SAFS 405 Final Exam
What are some examples of cultural pest and disease management techniques? (note that you should understand how each of these works!)
- crop rotation - sanitation of planting materials - barriers; e.g. fences, rowcovers. - perimeter trap crops - using deterrents to pests - physical removal of pests
Eisler suggests several ways that we could enhance the sustainability of our livestock production systems worldwide. Give some examples.
- feed less human food to livestock, focus instead on waste products (such as leftovers from food processing like sugar beets, orange juice), multi-use plants (for example, plants that produce human food and the rest of the plant can be used for livestock feed), and pasture. - raise regionally appropriate animals (breeds adapted to the diet, stress, and management conditions they will face in a particular area) - track energy use in livestock systems we can capture as much of it as possible - keep animals healthy (reduce stress in livestock raising systems so that we get fewer losses and can reduce antibiotic use) - eat quality, not quantity - the US per capita consumption of meat is among the highest in the world, Eisler argues that we (and the planet) would be better served by eating less meat (reducing demand) that is produced in more sustainable ways.
What are some different ways we can learn about a soil's physical, chemical or biological characteristics?
-A penetrometer tells us how compacted a soil is. -Texture analysis (in the lab, or by feel) -A standard chemical soil test run by a lab (to determine plant-available nutrients, organic matter content, and CEC). -Various tests of aggregate stability (like the slake test from the video) tell us whether or not there is favorable secondary structure (or aggregation) of soil particles. -We can evaluate the elements found in plant tissues that are being grown in the soil; this gives us an indication of whether soils have sufficient plant nutrients. -Different assays for soil biological activity (like the Solvita test, or bioassays) give an indication of how much microbial activity is present in the soil.
We spent some time discussing the results from the paper by Smith-Spangler et al (2012). This paper reported the results of a meta-analysis of several hundred studies comparing organic vs. conventional foods. Based on what the researchers found, do there appear to be differences between organic and conventional foods in the following categories? -risk of detecting any pesticide residues in fruits, vegetables & grains -risk of detecting E coli in fruits, vegetables & grains -risk of detecting other enteric pathogens in meat and egg products -risk of detecting antibiotic-resistant bacteria in meats -risk of detecting naturally occurring mycotoxins such as DON and OTA -risk of detecting heavy metals like cadmium, lead, arsenic and others
-risk of detecting any pesticide residues in fruits, vegetables & grains: organic foods tend to have lower risk -risk of detecting E coli in fruits, vegetables & grains: there is no difference -risk of detecting other enteric pathogens in meat and egg products: there is no difference-risk of detecting antibiotic -resistant bacteria in meats: there is no difference -risk of detecting naturally occurring mycotoxins such as DON and OTA: organic foods appear to have a slightly lower risk for DON, but no difference for ochratoxin A -risk of detecting heavy metals like cadmium, lead, arsenic and others: there is no difference
Why is it important to have many (abundant) diverse types of organisms living in the soil?
1) the more species are present in an agroecosystem, the less likely crop damage is to occur 2) different populations keep one another in check through predator-prey balance. 3) Different types of organisms perform different ecosystem functions... e.g. some are decomposers, some are predators, some are herbivores, etc. The more ecosystem functions that are filled, the more efficiently energy is used in that system. Another way to think about it is that fewer resources are wasted.
List at least three functions that soils perform in agriculture.
1. Anchors plants 2. Serves as reservoir for nutrients 3. Allows for air and water exchange (between plant and environment)
The industrial revolution had a major impact on agriculture. Give three examples of industrial revolution developments and for each, explain how it impacted agriculture and food production.
1. Farm mechanization - replaced animals (and therefore made manure use impractical), required capital investment by farmers, increased the amount of production possible on a given amount of land with a given amount of labor 2. Transportation - enabled food production to take place a lot further away from population centers 3. Manufacturing Technology - enabled mass production of farm equipment (tractors, and more specialized things that tractors pull), farm chemicals (synthetic fertilizers and pesticides), etc.
Agricultural practices have the potential to negatively impact natural resources, and therefore reduce the ability of ecosystems to provide the services they typically provide. Give some examples of how agricultural activities can harm natural resources.
