% of this is applied to agricultural land Usage is increasing in developing countries

Resistance to pesticides  Some individuals are genetically immune to a pesticide - They survive and pass these genes to their offspring  Pesticides stop being effective - Evolutionary arms race: chemists increase chemical toxicity to compete with resistant pests

Biological control  Biological control (Biocontrol) = uses a pest’s natural predators to control the pest Reduces pest populations without chemicals Cactus moths control prickly pear Bacillus thuringiensis (Bt) = soil bacteria that kills many pests

Biocontrol agents may become pests themselves  No one can predict the effects of an introduced species  The agent may have “nontarget” effects on the environment and surrounding economies Cactus moths are eating rare Florida cacti  Removing a biocontrol agent is harder than halting pesticide use Due to potential problems, proposed biocontrol use must be carefully planned and regulated

Integrated Pest Management (IPM)  IPM uses multiple techniques to suppress pests - Biocontrol - Chemicals, when necessary - Population monitoring - Habitat alteration - Crop rotation and transgenic crops - Alternative tillage methods - Mechanical pest removal Within 4 years of using IPM in Indonesia, rice yields rose 13%, and $179 million saved by phasing out subsidies

We depend on insects to pollinate crops  Not all insects are pests; some are absolutely vital 800 cultivated plant species rely on insect pollinators  Pollination = male plant sex cells fertilize female sex cells By wind or animals  Pollinators include: Hummingbirds Bats Insects Flowers are evolutionary adaptations to attract pollinators

Conservation of pollinators is vital  Native populations of pollinators have plummeted  Honeybees pollinate more than 100 crops – 1/3 of the U.S. diet. - In 2006, hives died off  To conserve bees: - Reduce or eliminate pesticide use - Plant flowering plants

Genetically modified organisms  Genetic engineering = laboratory manipulation of genetic material  Genetically modified organisms = organisms that have been genetically engineered by …  Recombinant DNA = DNA created from multiple organisms

Genetic engineering has both benefits and risks  Benefits of genetic engineering: Increased nutritional content Increased agricultural efficiency Rapid growth Disease and pest resistance  Negatives of genetic engineering: Risks are not yet defined or well understood Protests from environmental activists, small farmers, and consumer advocates

Biotechnology is impacting our lives  Biotechnology = the material application of biological science to create products derived from organisms  Transgenic organism = an organism that contains DNA from another species Transgenes = the genes that have moved between organisms  Biotechnology has created medicines, cleaned up pollution, and dissolves blood clots

Some genetically modified foods

Genetic engineering versus agricultural breeding  Artificial selection has influenced the genetic makeup of livestock and crops for thousands of years  Proponents of GM crops say GM foods are safe  Critics of GM foods say: Traditional breeding uses genes from the same species Selective breeding deals with whole organisms, not just genes In traditional breeding, genes come together on their own Traditional breeding changes organisms through selection, while genetic engineering is more like the process of mutation

Biotechnology is changing our world  GM foods become big business  Most GM crops are herbicide resistant Farmers apply herbicides to kill weeds, and crops survive Most U.S. soybeans, corn, cotton, and canola are genetically modified Globally, more than 10 million farmers grew GM foods on 102 million ha of farmland, producing $6.15 billion worth of crops

What are the impacts of GM crops?  As GM crops expanded, scientists and citizens became concerned Dangerous to human health Escaping transgenes could pollute ecosystems and damage nontarget organisms Pests could evolve resistance Could ruin the integrity of native ancestral races Interbreed with closely related wild plants

Supporters maintain that GM crops are safe  Supporters make the following points: GM crops pose no ill health effects They benefit the environment by using less herbicides Herbicide-resistant crops encourage no-till farming GM crops reduce carbon emissions by needing fewer fuel-burning tractors and sequestering carbon in the soil by no-till farming  Critics argue that we should adopt the precautionary principle = don’t do any new action until it’s understood

Studies on GM foods show mixed results  Between 2003 and 2005, the British government commissioned three large-scale studies, which showed GM crops could produce long-term financial benefits Little to no evidence was found of harm to human health, but effects on wildlife and ecosystems are not well known Bird and invertebrate populations in GM fields were mixed; some crops showed more diversity, some less, depending on the crop

