Agriculture


Garden Map
  1. Choose from the following plants: Basil, Beans, Bell Peppers, Broccoli, Cabbage, Carrot, Celery, Chili Pepper, Collards, Corn, Lettuce, Marigolds, Mustard, Onion, Oregano, Peas, Potatoes, Pumpkin, Spinach, Squash, Sunflowers, Tomato, Watermelon
  2. You will have about 9 square feet (an area that is 3 feet long and 3 feet wide).  You will need to find out the following information about the plants you want to grow:
    • How much space there should be in between plants
    • How much space there should be in between rows
    • When the plants should be started from seed
    • How long the plants take to grow
  3. I will get you the seeds and the soil.  You will need to determine which and how many of each plant that you want to grow, given the room that you have.  We will start by growing the seeds in the room, then you will help by working the soil outside and doing various chemical tests to see if we need any fertilizer.
  4. Make a map on a 3-foot by 3-foot grid containing all of the plants that you want to grow. Make sure to include appropriate spacing and companion plants.
  5. Determine exactly how many seeds and the optimal conditions for those seeds. Specifically, you should find out the amount of water, planting depth, soil temperature, soil pH, and anything else that is necessary for that particular seed.
  6. Ask for the appropriate materials and start to germinate your seeds!
Agriculture: Starting Seeds
In this activity, you will be starting the plants from seeds that you want to grow. You will need to find out specific information about each seed, such as:
  • Planting depth
  • Spacing
  • Time of year to start
  • Amount of sunlight needed
Using egg cartons and a mixture of potting soil and soil from the garden, you will start the seeds inside. Make sure to label each seed that you're starting and that you start about 3 seeds for every one plant that you want to grow.
Soil Preparation Techniques
After reading the following, respond:
  1. Compare conventional, reduced and conservation tillage in three ways using a chart or diagram.  Suggest which is the best type of tillage and why.
  2. Select two types of plows and compare them based on what they would be used for.
  3. What are two environmental concerns dealing with soil preparation?  What is the importance of each one?
  4. What are four ways to reduce erosion?  For each one, explain how we might be able to do that at Shaw.
Prior to planting, the soil needs to be prepared, usually by some form of tillage or chemical "burn-down" to kill the weeds in the seedbed that would crowd out the crop or compete with it for water and nutrients. Tillage methods can be divided into three major categories, depending on the amount of crop residue they leave on the surface. Residue slows the flow of runoff that can displace and carry away soil particles.
  • Conventional tillage - Until the last decade or so the standard tillage practice for corn was use of the moldboard plow for primary tillage followed by several secondary tillages and mechanical cultivation after the crop was up. Now about two-thirds of row crops are planted without use of the moldboard plow (Allmaras et al., 1997), and mechanical cultivation is often limited to one, or no operations.
  • Reduced tillage is usually done with a chisel plow and leaves 15% to 30% residue coverage on the soil.
  • Conservation tillage leaves at least 30% residue coverage on the soil. Conservation tillage methods include no-till, where no tillage is done at all and seeds are placed directly into the previous season's crop residue; strip-till, in which only the narrow strip of land needed for the crop row is tilled; ridge till; and mulch till.
Herbicides are used in all these methods to kill weeds. In no-till systems, the herbicide is applied directly on last season's crop residue. In the other methods, some soil preparation takes place before the herbicide is applied. A common myth is that more herbicide is used with conservation tillage methods, but in fact farmers rely on herbicides for weed control under all tillage systems, and the amount used is more or less independent of tillage method.
Soil Preparation Operations and Timing Tillage can occur anytime between harvest of the previous year's crop and spring planting. In the eastern Corn Belt, most tillage is usually done between March and May for corn, and can be as late as early June for soybeans. In some cases, tillage is done in the fall, after harvest. In southern states, planting can be considerably earlier or later because of their longer growing season. The optimum time for tillage (to prevent soil erosion) is just before planting. However, wet spring weather can often make it difficult to get equipment into the field as early as needed to optimize yield. Late planting can seriously reduce yields. For example, in the eastern corn belt, corn yields are reduced by 1 bu/acre for each day after May 1 that planting is delayed. Equipment Used for Soil Preparation Tractor Tractor - a traction machine that provides mechanical, hydraulic, and/or electrical power to implements to perform a wide range of crop production and handling operations. Tractors are most often used to perform drawbar work (pulling equipment through the field) and PTO (power take-off) (power to rotate equipment components) work. Tractors can be equipped with rubber tires, rubber belts, or steel tracks. A modern farm tractor is almost always equipped with a diesel engine and tractor size is measured by the amount of power that the tractor can produce at the PTO.  Tractor sizes range from those with less than 40 PTO horsepower to ones that produce more than 400 horsepower. The cost of a large modern tractor can be well over $200,000. Moldboard Plow Rubber-tracked tractor and moldboard plow at work in the field Plow - an implement used to perform primary tillage. A number of types of plows are in common use including the moldboard plow, the chisel plow, and the disk plow.  The moldboard plow has a large frame that is equipped with a series of "bottoms," each of which consists of a steel coulter to slice through residue followed closely by a steel share that cuts the soil and an attached moldboard that is used to raise and turn over the cut "slice" of soil.  Disk plows work in a similar manner to laterally displace and invert soil through the use of concave steel disk blades. Chisel plows use curved shanks to penetrate and "stir" the soil without inverting a soil layer. Chisel plows cause less residue disturbance than moldboard plows and are often used in conservation tillage systems. Close-up of Disk Harrow