1. Soil degradation - soil is lost through erosion (wind and water) and loss of nutrients through overuse (mining) in some parts of the world. 2. Water pollution - Silt & Sediment contaminate surface waters, destroying habitats for aquatic organisms. Fertilizers contaminate water with nutrients, which can cause blooms of growth oforganisms and then oxygen-starved conditions. Pesticides, Pathogens, and Heavy Metals can contaminate surface and ground waters. Overdrawing ground water can result in salinization of water near coastal areas. 3. Genetic Diversity - Widespread use of monoculture increases the vulnerability of specific fields to epidemics (insects, diseases etc.); Genetic Diversity can be lost by wide adoption of a few high-performing varieties; this means that the population of crops grown are less able to respond to changes in their environment
When was the Organic Food Production Act passed? When were the National Standards first implemented?
1990; 2002
What are the recent trends in production and consumption of animal products (meat and milk) worldwide?
30% of the ice-free land worldwide is used for livestock production systems, and this makes up nearly 80% of our agricultural land. Worldwide, livestock production AND consumption has increased dramatically in the last 30-60 years. We see more dramatic increases in the developing world than in developed countries. Livestock production has also become more efficient, with carcass weight for meat animals like pigs, cattle, and chickens increasing steadily during this time.
Aside from making an agricultural ecosystem more resilient to disturbances, what are some other reasons that biodiversity is helpful in agriculture?
A diverse collection of organisms plays several roles in agriculture, including: - Nutrient cycling (recycling organic matter - think the nitrogen cycle) - Detoxifying or breaking down contaminants - Biological pest controlPollination
What is a "green manure" cover crop? What characteristics should a good green manure crop have?
A green manure crop is one that is grown for the purpose of incorporating it into the soil to increase the soil organic matter. It is being used as a soil amendment. A good green manure crop would have a lot of biomass (e.g be a BIG plant), fix nitrogen (e.g. be a legume), and would grow quickly to suppress weeds.
Define phototropism
A plant's response to light
Again focusing on the paper by Smith-Spangler et al (2012), are organic foods more nutritious than conventional foods?
Across the many studies evaluating several types of nutrients, only two aspects of nutrition were significantly higher in organic than conventional produce: phosphorus and total phenols. The many others evaluated (vitamin A, vitamin C, etc.) did not show a consistent and significant difference according to production system.
Give at least two advantages and two disadvantages of using classical biological control to manage insects.
Advantages: Self-sustaining and permanent if successful because the predator-prey relationship will keep both populations in check, it is not expensive for farmers, it is environmentally friendly because it's a chemical-free approach. Disadvantages: It might not work because the organism might not thrive in this environment, It takes a very long time, Introducing an organism might have unintended consequences
What is the difference between annual, biennial, and perennial crop plants?
Annual plants germinate, grow, flower, and reproduce once in a single year. Biennial plants take two years to accomplish this same life cycle. Perennials live and reproduce again and again over many years.
Define aquaculture.
Aquaculture could be defined as the farming of marine and freshwater plants and animals for human consumption (food), recreation, baitfish, or restocking. Aquaculture is a form of agriculture using water as the medium, instead of soil.
Define aquaponics, and describe basic functioning of an aquaponics system.
Aquaponics is the combination of aquaculture (raising aquatic animals) with hydroponics (raising plants in nutrient-enriched water). The idea with these systems is that with fish feed as the primary input, fish waste in the water is converted into plant-available forms of nutrients, and plants harvest those nutrients from the water, simultaneously cleansing the water. The goal is to produce two types of food (typically fish and plants) at the same time.
List and describe at least five factors that affect the nutrient content of fruits and vegetables.
BEFORE harvest, how food is produced can affect nutrient content: •Variety choice. Some varieties have much higher levels of vitamins and minerals than others. •Soil nutrient status. Chronically depleted soils can produce crops with lower levels of certain minerals than very fertile soils. Similarly, produce grown in soils with very high levels of certain minerals may have higher levels of those minerals. •Maturity at harvest. Nutrient content changes as the plant goes through its' life cycle; harvesting too early or too late can result in a less nutritious product. •Diet. Ruminant livestock (cows, sheep, etc.) that are fed grass (as opposed to grain) produce higher levels of Conjugated Linoleic Acids, which have antioxidant activity. •Stresses to the plant. Many secondary metabolites produced by the plant have antioxidant activity, and these are produced in higher amounts when plants are exposed to various stresses (UV light, drought, etc.). AFTER harvest, how you handle your fruits & vegetables can impact nutrient content: •Freshness and storage conditions. While minerals are quite stable, Vitamins like A and C are quite unstable when exposed to heat, light, and oxygen.