The GM debate involves more than science  Ethical issues plays a large role People don’t like “tinkering” with “natural” foods With increasing use, people are forced to use GM products, or go to special effort to avoid them Multinational corporations threaten the small farmer Research is funded by corporations that will profit if GM foods are approved for use Crops that benefit small, poor farmers are not widely commercialized The GM industry is driven by market considerations of companies selling proprietary products

GMO producers are suing farmers  Monsanto has launched 90 lawsuits against 147 farmers, winning an average $412,000 per case Monsanto charged farmer Percy Schmeiser of Canada with using its patented GM seeds without paying for them Schmeiser charged the seeds blew onto his field from the neighbor’s adjacent field The courts sided with Monsanto, saying Schmeiser had violated Monsanto’s patent Farmers say that “[they] are being sued for having GMOs on their property that they did not buy, do not want, will not use, and cannot sell”

Nations differ in their acceptance of GM foods  Europe opposed GM foods The U.S. sued the European Union before the World Trade Organization, charging that the European Union was hindering free trade Brazil, India, and China approve GM crops Zambia refused U.S. food aid, even though people were starving, because some seeds were genetically modified

Preserving crop diversity: insurance against failure  Preserving native variants protects against crop failure Monocultures are vulnerable, so wild relatives contain genes that could provide resistance to disease and pests  We have already lost a great deal of genetic diversity in crops Wheat varieties in China dropped from 10,000 (1949) to 1,000 (1970s)  Market forces discourage diversity in food’s appearance Consumers prefer uniform, standardized food

Preserving crop diversity: seed banks  Seed banks = institutions that preserve seed types as a kind of living museum of genetic diversity Seeds are collected and preserved, and periodically planted Funding is not adequate for these facilities The Royal Botanic Garden’s Millennium Seed Bank in Britain holds more than 1 billion seeds

Eating animal products has significant impacts  As wealth and commerce increase, so does consumption of meat, milk, and eggs Global meat production has increased fivefold Per capita meat consumption has doubled Domestic animal production for food increased from 7.3 billion in 1961 to 20.6 billion in 2000

Feedlot agriculture  Feedlots (factory farms) = also called Concentrated Animal Feeding Operations (CAFOs) Huge warehouses or pens designed to deliver energy- rich food to animals living at extremely high densities Over ½ of the world’s pork and poultry come from feedlots Debeaked chickens spend their lives in cages; U.S. farms can house hundreds of thousands of chickens in such conditions

The benefits and drawbacks of feedlots  The benefits of feedlots include: Greater production of food Unavoidable in countries with high levels of meat consumption, like the U.S. They take livestock off the land and reduces the impact that they would have on it  Drawbacks of feedlots include: Contributions to water and air pollution Poor waste containment causes outbreaks in disease Heavy uses of antibiotics to control disease

Energy choices through food choices  90% of energy is lost every time energy moves from one trophic level to the next  The lower on the food chain from which we take our food sources, the more people the Earth can support.  Some animals convert grain into meat more efficiently than others

Environmental ramifications of eating meat  Land and water are needed to raise food for livestock  Producing eggs and chicken meat requires the least space and water Producing beef requires the most When we choose what to eat, we also choose how we use resources

Aquaculture  World fish populations are plummeting Technology and increased demand  Aquaculture = raising aquatic organisms for food in a controlled environment Aquatic species are raised in open-water pens or land-based ponds

Aquaculture is growing rapidly  The fastest-growing type of food production Provides a third of the world’s fish for human consumption Most widespread in Asia

The benefits and drawbacks of aquaculture  Benefits: A reliable protein source Sustainable Reduces fishing pressure on overharvested wild fish stocks Energy efficient  Drawbacks: Diseases can occur, requiring expensive antibiotics Reduces food security Large amounts of waste Farmed fish may escape and introduce disease into the wild

Sustainable Agriculture  Industrial agriculture may seem necessary, but less- intensive agricultural methods may be better in the long run  Sustainable agriculture = does not deplete soil, pollute water, or decrease genetic diversity  Low-input agriculture = uses smaller amounts of pesticide, fertilizers, growth hormones, water, and fossil fuel energy than industrial agriculture  Organic agriculture = Uses no synthetic fertilizers, insecticides, fungicides, or herbicides Relies on biological approaches (composting and biocontrol)