A close-up view of a disk harrow in the field

Disk Harrows (or Disk) - are implements that uses steel blades to slice through crop residues and soil. Disk blades are mounted in groups or gangs that rotate as they move forward through the soil.  Front gangs move soil toward the outside of the disk while rear gangs move soil back toward the center of the disk. A disk can be used for primary or secondary tillage. Disk Harrow at Work

A field shot of a tractor and disk harrow at work

Row Crop Cultivator

A tractor and row crop cultivator working in soybeans plated with a conservation tillage system

Field Cultivator -an implement used to perform secondary tillage operations such as seedbed preparation and weed eradication. Field cultivators are equipped with steel shanks that are typically spring mounted to permit the shank to move within the soil and shatter clods. Field cultivators are constructed similarly to chisel plows, but are more lightly built. Large chisel plows can exceed 50 feet in width in the field.

Environmental Concerns Related to Soil Preparation: Soil Erosion

Soil Erosion The major environmental concern related to soil preparation is erosion. Soil erosion is a natural process that occurs when the actions of water and/or wind cause topsoil to be removed and carried elsewhere. Average Annual Soil Erosion Soil erosion can be caused by either water or wind. In many agricultural areas, soil is eroding at a rate of several tons of soil per acre per year or higher. The map shows an estimate of total soil erosion on agricultural areas in 1992. This includes both cropland and set-aside land in the Conservation Reserve Program. Forested and urban land is not included in the map. The good news is that soil erosion in the U.S. is decreasing. From 1982-1997, soil erosion declined about 40% in the U.S., due to government conservation programs, technological advances, and extension education efforts. Wind Erosion Area Water erosion is caused by the erosive power of raindrops falling on the soil (particularly if the soil is not covered by vegetation or residue) or by surface runoff. Raindrops cause the less severe forms of erosion (know as sheet and interrill erosion). Severe erosion problems such as rill erosion, channel erosion, and gully erosion can result from concentrated overland flow of water. Wind erosion is particularly a problem in windy areas when the soil is not protected by residue cover. Wind erosion in the United States is most widespread in the Great Plains states, as can be seen in the map at right. Wind erosion is a serious problem on cultivated organic soils, sandy coastal areas, alluvial soils along river bottoms, and other areas in the United States. Impacts of soil erosion Soil erosion has both on-farm impacts (reduction in yield and farm income) and off-farm impacts (contaminated water due to the sediment and associated contamination from nutrients and pesticides carried on the soil particle). On-farm impacts due to the loss of soil and nutrients include:
  • lower fertility levels
  • development of rills and gullies in the field
  • poorer crop yields
  • less water infiltration into the soil
  • more soil crusting
  • more runoff in the spring and after storms
When fertile topsoil is lost, nutrients and organic matter needed by crops often are removed along with it. Erosion tends to remove the less dense soil constituents such as organic matter, clays, and silts, which are often the most fertile part of the soil. However, the loss in productivity caused by erosion has not been so evident in many parts of the U.S., since it has been compensated for over the years by improved crop varieties and increased fertilization. Soils can tolerate a certain amount of erosion without adverse effects on soil quality or long-term productivity, because new soil is constantly formed to replace lost soil. This tolerable level is known as "T" and generally ranges from 3 to 5 tons per acre per year. Goals for reducing soil erosion often use the "T" value as a target, because erosion rates below T should maintain long-term productivity of the soil. Off-farm impacts occur when the eroded soil is deposited elsewhere, along with nutrients, pesticides or pathogens that may be attached to the soil. The tolerable"T" value described above does not take into consideration the off-farm or downstream impacts. Soil eroded by water has effects such as:
  • eroded soil deposited in depressions and adjacent fields
  • decreased water quality downstream
  • decline of downstream aquatic ecosystems because of sedimentation and the addition of nutrients, pesticides, and bacteria associated with the soil
  • clogged drainage ditches and other costly problems
Off-farm impacts of wind erosion are due to the blowing soil, which can reduce seedling survival and growth (seed cover), increase the susceptibility of plants to certain types of stress, contribute to transmission of some plant pathogens, and reduce crop yields. Dust affects air quality, obscures visibility which can cause automobile accidents, clogs machinery, and deposits in road ditches, where it can impact water quality.