Why is biodiversity useful in an agricultural ecosystem?
Biodiversity in an ecosystem makes that ecosystem better able to cope with change - the existing resources in the ecosystem are used more efficiently, more ecosystem functions and niches are being filled, and the ecosystem is more resilient to disturbances (physical, biological, environmental, chemical, etc.)
What is Cation Exchange Capacity (CEC) of a soil? Is it better to have soil with a high or a low CEC?
CEC refers to the ability of a soil to adsorb (or hold onto) cations in the soil. Cations are positively charged ions. Many plant nutrients, such as Calcium (Ca), Potassium (K), Magnesium (Mg), and ammonium (NH4), are present in the soil as cations. A high CEC is better because it means more ability to hold onto nutrients.
What is the difference between a cash crop and a cover crop? What are some reasons that a farmer might choose to plant a cover crop? Are there any drawbacks to cover cropping?
Cash crops are planted in order to be harvested (grains, vegetables, fruits, hay, etc), whereas cover crops are planted for other purposes, primarily to build the soil. Reasons to plant cover crops are primarily to prevent soil erosion, to "catch" nutrients and prevent leaching, and to build soil fertility - but they can also be used for other purposes such as biofumigation. Drawbacks are that cover cropping adds expense (seeds, management time), and that when cover cropping, the land cannot be used for cash crops. If not managed properly (tilled before setting seeds), the cover crop can become a weed or can increase weed problems.
What is compost?
Compost is a biologically stable material that results from decomposition of organic residues
When building a compost pile, why would someone need to know the carbon to nitrogen (C:N) ratio of the starting materials?
Composting (especially hot composting) relies on thermophilic (heat-loving) bacteria. Bacteria require their "diet" to be roughly 25-30:1 C:N. If there is excess Carbon, the bacteria will not be able to completely break down the raw ingredients. If there is excess Nitrogen, the excess Nitrogen will be volatilized and released as ammonia (leading to a stinky compost pile).
Why would a farmer decide to compost her manure before she used it in her garden? Are there any drawbacks to doing this?
Composting kills plant pathogens, animal pathogens, and weed seeds that are found in manures. The farmer could use composted manure right away on her organic garden without worrying about food safety issues that could be a problem with raw manure. Composting also reduces odor and improves the texture of the manure. HOWEVER, drawbacks are that much of the nitrogen found in manure is lost during composting, and the process of composting can be quite time-consuming.
What are some of the consequences of having more physical distance between producers (farmers) and consumers? Are there any advantages?
Consequences: food travels farther, longer time between harvest and consumption, consumer is less aware of production issues (seasonality, crop losses, effects of weather, labor requirements), lower prices to farmers but higher prices for buyers Advantages: increased availability of produce out of season, permits specialization and consolidation which can increase production efficiency, making food cheaper for the consumer.
List and describe several strategies that farmers might use to conserve their soil resources; e.g. prevent erosion.
Contour planting - crops are planted in strips perpendicular to the slope on a field Terracing - crops are planted in narrow level areas that are created on very steep hillsides Perennial crops - do not require tillage, so therefore hold the soil in place better than those which require that the soil be tilled up every year.
Crop rotation provides some of the benefits of a polyculture system as well as some of the benefits of a monoculture system. Explain what crop rotation is, and list at least 3 reasons that crop rotation is a good idea.
Crop rotation is a planned system of growing different crops in succession on the same piece of land. Rotation provides some of the benefits of polycultures: increased biodiversity, yield stability and more efficient and complete use of resources, but usually only over time - not within a growing season. (Note - It doesn't give much protection against crop failure within a given year!). Within a growing season, a crop in rotation can be grown as a monoculture. The primary benefit is ease of management because of uniform crop needs, harvest time, and growth habit.
What are some problems with certain types of aquaculture systems? Give an example or explain each problem you describe.
Environmental degradation -shrimp ponds constructed at the interface between ocean and mangrove swamps destroys critical habitat for many species. Crowded fish cages - when there are too many fish in too many closely spaced fish cages, water does not flow through to refresh, leading to contaminated water (nitrates and other waste products, etc.) where the fish are growing. Antibiotic use - in crowded conditions, disease is more likely. Where it is allowed, antibiotics are sometimes used preventatively.
Fish used as food can be categorized as filter feeders, herbivores, omnivores, and carnivores. Define these, and explain the implications for aquaculture of these species.
