“Sustainable Agriculture: Looking

at Soils, Seeds & Nutrition”

Global Science, Ch. 6p. 216 - 266

Section 6.1 - Introduction to soils

• Terrestrial life is supported by soil• Good soil = Healthy Ecosystem = Healthy Living

• No soil when Earth was formed• Primitive plants began soil formation processes

• Growing plants also contributed– Roots– Organic matter

• Soil - mixture of minerals, organic matter, water and air with a definite structure and composition and forms the surface of the land

Section 6.1 - Background Information

• Horizons - layers of soil• Three major horizons

– Top soil– Subsoil– Parent material

•More or less layers may be present•Layers make up the soil profile

Soil profile - succession of distinctive soil layers from the

surface down to the unchanged parent material• O-horizon: top

layer; organic matter

• A-horizon: top soil; economically valuable; 1” to 24”; “zone of leaching”

• B-horizon: subsoil; “zone of accumulation”; poor organic content

• C-horizon: not part of the soil; parent material; no distinct lower limit

• Decomposers break down organic matter to release sulfates, nitrates, and phosphates

• Rate of soil formation depends on “parent” material, region, climate and surface features– Hard parent material = 100’s of years– Soft parent material = 20 to 30 years

• Soil color can serve as an indicator of the quality of soil

• Upper Layer - lots of life– Maintains porosity

• Mineral particles are classified into three main groups– Large coarse = sand– Somewhat finer = silt– Extremely fine = clay

• Relative samples of particles determines soil texture

34%

34%

32%

• Suitability for agriculture depends on both texture and structure– Most productive have these characteristics

• Crumbly texture• Well aerated• Retains water

• Fertile soil must be able to supply the complete set of nutrients to the plant

• Chemical analysis determines what essential nutrients are present or deficient and how much fertilizer to add– Essential nutrients: N, P, S, K, Ca, Mg, C, H, and O

– Minerals released through weathering– Application of limestone, commercial fertilizer, manure

• Plants require large amounts of these elements: N, P, K– Reserves are depleted quickly, measures can be taken to replace

• N - stimulates above ground growth, green color, determines plants ability to use other nutrients; replaced by growing legumes, add organic matter, commercial fertilizer

• P - abundant in fruits of plants and seeds, root hairs (rapid uptake of water nutrients), energy transferring processes; replaced by manure and commercial fertilizers

• K (potash) - vigor and vitality of the plant, healthy root, synthesis of starch and translocation of carbohydrates; replaced with commercial fertilizers

• Ca deficiency rarely a problem due to placing lime on soil, to increase pH; Mg all soils have Mg sources, deficiency corrected with pulverized dolomite or limestone; S found in organic matter

• Mn, Fe, B, Cu, Zn, Mo, and Cl - trace amounts required; essential to animal health and maintenance of health in humans

Macronutrients & Micronutrients

• pH - refers to the degree of acidity or alkalinity (basicity) of a substance; ranges from 0 - 14– Below 7 is acidic– Above 7 is alkaline– Common soils range from 3 - 10

Section 6.1 - Natural Selection

• Process by which the organisms that survive have genetic characteristics that are naturally selected for in the environment– Certain characteristics increase survival; increase in reproductive success

– Survival of one form over another leads to changes in proportions of certain genes within the population

Section 6.2 - Non-Human Organisms & Agriculture

• Majority of organisms survive on products produced through agriculture; either directly or indirectly

• Spoilage - breakdown by fungi, bacteria and other decomposers; competition for food

• Most serious and widespread threat to human food supply is insects– Estimated 30,000,000 (million) species– Outweigh humans 12:1 (pounds)

Section 6.3 - Natural Selection, Pests, and the Food Supply

• What do you think is the best way to get rid of insects and protect our food supply?

Section 6.3 - Natural Selection, Pests, and the Food Supply

• What do you think is the best way to get rid of insects and protect our food supply?

• Insecticides• Integrated Pest Management

• Ecosystem - “marvelous” dynamic thing, energy flows through and powers the system, can be disturbed and damaged; ecosystems are linked to other ecosystems

Section 6.4 - Plant Nutrition

• Food chain is made of three levels– Producers– Consumers– Decomposers

• Producer needs:– Sunlight, water, oxygen, carbon dioxide, minerals

– Photosynthesis– Respiration

• Heat

– Essential minerals (13): N, K, Ca, P, Mg, S, Mn, B, Fe, Zn, Cu, Mo, Cl

Section 6.5 - Animal Nutrition

• Nutritional needs of animals include: – Water– Minerals– Proteins– Fats– Oxygen– Vitamins– minerals

• Obtain energy either directly or indirectly from green plants– Breaks down energy rich molecules from photosynthesis to less energetic molecules animals use as building blocks

• Metabolism - chemical reactions that take place inside the body; nutrition and uptake of minerals is necessary for metabolism

• Water - regulates body temperature, transports nutrients, carries waste, participates in metabolic reactions– Adult human body is 65% water

– How much water are you?