Best Management Practices to Reduce Erosion

Conservation Tillage Conservation tillage leaves at least 30% residue cover on the ground. This simple, low-cost practice can have a huge impact on the amount of soil eroded. Because of energy savings and obvious improvements in soil quality that can result from conservation tillage, it has been widely adopted across the Midwest. In Indiana, for example, conservation tillage was used on 50% of corn and 80% of soybean acres in 2000, a dramatic improvement from 10 years earlier. There is still room for improvement, however. This map shows the percent of U.S. crop land currently in conservation tillage. Percentages are generally higher for soybeans than for corn or other crops. Contour Farming Contour farming and strip cropping is the practice of planting along the slope instead of up-and-down slopes, and planting strips of grass between row crops. Cover Crops Cover crops are crops such as rye that grow in late fall and provide soil cover during winter. By providing a cover to the soil, winter soil erosion from both air and water can be greatly reduced. Grassed Waterways Grassed waterways protect soil against the erosive forces of concentrated runoff from sloping lands. By collecting and concentrating overland flow, waterways absorb the destructive energy that would otherwise cause channel erosion and gully formation. Terraces Terraces are structural practices that can reduce erosion by holding back the water and routing it along a channel at a lower velocity to where it can be safely discharged, usually into a grassed waterway. Windbreaks Windbreaks are the best way to protect soil from wind erosion. They can be in the form of rows of shrubs or trees. Windbreaks Windbreaks Grass Barriers Grass barriers can prevent wind erosion by slowing the wind. Living Snow Fence "Living snow fences" prevent wind erosion by slowing the wind.
Effect of Fertilizers on Plant Growth