Filter feeders eat phytoplankton, Herbivores eat plants, Omnivores eat plants as well as other smaller animals, and carnivores eat other animals/fish. Filter feeders: oysters, scallops, mussels Herbivores: sea urchins Omnivores: catfish, tilapia Carnivores: shrimp, cod, cobia, halibut, salmon The higher up the food chain, the higher the protein requirements for feeding and the more fish meal is needed to grow that organism in an aquaculture system. Since energy is lost at the transition between each trophic level, producing top carnivores takes a LOT more energy than producing species that are lower on the food chain.
If we think of the soil as a pool of available nutrients for plant growth, what are the processes by which we add nutrients to, and subtract nutrients from, the pool?
Gains: fertilizers, nutrient fixation, microbial decomposition, weatheringLosses: plant uptake, volatilization, erosion, nutrient fixation, and leaching
How would you describe a soil that is "healthy" from a biological, physical, and chemical perspective?
Healthy soils are ones with: -abundant and diverse living organisms (biologically healthy) -plenty of nutrients required by plants (chemically healthy) -well-aerated with plenty of pores (physically healthy)
What rules do certified organic farmers have to follow if they use 'raw' animal manures? What's the reasoning behind these rules?
If they use raw manure, they can only use it on non-edible or perennial crops, or at least 60 days before harvest on edible crops like vegetables. Composted manure can be used at any time. The purpose is to reduce the risk of pathogens like E.coli in the harvested food. They also have to provide a plan for how they will apply and use manure in a way that doesn't contaminate waters with bacteria or nitrates.
Explain the difference between an overlap planting of two crops and planting a mixture of the same two crops. What are the advantages of each?
In an overlap planting, the two crops would overlap for some part of their life cycles. In a mixture, the two crops would be planted together, and would overlap for their entire life cycles. Mixtures increase crop biodiversity throughout the entire growing season, conserve water and nutrient resources. The two crops might complement one another (increasing total production season or increasing total yields), or might be antagonistic or compete for resources. Overlap planting minimizes some of the competition that can occur in mixtures, and therefore often provides better yields.
What do the organic regulations say about livestock production?
In organic production, all livestock must have access to the outdoors. All feeds must be certified organic. For ruminants: - must graze during the pasture season (at least 120 days), and get at least 30% dry matter from pasture during this time. - finish feeding period (for meat animals) where grain is fed to maximize meat quality cannot exceed 120 days.
Define 'integrated pest management'. What are some key practices that are part of integrated pest management?
Integrated pest management is the use of different techniques in combination to manage pests, with an emphasis on methods that are least harmful to the environment and most specific to the particular pest. TO do this, growers need to understand how each pest works; e.g. it's life cycle and how/when/where it causes damage. Key practices associated with Integrated Pest Management include: - avoiding conditions that favor pests/diseases - using cultural methods to control pests - monitoring regularly for pests - relying on natural enemies to control pests - use pesticides as a last resort (and try to use the most specific pesticide possible).
Classical biological control
Intentional introduction of natural enemies from native range to control an exotic pest
How does 'finished' compost different from the feedstocks (aka the starting materials)?
It's already decomposed, nutrients are in a more stable (and less available) form, pathogens & weed seeds are killed, it has a finer texture, and smells and weighs less.
Are crop farms, livestock farms, or integrated (crop plus livestock) farms more likely to end up accumulating nutrients because nutrient IMPORTS exceed nutrient EXPORTS?
Livestock farms tend to accumulate nutrients because a large amount of nutrients end up staying on the farm as manure. Crop farms tend to have a nutrient deficit because most nutrients are exported off the farm as crops. Integrated farms may be more likely to be able to balance nutrient inputs and output.
What are macronutrients? How do they differ from micronutrients? Name the three primary macronutrients.
Macronutrients and micronutrients are both required for plant growth, but macronutrients are needed in large quantities by the plant. The primary macronutrients are: Nitrogen, Potassium and Phosphorus. Secondary macronutrients are: Calcium, Magnesium, and Sulfur. Micronutrients include: boron, chlorine, copper, iron, manganese, molybdenum, and zinc. Some (but not all plants) require nickel, cobalt, silicon, sodium and selenium. Note that there are three other essential elements that plants get from air and water... (C, H and O).
Where in the soil profile are most of the soil biota found?
Most are found in the top 10-15 cm of soil, or the top 4-6 inches.
What does the word "organic" mean, chemically speaking? How does this relate to "organic" agriculture?
