HORT 3300E Final
Know the reasons drip irrigation makes sense for an organic gardener and EXPLAIN (at least one reason should be specific to organics).
Drip irrigation minimizes periods of leaf wetness, making plants a less appealing habitat for bacteria and pathogens, which are a big issue for organic growers. Drip also minimizes splash, which in turn minimizes the splash spread of pests and disease. Drip irrigation requires less water than other forms of irrigation, which places less stress on water supply (especially with city water). This also reduces the cost. Drip irrigation delivers water directly to a specific location of the soil rather than broadly spraying, which minimizes opportunity for water landing on above-ground plant parts, expedites the delivery of water to the roots, and makes it easier to deliver an even amount of water to each crop in the field. This also minimizes evapotranspiration. Drip irrigation is easier to install than other irrigation methods since it does not require any glue or heavy machinery. Most drip irrigation systems can be pieced together not unlike Legos or Linclon Logs.
Components of the Organic Foods Production Act (1990) and the National Organic Standards of 1990 (revised 2002)
The Organic Foods Production Act (OFPA) called together a board to determine national organic standards, which were released in 1999 and went into effect in 2001. The National Organic Standards are a system that is managed in accordance with the USDA regulations and responds to site-specific cases by integrating cultural, biological, and mechanical practices that foster the cycling of nutrients, promotes ecological balance, and conserves biodiversity. The National Organic Program develops, implements, and administers the national production, handling, and labeling standards for both fresh and processed agricultural products (crops and livestock). The Organic Materials and Review Institute (OMRI) is a nonprofit in charge of approving growing operations for organic production and maintaining organic standards. To be approved, growers must contact an agent, provide a three-year history of any and all substances applied to the land, a list of any organic products grown/raised/processed, and a written plan for crops to be grown and appropriate management strategies (substances, practices).
Know the model for a biologically-based IPM program. Describe each component and explain its relative importance to the overall program.
The bottom and most important tier of the IPM pyramid is pre-plant considerations, especially the soil health. Such considerations include OM content, soil fertility, site selection, and rotation. The second tier of the pyramid is biological control. This tier includes predatory insect/pathogen/parasitoid release, and aims to enhance the in-soil and above-ground biodiversity. The third tier of the IPM pyramid is physical amendments. These are enacted during the growing season, and include physical changes to the crop's environment such as netting, traps, lures, etc. The top tier and least important aspect of IPM are control products, and should only be used as an absolute last resort, especially because any pesticides with organic approval are generally unreliable.
Nitrogen mineralization stages and inputs/outputs
mineralization (nitrogen to ammonium) --> nitrification (ammonium to nitrates) (nitrates taken up by plant) --> denitrification (release of gaseous nitrogen in low-oxygen conditions) --> immobilization
What form of nitrogen is taken up by the plant?
nitrates (NO3-), less often ammonium (NH4+)
What are the ideal environmental conditions for nitrogen mineralization?
wet, loose soil with high OM content
Know the components of a drip irrigation system and why they are critical to a drip system operating properly.
A drip irrigation system consists of a water line (provides water), possibly a timer (turns system on/off), a filter, a pressure regulator, drip tube connectors, and the drip tubes themselves (deliver the water). The most important parts of a drip irrigation system are the filter and the pressure regulator. The filter removes any large dirt or debris from the system, which is important because the small holes that release the water in the drip tubes can become clogged easily, and a single clog can ruin the irrigation of the entire system. The pressure regulator is important because the whole point of drip irrigation is to have a slow flow of water, and most city water runs at a much higher pressure than is meant for drip irrigation. If water at too high of a pressure enters the system, it can interfere with the planned watering of any crops on that system or even burts the drip tubes.
Why is it difficult to grow organic vegetables using a solution-based hydroponic system? Describe the process by which this nutrient would become available to plants in an aquaponic system.
Aside from the conflict of hydroponics with traditional organic philosophy, it is very easy for hydroponic systems to deliver too much of a given nutrient to the plants, especially Nitrogen. Additionally, disease spreads quickly and is more debilitating in a hydroponic system because all of the plants share the same water supply, and organic growers do not have access to the same caliber treatments as conventional growers do. In an aquaponic system, plants grow on a medium with their roots in a water solution. The water has fish living in it, which provide Nitrogen expelled by their gills and feces. That Nitrogen, which is toxic to the fish, is converted into Nitrate by bacteria on the surface of the plants' growing medium to be taken up and used by the plants. These bacteria are the same as would be present in the soil in a traditional organic growing operation, and often arrive on the medium naturally. Any additional requirements or aeration needed by either the plants or the fish can be dissolved into the water or introduced into the fishes' food.