Procedures

  1. Design an experiment in which only one factor is varied: fertilizer, dosage or plant.
  2. Decide on a measurement: number of plants that die, the number of the top ten (or bottom ten) leaves that yellow.
  3. Administer the fertilizer, wait one week and make the appropriate measurements. Analyze the data.
History of Agriculture
In your group of three, choose one of the following time periods.  You will put together a chart and present it to the other group members (below).  You will select three "Big ideas" from your time period, and for each big idea, select three pieces of supporting evidence for that big idea.  Keep in mind you will be looking for general trends in what happened in agriculture during those time periods.
Big Idea:
Supporting Evidence #1:
Supporting Evidence #2:
Supporting Evidence #3:
oats “The most essential challenge for humanity is to learn to eat from nature’s bounty without destroying it in the process, to find our appropriate niche within nature.” ~ Judith Soule and Jon Piper Crop rotation can be traced all the way back to the ancient Roman, African, and Asian cultures. It has evolved alongside the progress of agriculture since the first domestication of plants. The benefits of such rotation were realized early and utilized to their full potential. Even in Europe during the Middle Ages farmers followed a three-year rotation pattern, planting rye or winter wheat during the first year, followed by spring oats or barley in the second year, and then no crops were grown in the third year. Later in the eighteenth century, British agriculturist Charles Townshend developed a four-year crop rotation of wheat, barley, turnips, and clover that aided the European agricultural revolution (Bellis 2005). This rotation has implications in the United States as well seeing as Europeans brought many of their domesticated plants and animals with them when they came to the New World. Settlement of America combined native plant and animal species with ones brought over from Europe and other world regions creating a new set of agricultural conditions. In the beginning the conditions of colonizing made subsistence farming the main form of agriculture. It was not until the frontier opened up and the idea of Manifest Destiny hit that American agriculture began down its own pathway of revolution. For my analysis I have broken down the history of American agriculture into three sections. I determined the breaks based on two significant turning points in the practice of agriculture, which had repercussions throughout the entire nation and world. The first break occurs in 1850 when the commercial corn and wheat belts began to form illustrating the initiation of what has become our current form of industrial agriculture. The second break at 1940 displays how technology and machinery shifted our system toward more industrial farm operations. Through analysis of our historical patterns the road to our current farming practices becomes clearly established. Wheat Farm Aitkin County, MN Photo courtesy of Minnesota Historical Society 1830s-1840s – Mechanical corn shellers are introduced 1831 – Cyrus H. McCormick developed the first commercially successful reaper, a horse-drawn machine that harvested wheat 1837 – John Deere invented the first cast steel plow 1842 – Joseph Dart invented the grain elevator 1849 – Minnesota was established as a territory 1850 – Edmund Quincy invented the corn picker, commercial corn and wheat belts began to develop, wheat occupied the newer and cheaper land west of the corn areas and was constantly being forced westward by rising land values and the encroachment of the corn areas, alfalfa was being grown on the west coast, successful farming on the prairies began With the onset of new machinery and farming practices, many of the old traditions of farming, including the culture that surrounded these activities, were left behind. Gene Logsdon shares a story illustrating the community and rituals that also were lost when traditional agricultural practices were replaced with more industrial farming techniques. "Before the industrial revolution, corn shocks were hauled in good weather to the barn, and then in harsh winter, the young people went from farm to farm in the evenings making a party out of the husking. The person who husked a red ear - and there were many red ears in the days before standardized hybrid corn - got to kiss his or her sweetheart. This was the cultural, even cultured, way of making work pleasant. It was replaced by a farmer husking corn alone in a cold December field, day after day - a misery, one he was driven to when technology made communal work impossible and obsolete, and when traditional social rituals had lost their significance (2000). Such enriching community experiences were replaced with more hectic and expensive lifestyles for the farmers and their families. In turn, these farmers were later replaced with more industrial agribusinesses that could shoulder the burden of mass food production. Our society has lost the local knowledge and community spirit that went hand in hand with traditional farming practices before the rise of commercial monocropping. The loss of human community parallels the weakening in the relationship between farmer and land as well. Wendell Berry states that the commercial version of agriculture explains to both farmer and consumer that "private knowledge, judgment, and effort can be satisfactorily replaced by generalized, expensive technological solutions (Jackson, Berry, and Colman 1984)." This idea really begins to show in