Organic = carbon-containing. All forms of plant and animal life are carbon-based, so as they decompose they are referred to as 'organic matter'. The term "organic agriculture" originally was used to describe agricultural systems that rely primarily on decomposing plants and animals, or organic matter, as a source of fertility in the soil and for the next crop.
The 'Certified Organic' label has been described as focusing on the process rather than the product. Briefly explain what that means.
Organic certification focuses on the processes that farmers and food manufacturers use to grow and produce foods, rather than on specific qualities of the foods themselves. Foods aren't tested for any particular attribute - such as absence of pesticide residues, traces of genes from GM crops, or microbial contamination. The label simply tells the consumer something about the practices used to produce the food.
What is the difference between organic and sustainable agriculture?
Organic is a federally regulated term that means something very specific. One can be certified organic in the short term. Sustainable agriculture is one that can continue indefinitely while remaining productive. Most agree that it entails several dimensions: economic, environmental and social viability. Sustainability is hard (if not impossible) to demonstrate in the short term, but it is something one can strive for.
What is Soil Organic Matter, and why is it considered important and beneficial?
Organic matter is the sum total of the dead, decomposing, and completely decomposed organisms in the soil. Decomposing OM provides food for living soil organisms. As it is broken down, it produces sticky substances which promote aggregation and good soil structure, which in turn helps water infiltration and water-holding capacity. Stable decomposed organic matter particles have high cation exchange capacity (CEC), which means they are hold plant-available nutrients well.
We spoke about the long-term research project that several groups have been working on; development of perennial wheat. What would the advantages be of having a perennial wheat rather than the annual wheat we currently grow?
Perennial wheat would not require annual tillage before planting; which would reduce soil erosion. The deep root system of a perennial grass would be better able to access deep water and nutrients, and might be more resistant to stresses like drought. It would also hold the soil better than the puny root system of annual winter wheat. Another advantage would be that farmers would not have to purchase or save seeds, assuming that the perennial wheat would live for several years.
Plants and several soil organisms are considered primary producers, or photoautotrophic. Explain what this means, and where these organisms fit in the food web.
Photoautotrophic organisms are ones that photosynthesize, or use solar energy (plus water and carbon dioxide) to create carbohydrates. Because these organisms don't feed on other organisms, they are the foundation of the food web; all other organisms ultimately depend on them (or upon things that feed on them) as food.
Name and briefly describe the process by which plants harvest energy from the sun. List the inputs and outputs of this process, and describe when and where it occurs within the plant.
Photosynthesis occurs in the chloroplasts within plant leaf cells. Inputs are water, carbon dioxide and light energy, and outputs are glucose, water, and oxygen.
What does the plant do with the glucose that is produced during photosynthesis?
Plants use some of the glucose that is produced to fuel cellular processes. It is used during cellular respiration. During respiration, in the presence of Oxygen, Glucose is broken down into carbon dioxide and water, releasing energy in the form of ATP.
What could be some positive and negative consequences of having a federally-regulated organic label? (list at least 3 of each). Does this favor smaller or larger farmers? How could this effect the consumer?
Positive: consistent meaning, interstate trade of organic produce is easier, increased value of organic, increases overall organic acreage Negative: interstate trade of organic produce is easier, makes it easier for growers driven by profits rather than philosophy to enter the marketplace, many of the ideals described in regional labels are not included in the federal standard
Farmers and gardeners usually till soil to prepare it before planting. What are the pros and cons of doing this?
Pros: - makes the soil fluffy and soft, good for planting and seed germinating - incorporates organic matter into the topsoil Cons: - Can result in compaction of the soil (especially if done when soil is wet), and the creating of 'plow pans'. Crop roots don't grow well in compacted soil. - Tillage can break down soil structure at the soil surface, leading to crusting and erosion. - Incorporating oxygen into the soil can increase the rate of decomposition of organic matter within the soil.
Give at least two well-founded reasons why organically grown crops might be MORE nutritious than their conventionally grown counterparts, AND at least two well-founded reasons why there might be no difference.