Conditions that enhance use of beneficial insects and harm beneficials.
Farmscaping is the practice of planting to encourage beneficial insect longevity, and is the best way to enhance beneficials. Farmscaping practices include planting companion crops that may provide additional food or shelter to the beneficials in times of low pest populations. Other beneficial practices include the planting of trap crops and resistant crop varieties. Practices harmful to beneficial insects include use of broad-spectrum pesticides (conventional, pyrethrin, etc.) and the use of reflective mulches, which has the same negative effect on beneficials as it does pests.
Why are fruits more challenging for organic?
Fruits are more challenging for organic growers because they are very disease-prone, but there is only emergency access to the pesticides and other spray similar to what a conventional grower would apply. Tillage and crop rotation, two important tools in an organic grower's pest and disease management strategy, are not available for fruit crops due to the permanent nature of their placement.
How do beneficial insects work to control harmful insect pests? If a beneficial insect is purchased and released, what level of control would you expect (explain)?
Inundative control is the release of predators in order to control a specific insect at a given time, though this management method can get expensive. Predators allow one predator to eat mant pests. Parasitoids allow one or many parasitoids to consume a single pest. Microbes compete with harmful bacteria/pathogens in order to suppress pathogen populations. Beneficial insects have no loyalty to their release site, so if the environment of your farm is not well-suited to their needs, they can just go away. That being said, beneficial insect release is most successful in greenhouses and pocket locations.
How is pesticide toxicity measured?
LD 50, or the amount of a pesticide required to be lethal for 50% of a tested population. For example, a high LD 50 value would indicate a less harmful pesticide than a low LD 50 value.
Describe steps involved in getting an organic pesticide approved and how it is different from a "conventional" pesticide. What agencies are involved?
OMRI-approved pesticides must degrade quickly and have a relatively high LD 50 value, and they must only be used as a last resort within an IPM strategy. Conventional pesticides generally work much quicker and more efficiently than organic, but they also tend to remain in the soil for longer periods of time and are more toxic overall.
Know the fundamental differences in growing most fruits in Georgia versus growing vegetables.
One fundamental difference in the production of fruits from that of vegetables is that the site selection is permanent. This means that spacing is very important, and that soil must be in an ideal, long-lasting condition before the trees are grafted. Additionally, a minimum number of chilling hours must be met in order for the tree to put out blossoms and eventually produce fruit. If this requirement is not met, the tree will give minimal yield or not produce any fruit at all. Fruit trees are also more expensive per acre than vegetable crops. Many fruits also bloom in early spring, so their blossoms are susceptible to frosts that may also kill off and possible fruits for that growing season.
Explain how the pesticide Pyrethrin could do more harm to the environment than some "conventional" pesticides.
Organic growers have been trending away from Pyrethrin use in recent years due to its non-targeted, yet relatively severe, approach to pest control. Pyrethrin will instantly kill anything in the field, and has also been demonstrated to be harmful to fish in field runoff.
Know three reasons why weeds pose a problem for food crops and be prepared to describe 3 organic methods used to control weeds.
Problems posed by weeds include competition for resources and light, shelter for pests and pathogens, interference with harvesting operations, and allelopathic effects which may stunt the growth of surrounding plannts. Weeds may be controlled organically by maintaining proper care and health of the soil, which discourages the introduction of weeds in the first place. Proper tillage, especially, can physically disrupt the growing of weeds and any remaining seeds from previous seasons. Any equipment or new seeds/transplants should also be inspected for signs of weed harboring prior to planting. Cover cropping can take up soil space between growing seasons so that weeds cannot establish themselves. Mulching physically keeps weeds in the ground. Solarization and plastic soil covers heat up the soil in order to kill any weeds before they can emerge.
Describe solarization as an organic pest control method and how a gardener would solarize their soil. Know reasons why one would solarize and what would be the negative consequences of solarization.
Solarization is the heating of the soil in order to kill off any lingering pests, bacteria, or weeds. Solarization may be accomplished by covering a section of soil with clear plastic for the warm summer months and leaving it in the sun, and is more effective in climates that receive a high degree of solar radiation. In-season solarization may also occur with raised beds, green houses, or high tunnels. Solarization kills off harmful pests, pathogens, and weeds, but it also has the potential to harm beneficial OM present in the soil.
Law of Minimum and Law of Returns- the originators of these theories and where they fit into current gardening practices.
The Law of Minimum, originated by Justus von Liebig, states that plants only need to meet the minimum requirement of each of a given nutrient (Nitrogen, Potassium, Phosphorus, etc.) in order to grow and thrive, and is often used to justify the use of artificial fertilizers. The Law of Returns, originated by Sir Albert Howard, states that the soil and the farm as a whole function as a system that breaks down organic matter into the nutrients necessary for growth.