the 1850s as crop rotation methods, whose benefits have been known since ancient times, are being replaced with commercial monocropping. The fact that the wheat belt slowly is pushed aside and taken over by the corn belt proves that general mass production is the encroaching goal encouraged by society, especially since corn is harder on the soil than wheat. In addition, these new heavy steel plows cause soil compaction problems. This new machinery is heavier than the old wood and animal contraptions of traditional farming and reduces water penetration and air supply to root systems, which in turn decreases crop yields. After such intense soil compaction the time it takes to irrigate that soil doubles and triples in length speeding the soil towards an unfertile future (Jackson, Berry, and Colman 1984). In Minnesota small farmers trying to make a living in the harsh Midwest environment were still practicing crop rotation late into the 1800s. Through the journals of Oliver Kelley we know that he raised corn, oats, wheat, hay, sorghum, and vegetables on his farm in addition to raising different kinds of livestock. Around 1874 Mary Carpent describes the layout of her farm in a letter: "The land here is rich and productive. We have in four acres broomcorn, four of corn, one of potatoes, and beans; besides quite a good garden." Most of this farming was only being done by subsistence farmers, as the commercial monocropping wave was approaching. 1850-1940 Steam Engine Powered Tractor Photo Courtesy of Minnesota Historical Society 1853 – George W. Brown invented the first corn planter, previously to 1850 corn had to be planted by hand 1855 – John Deere’s factory was selling over 10,000 steel plows a year 1858 – C. W. Marsh and W. W. Marsh invented the “Marsh harvester” 1862 – Homestead Act grants 160 acres of federal land to those who meet specific criteria 1868 – First steam engine powered farm tractors are used for general haulage and specifically by the timber trade 1880s – Heavy agricultural settlement on the Great Plains, the combine began to appear in experimental versions 1887-1897 – Drought reduced settlement on the Great Plains 1900-1910 – George Washington Carver developed his crop rotation method that revolutionized southern agriculture 1926 – First hybrid-seed corn company was organized 1930-1935 – Use of hybrid-seed corn became common in the Corn Belt 1932-1936 – Drought and dust bowl conditions developed Through the Homestead Act of 1862 there was a migration toward the Great Plains as people wanted land to farm and call their own. Those farmers who could prove that they had been residing upon or farming their land for five consecutive years were granted the claim to their land. Farmers could not get more than 160 acres or work more than one claim in a lifetime (Schlebecker 1975). Farming the prairies of the Midwest began to boom leading to the heavy agricultural settlement by the 1880s. Modern monocultures also dominated the Great Plains landscape now, decreasing soil fertility and depleting the soil of much needed nitrogen. In the south, monocropping of cotton, a soil-depleting crop, had lead to soil degradation. George Washington Carver, while a teacher at the Tuskegee Normal and Industrial Institute for Negroes, developed a crop rotation that would help revive the southern soil. Carver advocated that farmers alternate soil-depleting crops, such as cotton, with soil-enriching crops, such as peanuts, peas, soybeans, sweet potatoes, and pecans (Bellis 2005). Through this cycle the south underwent their own agricultural revolution that renewed their soil and in doing so their connection with the natural processes of the land. Unfortunately the Great Plains was suffering from drought conditions and the harsh use of their soil was emphasized. The dust bowl and depression were well on their way. "By 1933, at least 50 million acres had been laid waste. Land reduced in usefulness by half through erosion came to another 125 million acres. The destruction had, in fact, just begun (Schlebecker 1975)." In 1935 Congress created the Soil Conservation Service in order to save the fertility of the soil. Several projects were developed to help stop erosion and renew the soil fertility. Crop rotation occurred sporadically as did cover crops and contour fields. With the onset of the dust bowl drastic measures were needed. The main projects included planting drought-resistant trees that did help with soil erosion problems, but were eventually cut down and used by farmers for fuel. The primary lesson that came about through the dust bowl was the need for fertilizers and manures, a mistake American farmers would never make again (Schlebecker 1975). This changed the face of American agriculture once again as fertilizer use becomes a solution and a problem all of its own. 1940-1990 Minneapolis Moline Tractors Coming off the Assembly Line Photo courtesy of Minnesota Historical Society 1940 – Big changes due to the increased use of tractors, crops used for livestock feed, such as oats, dropped 1943 – DDT becomes available in the United States 1944 – Discovery of effective herbicides 1945-1955 – Increased use of herbicides and pesticides 1946 – Self-propelled corn picker is placed on the market 1950s – Many rural areas suffer population losses as many farm family members sought outside work 1956 – Legislation passed providing for Great Plains Conservation Program 1960s – Soybean acreage expanded as farmers used soybeans as an alternative to other crops 1980-1990 – Biotechnology research gets underway 1985 – Farm Bill created the