Reasons Organic might be more "nutritious": •More attention might be paid to building soil nutrient levels; higher soil nutrient levels might be taken up into crops. •In organic dairy and meat production, ruminant animals are required to have a portion of their diet met by grazing on grasses (which would increase CLA levels). This is not a requirement for conventional systems. •Organically grown crops may experiences more stresses, and therefor may produce more defense-related compounds which have antioxidant effects. Reasons that there might be no difference: •Conventional and organic farms BOTH are careful to provide enough nutrients in fertilizers to meet crop needs, and healthy crops contain balanced amounts of macro and micro-nutrients they need. •Things like crop variety, weather, and freshness are likely to impact nutrient levels as much as more than the source of plant nutrients/type of fertilizer. •There are both conventional AND organic livestock operations that use grass or forages as their primary feeds.
The soil bacterium Rhizobium is a very important soil microorganism in agricultural soils. What does it do, and why is it so important?
Rhizobium is a soil bacterium that infects the roots of Legume plants in a symbiotic relationship. Infected roots make nodules around the bacteria. Within the nodules, the bacteria convert atmospheric nitrogen (N2 gas) into nitrate that the plants can use, and they use as food the carbohydrates produced by plants. Without Rhizobium, legume plants would not fix nitrogen.
What are ruminant animals? List at least three species of ruminant animals.
Ruminant animals have a four-chambered stomach, which allows them to utilize energy from cellulose by breaking it down via microbial fermentation in the rumen. This enables them to consume high-fiber foods that non-ruminants cannot, such as grasses and forages.Ruminants include: cattle, goats, sheep, buffalo, camels, llamas, reindeer, deer and yak. Non-ruminants include: poultry, pigs, rabbits, horses and humans.
What are the three fundamental soil particles, and what is the key feature that differentiates them?
Sand, silt, and clay. The major difference is particle size! Particles of sand are larger than those of silt, which are larger than those of clay.
What happens to chemical residues on materials that are composted?
Several things happen. The fate varies, depending on which chemical you are talking about. Some pesticides are mineralized to produce inorganic compounds. Others are partially degraded to form other, different, compounds. Some are bound tightly to (or complexed with) humus particles. Yet others are lost, through volatilization, leaching, etc. A few (such as the aminopyralid example we discussed) don't break down quickly and are concentrated during composting because they are persistent in the environment.
What is sewage sludge, and why is its use as an agricultural amendment considered controversial (and not allowed in organic systems)?
Sewage sludge is the untreated residue that's left over after processing human waste in a sewage treatment facility. While it is normally processed to kill any human pathogens, sewage sludge contains all of the things that go down household and industrial sewage systems. This includes some items that can be concentrated if applied to agricultural lands: pharmaceuticals, heavy metals, radioisotopes, etc.
If a farmer normally uses her own cow manure, but then sells her cows and starts buying manure from her neighbor, can she use it the same way? Why or why not?
She might be able to - but she would need to know whether it's from the same kind of animal (cow vs. poultry vs. hog?) and whether the final product has the same percentages of different nutrients as her cow manure did. Animal manures may be very different according to diet, type of manure, amount of bedding mixed in, etc.
What is soil texture? What is the difference between soil texture and soil structure?
Soil texture is an innate property of a soil, determined by the proportion of sand, silt and clay particles. Soil structure refers to the arrangement of the fundamental soil particles into larger units, and is affected by mechanical and biological activities in the soil. Agricultural practices, such as tillage and anything that causes compaction, affect structure!
Are hormones and antibiotics used in livestock production? Explain.
Some hormones are used in livestock production beef, lamb, and dairy cattle production. None are approved for poultry or hogs. Antibiotics can be used two ways in livestock production: clinically(to control diseases) and non-clinically (to improve growth). When they are used, withdrawal periods must be followed before meat and milk enter the food supply. Antibiotics are routinely tested in milk and meat, to ensure that levels are below legal limits, or tolerances.
Why are microbes an important part of the nitrogen cycle? List at least three functions microbes perform in the nitrogen cycle.
Some microbes mineralize N (convert it from organic to inorganic forms) as they decompose organisms, by ammonification and nitrification. Some microbes fix N (convert it from N2 gas to inorganic nitrogen). As microbes use N themselves, they immobilize N (convert in into an organic form).
Define the following terms, which describe interactions between organisms in an ecosystem: symbiosis or mutualism, competition, antagonism, and parasitism.
Symbiosis/Mutualism - a mutually beneficial relationship Competition - demand by at least 2 organisms for limited resources Antagonism - Inhibition of or interference of a substance or organism by another Parasitism - one organism receives benefits from another by directly causing damage to it.
In the national organic standards, what is the "national list"? Give an example of an item that appears on this list and explain whether it can or cannot be used on organic farms.