A standardized meaning for “organic”  People debate the meaning of the word “organic” Organic Food Production Act (1990) establishes national standards for organic products The USDA issued criteria in 2000 by which food could be labeled organic Some states pass even stricter guidelines for labeling

The market for organic food is increasing  Sales increased 20%/year in Canada and the U.S. from Expanded by a factor of 40 in Europe  Amount of land for organic farming is increasing 10-35%/year in the U.S. and Canada In 2005 the U.S. had 1.7 million acres of organic cropland and 2.3 million acres of organic pastureland

The benefits of organic farming  For farmers: Lower input costs, enhanced income from higher- value products, reduced chemical costs and pollution Obstacles include the risks and costs of switching to new farming methods and less market infrastructure  For consumers: Concern about pesticide’s health risks A desire to improve environmental quality Obstacles include the added expense and less aesthetically appealing appearance of the product

The U.S. doesn’t financially support organic farmers  In 1993, the European Union adopted a policy to support farmers financially during conversion to organic farming  The U.S. offers no such support Organic production lags in the U.S. Farmers can’t switch, because they can’t afford the temporary loss of income In the long run, organic farming is more profitable

Organic agriculture succeeds in cities  Community gardens = areas where residents can grow their own food  In Cuba, over 30,000 people work in Havana’s gardens, which cover 30% of the city’s land Record yields for 10 crops in

Locally supported agriculture is growing  In developed nations, farmers and consumers are supporting local small-scale agriculture Fresh, local produce in season  Community-supported agriculture = consumers pay farmers in advance for a share of their yield Consumers get fresh food Farmers get a guaranteed income

Food Production Has Increased Dramatically  Three systems produce most of our food Croplands: 77% Rangelands, pastures, and feedlots: 16% Aquaculture: 7%  Importance of wheat, rice, and corn  Tremendous increase in global food production

Industrialized Crop Production Relies on High-Input Monocultures  Industrialized agriculture, high-input agriculture Goal is to steadily increase crop yield Plantation agriculture: cash crops Increased use of greenhouses to raise crops

A Closer Look at Industrialized Crop Production  Green Revolution: increase crop yields Monocultures of high-yield key crops E.g., rice, wheat, and corn Use large amounts of fertilizers, pesticides, and water Multiple cropping  Second Green Revolution  World grain has tripled in production

Food and Biofuel Production Systems Have Caused Major Biodiversity Losses  Biodiversity threatened when Forest and grasslands are replaced with croplands  Agrobiodiversity threatened when Human-engineered monocultures are used  Importance of seed banks Newest: underground vault in the Norwegian Arctic

We Use Pesticides to Try to Control Pest Populations (2)  First-generation pesticides  Second-generation pesticides Paul Muller: DDT Benefits versus harm  Broad-spectrum agents  Persistence

Modern Synthetic Pesticides Have Several Advantages  Save human lives  Increases food supplies and profits for farmers  Work quickly  Health risks are very low relative to their benefits  New pest control methods: safer and more effective

Modern Synthetic Pesticides Have Several Disadvantages (1)  Accelerate the development of genetic resistance to pesticides by pest organisms  Expensive for farmers  Some insecticides kill natural predators and parasites that help control the pest population  Pollution in the environment  Some harm wildlife  Some are human health hazards

Modern Synthetic Pesticides Have Several Disadvantages (2)  David Pimentel: Pesticide use has not reduced U.S. crop loss to pests Loss of crops is about 31%, even with 33-fold increase in pesticide use High environmental, health, and social costs with use Use alternative pest management practices  Pesticide industry refutes these findings

Laws and Treaties Can Help to Protect Us from the Harmful Effects of Pesticides  U.S. federal agencies EPA USDA FDA  Effects of active and inactive pesticide ingredients are poorly documented  Circle of poison, boomerang effect

Reduce Soil Erosion  Soil conservation, some methods Terracing Contour planting Strip cropping with cover crop Alley cropping, agroforestry Windbreaks or shelterbeds Conservation-tillage farming No-till Minimum tillage  Identify erosion hotspots

Buy Locally Grown Food  Supports local economies  Reduces environmental impact on food production  Community-supported agriculture