Conservation Reserve Program 1988 – One of the worst droughts in the Nation’s history hit midwestern farmers 1990 – Farm Bill provided the first national standards for “organically grown” labeling As tractors became available and affordable to all farmers the efficiency with which large acres of land could be cultivated increased and therefore industrial methods of agriculture increased right alongside leading us into the era of agribusiness. Interestingly enough, World War II aided this movement by creating the conditions needed to discover herbicides and pesticides. Scientists were working to discover chemicals or other agents that could be manipulated to kill only one specific type of vegetation. Through their research they came across DDT and some of the more effective herbicides. Biological warfare helped lead the way to our modern system of agriculture. In conjunction with the rising of industrial farming smaller family farms were decreasing. "In 1900, there were 5.7 million farms in the United States, averaging 138 acres apiece. By 1978, the number had dropped to 2.5 million, and their average size was 415 acres. (Jackson, Berry, and Colman 1984)." Industrial agribusiness has taken the 'culture' out of agriculture, as Wendell Berry would say. Food production has become a business only corporations seem to be allowed to participate in. Crops are seen as commodities and traditional farmers as we know them are all but disappeared. The local knowledge and connection to the land and its processes are on the verge of being lost as well. As we hit the 1960s hopeful movements can be seen that are trying to renew the relationship between land and farmer, or corporation, as may be the case. The idea of crop rotation is resurfacing as the ancient benefits are once again realized. Soybeans are introduced only the first step towards a more diverse and sustainable agricultural system. The farm bill of 1985 was unproductive in that it "required farmers with highly erodible land to design approved conservation plans by 1990 to remain eligible for any government farm support or loan program, [however], other provisions still made farmers lose benefits if they used crop rotation (Soule and Piper 1992)." The 1990 farm bill changed this ruling so that farmers could use crop rotation and were even encouraged to do so. We are currently in a period where research is being done to discover more sustainable agricultural practices as we realize that our modern industrial system is unhealthy for humans and the environment alike. Crop rotation has been a valuable method of sustainable agriculture known by ancient civilizations and historical settlers alike, forgotten through the industrial and technological revolution that has taken hold of our country. It is time to rediscover this important tradition and all its benefits in order to restore balance to our relationship with nature and save the health of our society.
Monocot vs. Dicot
  1. How are monocots and dicots different?  List at least four ways.
  2. Monocots have one cotyledon in the seed. A cotyledon is the structure of seed plant embryo that stores or absorbs food for the developing embryo: may become the plant' first leaves when the plant emerges from the soil. One type of veins in the leaves (veins go in one direction), and one type root system (the same type of roots).
  3. What is the meaning of the prefix mono?
  4. Get a corn seed and a bean seed.
  5. Draw the monocot seed.
  6. List the characteristics of the monocot.
  7. Draw the dicot seed.
  8. List the characteristics of the dicot.
  9. Remove the seed coat from the seeds.  What do you notice?
  10. Take a walk outside. For each of 5 plants that you find, name them and identify them as monocots or dicots.
Pest Identification and Protection
Go to http://www.beyondpesticides.org/alternatives/factsheets/index.htm . For three of the pests listed (different ones than the others in your group), make a quick poster with:
  1. A labelled sketch of the pest in the middle
  2. Two - three methods of prevention on the top half
  3. Two - three methods of control on the bottom half
Irrigation
After reading, you should be able to answer the following questions:
  1. How much water to vegetables need every week?
  2. What can be used in order to measure the amount of rainfall that falls in a week?
  3. How much water can the top level of soil hold?
  4. How can you increase the amount of water that is held by the soil?
  5. How does mulching help irrigation?
  6. For one of the crops that you are growing, what is the critical irrigation period?
  7. What are two benefits of irrigation?
  8. When should you and should you not irrigate a vegetable garden?
  9. What is one pro and one con of drip irrigation?
  10. What is gray water, and why is it used for irrigation?
  11. Which irrigation system should we use and why?