The National List appears in the organic standards. In general, all synthetic materials are prohibited and non-synthetic materials are allowed for use in organic farming. The National List is the list of exceptions - synthetics that are allowed, and non-synthetics that are not allowed. Example: Hydrogen peroxide may be used organic farms
Who decides which inputs (fertilizers, pesticides, etc.) can be used on USDA-certified organic farms?
The National Organic Standards Board (NOSB) makes recommendations about this to the USDA, and the USDA then sets the standards. The NOSB is a group of 15 individuals (consumers, farmers, scientists, organic certifiers, food processors, etc.) that are appointed by the USDA to define and update the federal organic standards. OMRI (the Organic Materials Review Institute) reviews specific brands of materials to determine whether they comply with the USDA's organic standards.
What is the food system?
The food system encompasses all food production and consumption, ranging from manufacturing of agricultural inputs, farming, food processing, distribution, marketing, retailing and consumption.
If you had a choice between a two-year rotation (lettuce-tomato-lettuce-tomato) and a four-year rotation (lettuce-tomato-bean-onion), which would you choose and why?
The four-year rotation is better, for several reasons: -more time between similar crops, better chance of avoiding disease problems -less soil depletion because different crops place different demands on the soil -more crops are grown, so more biodiversity -the second rotation includes a legume in the mix, which is helpful for reducing N needs Lastly, if you look at the example in class of the Morrill plots, there is a chance that using a rotation with more crops will slow down loss of organic matter from the soil.
You take a soil sample that doesn't have any stones or large particulate matter. You give the sample to your favorite soil lab. They tell you that 30% of the sample consisted of particles that were too large to pass through a 0.5 mm sieve, and that, based on their testing methods, 40% of the original sample was silt. What is the texture of your sample?
The sample is 30% sand, 40% silt and 30% clay. Using the soil texture triangle, this is a clay loam.
Why is it important to incorporate (e.g., till into the soil) raw manure after spreading it (applying it to the field)? Give at least three reasons.
To avoid loss of nutrients due to volatilization and leaching, to avoid contamination of surface waters with nitrates and bacteria, to make sure that it's where the plants need it and can access it, to reduce odors...
What does it mean to 'turn' a compost pile, and why is it necessary?
Turning just means mixing the pile up. It is necessary because the bacteria need oxygen as well as the carbon and nitrogen found in the raw starting materials. Turning evenly distributes the oxygen found on the outside of the pile and the heat that builds up on the inside of the pile - both oxygen and heat are needed for effective decomposition.
What are some ways that farmers can promote biodiversity on their farm?
Varied land use near fields (hedgerows, woodlands etc) Beneficial insectaries Use organic sources of nutrients that require microbes to break them down Plant many types of crops
What did Justus Von Liebig discover, and how has it affected agriculture? `
Von Liebig discovered that there are 16 essential elements for plant growth (19 if you count Nickel, Silicon, and Sodium, which are not considered essential by most researchers). This discovery led to the development of synthetic fertilizers that added only the specific nutrients that were needed for plant growth, also known at the time of their development as "synthetic manures". Farmers rapidly adopted the use of synthetic fertilizers as they were much easier to transport and use.
Based on the studies we learned about in class, is there evidence that eating organic foods can change exposure to pesticide residues? Is this true for all types of pesticides?
We know that pesticide residues of all types are found less often on organic produce than on conventional produce. We also learned that diet replacement studies with children (feeding children organic instead of conventional diets for several days) dramatically reduced their levels of organophosphate pesticide metabolites found in their urine. Thus suggests that organic diets would reduce exposure to OP insecticides. However, the same was not true for pyrethroid insecticides - it appears that exposure in the diet is relatively insignificant compared with exposure via residential pesticide use (such as flea and tick collars).
Fish consumption has increased greatly worldwide since 1950. What role has aquaculture played in this? Where does aquaculture currently take place? What are some species that are currently farmed?
While wild harvest of fish increased continuously in the 60s and 70s, it has leveled off since the late 1980s. Farmed fish has taken off since about 1990 and is growing very rapidly. We (the U.S.) import most (84%) of the fish we eat; about 50% of it is now farmed in aquaculture systems. Most of the world's aquaculture takes place in Asia. Currently farmed fish include: shellfish, salmon, atlantic halibut, cobia, grouper, hybrid striped bass, trout, summer flounder, cod, rainbow smelt, sea urchins, oyster, and others.