• Oxygen - required for respiration

• BOTH PLANTS AND ANIMALS CARRY OUT RESPIRATION

• Essential mineral elements - involved in the function of nerves and muscles, formation of bones and teeth, activation of enzymes, transportation of O (Fe)

• Vitamins - organic molecules necessary for higher organisms to perform specific biological functions; vitamins and enzymes often work together– Vitamin K - blood clotting

• Proteins - broken down into amino acids, reassembled to form different proteins, organ structure, enzymes, antibodies, hormones, metabolically active compounds

• Carbohydrates - energy; adequate supply of carbohydrates prevents the breakdown of proteins for energy– “protein sparing”

• Fats - maintains cell membrane structure and function, building blocks of hormones, concentrated source of energy, carry some vitamins, provide insulation and protection for some organs

• Proper nutrition is important for growing healthy plants and animals; excess amounts is converted into fat

• At the time the book was published the world was making enough food to feed all of its citizens

• Possible ways of increasing/expanding our food production and feeding more people, but some practices are harmful– Farming marginal land– Reliance on new high-yield hybrids

• Hybrids - mix of plants that does not occur in nature• Most profitable to plant 1000’s of acres of the same crop

• Decrease genetic diversity• Very risky

– Lack of germplasm (hereditary material necessary to resist pests or fight environmental stresses

Section 6.7 - Seed Banks & Insectaries

• Genetic diversity of plants must be preserved to recover from potential epidemics and natural disasters– Large expanses of various ecosystems must be preserved

– Seed banks

• International Board of Plant Genetic Resources (IBPGR)– Established in 1974– Create and coordinate a worldwide germplasm resource conservation and centers

– Funded by World Bank, United Nations Development Program

– Future needs - plants will be needed to survive a variety of different climate changes; storehouse of genetic material is ourr best chance for survival;

– Researchers must be able to draw on the numerous plant and animals species that re quickly diminishing

• Insectaries - place where beneficial insects are raised for use in controlling certain plant species and insect pests

– Biological pest control• Considered to be a safe practice

• Exotic species must be strictly quarantined before made available for general release

• Approximately 25 government funded insectaries in the United States

Section 6.8 - Plant Biotechnology and Agriculture

• For centuries farmers have used a variety of techniques to improve the quality of their crops/livestock– Selective breeding

• Called hybridization in plants• Still used today

– Plant Biotechnology • Transfer of very specific genes from one plant to another

• Only adds beneficial traits

Section 6.9 - The Concept of Carrying Capacity (K)

• Carrying capacity – Maximum number of given organisms an ecosystem can support

– Number of people the Earth can support is tied to the standard of living

Section 6.10 - Various Perspectives on Carrying Capacity

- Our Population Should Be Kept Well Below 10 Billion

- Earth Can Support Many More Vegetarians Than Meat- Eaters

- Technology and Human Ingenuity Will Keep Us Fed

Our Population Should Be Kept Well Below 10 Billion

• Estimated that food production will likely ever grow to more than 9 times what it is now

• Carrying capacity of Earth is well over 30 billion by 2075– Most of whom will be near starvation

• Even if population levels off near 10 billion by 2050 there will need to be extensive management of resources to have any comfort

• For everyone to have enough food and environmental quality to be maintained the population needs to stay below 10 billion

Earth Can Support Many More Vegetarians Than Meat-Eaters

• Belief that Earth’s carrying capacity could be extended if humans quit raising animals for food and use the land to grow grain for human consumption (2nd Law of Thermodynamics)– Average steer: 16 lbs. grain/soy = 1 lb. of meat on the plate

• Eating “lower on the food chain” allows Earth to support more people

• Same amount of food material feeds 4 times as many people in India and China than it does in the United States and France– 210 million Americans = 1.5 billion Chinese

Technology and Human Ingenuity Will Keep Us Fed

• Today farmers are producing 5 times as much food product as they did in the 1920’s

• Enough food produced to ALL Americans plus 100 million people abroad

• Emerging technologies may enable farmers to further expand the amount of food they produce

• High-Yield Farming - collection of techniques designed to maximize the amount of food produced per acre of farmland– Sustainable over the long term must attend to water conservation and prudent pesticide use

Section 6.11 - So How Many People Can the World Support?

Primary Thinker Estimate of Maximum Population Key Ideas Behind Calculations E.G. Ravenstein; England 1891 5,994,000,000 (almost 6 billion) Potential of different types of land

to support a population of a given size

Albert Penck; Germany 1924 15 billion possible, but 7.689 is more probable

Number of people on Earth = production area X production per unit area divided by the average nutritional requirements of 1 person

C.T. De Wit, Netherlands 1967 1,000 billion (if space is not considered) 146 billion (750 sq. meters per person for all space needs)

Rate photosynthesis is the limiting factor to determining how many people the Earth can support

H.R. Hulett, United States 1970 Less than 1 billion* Used the average U.S. citizen’s consumption of food and other raw materials to determine the optimum size for the population based on this rate of resource consumption

Roger Ravelle, United States 1967 40 billion people Food limits population size, therefore calculating arable land and potential crop yield will determine population size

Colin Clark, Australia 1967 157 billion people with a subsistence diet and minimal wood use, 47 billion with a US diet and wood use

Based on the amount of land available to raise food and wood

Food & Agricultural Organization, United Nations 1983

33 billion in Africa, Asia, South America and Central America

Based on the physical potential of lands in developing world to grow enough food to support minimum nutritional requirements

Robert Kates, United States 1991 5.9 billion people on a basic vegetarian diet 3.9 billion people on an 85% vegetarian, 15% animal products 2.9 billion on a 75% vegetarian diet, 25% animal products

Based on determining how many people can live on the known primary food supplies in the world (similar to Penck’s formula)

Table 6.52 - Summary of Eight Estimations of Maximum Population