Be able to describe the best soil, climate, and plant conditions for transplants versus seed. Why do people use transplants and why would anyone sow seed instead of using a transplant?
The benefits of transplants include an extended growing season, easier early-life management, and lesser crop loss due to thinning. It is ideal to plant transplants in the early morning of a low-wind, high-humidity day, in misty rain possible. The soil should be from 50%-70% field water capacity, and it should be freshly tilled and loose with temperature suited to the individual crop. The plant should have 1-2 sets of true leaves, and an established root ball that reaches to the bottom of its container. It should also have undergone a hardening off period to transition from the green house to outdoors. Plants should also be inspected for any signs of disease or pests prior to planting. After planting, the plants should be watered into the ground to promote the setting of soil. The benefits of seed include lower actual cost and easier planting/dispersal. Quick-germinating varieties also do better when seeded directly into their plot versus moving as a transplant. Seeds should be planted in the early morning on a low-wind, high humidity day, with misty rain if at all possible. Soil should be tilled to eliminate the presence of clods and maximize seed-to-soil contact, and should be from 50%-70% of field water capacity at a temperature ideal for the specific crop. Seed should also be watered in, but to a lesser extent than transplants. Barriers should also be in place to eliminate the opportunity for seed to be eaten by predators, such as birds and raccoons.
Name the four life stages of complete metamorphosis and explain how/why management of that stage is easy/difficult and what possible organic practice (if any) could be employed. DO NOT USE HAND-PICKING AS A POSSIBLE BENEFIT
The complete metamorphosis of an insect moves from egg, to larva, to pupa, to adult. The egg is well-protected from its environment, so topical treatments (pesticides, neem, etc. do not work well. Eggs can be eaten by predators, so biological management is a viable option. Pest larvae are voracious feeders, so any ingested control methods work well. Many parasitoids also prefer to lay their eggs in the larval stages of pests, so biological control is also an option. However, larvae can be difficult to identify, complicating the process of choosing an appropriate biological control process. The pupal stage of insect metamorphosis is difficult to control organically, especially because the pupae do not eat at all. The pupae also do not move, so traps do not have much of an effect, and they are resistant to many topical forms of pest control. There are a variety of methods to discourage adult insects from pestering crops. Reflective mulch can interfere with landing and orientation capabilities, discouraging pests from landing on plants in the first place. Row covers and netting can also prevent pests from landing on plants. Traps can physically collect the insects, especially pheromone traps, which also interfere with mating behavior to discourage reproduction. Regardless of life stage, general control strategies to discourage the movement of pests on plants include diatomaceous earth (shreds the pest), garlic barriers, and hot pepper wax (burns the pest).
What are the three points of the disease triangle and how can they be manipulated.
The disease triangle is comprised of host, environment, and pathogen. The host portion can be manipulated by choosing disease-resistant cultivars, inspecting seeds/transplant material for signs of disease/weakness, and avoiding planting more than one selection from the same crop group in the same field within a 2-3 year rotation cycle. The environment can be manipulated by choosing a host well-suited to the environment, minimizing wet periods, and maintaining optimal soil health and nutrient levels. The pathogen can be manipulated by pruning between seasons to remove saprophytes/mummies, minimizing opportunity for splash-spread of pathogens, and having a general awareness of diseases common to your crops and climate and being able to identify the early signs of infection.
Why is it easier to grow fruit in California?
The hot and humid climate of Georgia is more well-suited to pests and disease than the hot and dry climate of California.
What is the balance of soil water, air, minerals, and OM in percentages? Understand gardening practices that might negatively affect that balance and practices that could improve or maintain that balance.
The ideal soil is 25% water, 25% air, 45% minerals, and 5% OM. Negative practices include tilling while wet (clods) and over-tilling (pans, erosion, decreased AWC). Beneficial practices include cover cropping (maintain texture, fix Nitrogen) and addition of OM (prevents compaction and increases AWC, CEC, pore space, disease resistance, and breakdown rate of chemicals), which can be accomplished with manure/compost.
Are the Law of Minimum and the Law of Returns mutually exclusive?
The two laws are not mutually exclusive of one another, but the Law of Minimum has often been used as an argument against organic agriculture, which is founded on the Law of Returns. Both laws state that properties of the soil determine plant health/yield, but the Law of Minimum disregards the benefits of soil structure/OM. The Law of Minimum focuses on specific numbers and ratios, while the Law of Returns provides more general guidelines.