There are two primary types of vascular tissue in plants. What are they, and what functions do they serve?
Xylem - water and nutrients are transported from the roots to the rest of the plant. Phloem - the carbohydrates produced during photosynthesis are transported from source (the photosynthetic leaves) to sink (any part of the plant that needs energy).
List and describe at least four things that you would learn about your soil from a standard soil test.
a. pH - tells you whether soil is alkaline (basic) or acidic. Plants grow best, because nutrients are most available to them, at a neutral pH. b. CEC - Cation Exchange Capacity indicates the soil's capacity to hold onto nutrients. In general, higher CEC values are better. c. Organic Matter - This is the percentage of the soil that is made up of living, decomposing, or already decomposed organic material. Higher levels of organic matter mean more nutrients available to plants, and organic matter positively affects soil structure (see question 1). In general, higher values are better. d. Macronutrients - with the exception of Nitrogen, the soil test tells you the level of many plant-available macronutrients (Mg, Ca, K, P). e. Texture - This is usually a special test, but labs canl tell you the texture class of your soil.
Crops that don't need reproduction
any crops where roots, stems, or leaves are harvested, such as lettuce, cabbage, celery, potato, carrot, kale, beet, leek, arugula, rhubarb, onion, etc.
Crops that need reproduction
anything where seeds or fruits are harvested, such as - tomato, pepper, melon, cucumber, apple & other pome fruits, cherry & other stone fruits, bean, pea, wheat, rice, oats, corn, sesame, safflower, nut crops, millet, etc.
Rosaceae
apple, pear, strawberry, plum, peach, brambles (raspberry, blackberry)
Fabaceae (legumes)
bean, pea, lentil, alfalfa, clover, soybean
Brassicaceae (crucifers)
broccoli, cabbage, cauliflower, kale, mustard
Poaceae (grasses)
corn, sugarcane, wheat, oat, rice
Apiaceae
dill, carrot, celery, fennel, cilantro
Conservation and augmentation
focuses on building naturally occurring populations of beneficial insects. An example we talked about was adding insectary plantings to provide nectar to aphid predators.
Nitrate (NO3)
found in soil, is available for plants to use
Ammonium (NH4+)
found in soil, is useful for plants (a few plants take it up directly, but most require that it be converted by microbes into NO3 first)
Nitrite (NO2)
found in soil, not taken up directly by plants
Nitrogen Gas (N2)
found in the atmosphere, not available for plants to use
feed conversion ratio
kg feed consumed per kg of animal product produced. This is a way to measure the efficiency of production.
Asteraceae
lettuce, artichoke, sunflower
Cucurbitaceae (cucurbits)
melon, cucumber, squash, pumpkin
TMR - Total Mixed Ration
mixture of forages, grains, proteins, vitamins and minerals that provide complete diet to livestock. This is often used in dairy and beef cattle production, and allows producers to refine diets to meet specific needs of animals at a given time.
What are some ways that farmers can limit biodiversity on their farm?
monocultures (low levels of "planned biodiversity") frequent disruption of habitats broad-spectrum pesticides
Alliaceae
onion, garlic, leek, chive
Solanaceae
potato, tomato, pepper, eggplant
Define polyculture. List the advantages and disadvantages of polyculture, as compared with monoculture.
the cultivation of more than one crop species on the same piece of land in various temporal and spatial patterns (over time and space) Advantages: slows spread of pests, more stable yield, insurance against crop failure of one crop, resources in the ecosystem are used more efficiently Disadvantages: complicated agronomic management, more host species may mean more pests and diseases at any one time.
Define gravitropism
the process by which plant roots grow in the direction of gravitational forces, and plant shoots grow in the opposite direction.
Inundative releases
this involves releasing large quantities of a predator or parasite into (usually) a controlled environment, such as a greenhouse, to temporarily control a pest problem.
Ammonia (NH3)
this is a volatile gas, not taken up by plants
Organic Nitrogen
this is nitrogen that's part of organic compounds within living plants and animals (like amino acids, DNA, etc). It is not available for plants until it is decomposed and broken down.
Rotational intensive grazing (AKA mob grazing)
this refers to a strategy of feeding pasture where herds are regularly moved to new pasture that has NOT been grazed recently. This allows the pasture to regrow and have optimum feed quality when it is grazed, and it also prevents undesirable species from taking over. One disadvantage of this system is that it can be very labor intensive.