Adequate soil moisture is essential for good crop growth. A healthy plant is 75 percent to 90 percent water. The plant needs that much water to carry out vital functions, including photosynthesis, support (rigidity), transpiration, and transportation of nutrients and sugars to various parts of the plant. During the first two weeks of growth, plants are becoming established and must have the proper amount of water to build their root systems. Too little water can stunt or even kill tender seedlings, while excessive moisture can prevent roots from moving out into the soil searching for water and nutrients. Without a sufficient root system, hot, dry weather can adversely affect vegetable plants as they mature. In areas prone to repeated drought, select drought-resistant varieties when buying seed or plants. During the growing season, from April to September, vegetable crops need enough water each week to wet the soil to 5 to 6 inches. In most soils, this is about 1 inch applied at one time in the form of rainwater, irrigation water, or both. However, some vegetables, like tomatoes and muskmelon, may require close to 2 inches of water per week for optimum production. Keep a rain gauge near the garden or check with the local weather bureau for rainfall amounts, and then supplement the rainfall with irrigation water, if needed. There are ways, however, to reduce the amount of water you have to add. When overhead watering bare-ground crops, one thorough watering each week of 1 to 2 inches of moisture (65 to 130 gallons per 100 square feet) at one time is usually enough for most soils. Wet the soil to a depth of 5 to 6 inches each time you water and do not water again until the top few inches of soil begin to dry. Trickle or drip irrigation systems use water much more efficiently. When you use a drip system, especially in combination with mulch, you will use a more frequent or continuous application of water in smaller amounts to maximize vegetable production. Even when you use a drip or trickle system, a good thorough wetting of the soil once a week for the first couple of weeks is the best technique to develop healthy root systems. During those times when cultural practices simply aren’t enough, when rainfall is sparse, and the sun is hot, watering can benefit the garden with higher yields and may save the garden altogether in severe drought years. Irrigation as a Water Deposit When irrigating vegetable plants, it is easy to think that you are “watering” the crop. What you are really doing is adding water to the soil. Think of this process as “making a deposit” into the water reserves. When the plant uses water, it is making a withdrawal. Just like a checking account, you can only withdraw what is in the account. When it is empty, the plant wilts and dies. Unlike a checking or savings account, however, the soil will only hold so much water. The top 12 inches of soil will generally only hold 2 to 4 inches of available water, depending on the soil type. Applying more than 2 inches, even to dry soil, may result in wasting water. Reducing Water Demands All of the water you apply may not be available to plants. This is particularly true with heavy clay soils. Clay particles hold soil moisture tightly. If, for example, there are 4.5 inches of water per foot in this type of soil, there may be as little as 1.5 inches available for plants. A relatively high level of humus in the soil, brought about by the addition and breakdown of organic matter, can improve this proportion to some extent. By causing clay particles to form aggregates or large clumps of groups of particles, humus also adds air spaces to tight clays, allowing moisture to infiltrate the soil, instead of puddling and running off the top of the soil. The moisture-holding capacity of sandy soils is also improved by the addition of organic matter. Although most soil water in sandy soil is available, sandy soils typically have low water-holding capacities. The water drains through sandy soils so quickly that plant roots are unable to find much water even a few days after a rain. Humus in sandy soil gives the water something to cling to until the plants need it. Adding organic matter is the first step in improving moisture conditions in the garden. Mulching Mulching is a cultural practice that can significantly decrease the amount of water you need to add to the soil. A 2- to 3-inch (6 to 8 inches of loose straw or leaves will compact to 2 to 3 inches of mulch) organic mulch can reduce water needs by as much as half. Mulches smother weeds, which take up and transpire moisture, and reduce the evaporation of moisture directly from the soil. Organic mulches themselves hold some water and increase the humidity level around the plant. If the mulch becomes dry, it may be necessary to add an extra 1 or 2 inches of water to soak through the mulch when doing overhead watering. Black plastic mulch also conserves moisture, but may increase soil temperatures dramatically during the summer (to the detriment of some plants and the benefit of others) if not covered by other mulch materials or foliage. (See Mulches for the Home Garden, Virginia Cooperative Extension publication 426-326, http://pubs.ext.vt.edu/426-326/.) Shade and Windbreaks Shade and windbreaks are other moisture conserving tools. Plants that wilt in very sunny areas can benefit from partial shade during the afternoon in summer. Small plants, in particular, should be protected. Air moving across a plant carries away the moisture on the leaf surfaces, causing the plant to need more water. In very windy areas, the roots often cannot keep up with leaf demands, and plants wilt. Temporary or permanent windbreaks can help tremendously. Critical Irrigation Periods By knowing the critical watering periods for selected vegetables, you can reduce the amount of supplemental water you add. This can be important where water supplies are limited. In general, water is needed most for germination of seeds, immediately after transplanting, during the first few weeks of development, and during the development of edible storage organs. Following are critical periods for selected vegetables.
  1. Cauliflower - Head development
  2. Corn, sweet - Silking, tasseling, ear development
  3. Cucumber - Flowering, fruit development
  4. Eggplant - Flowering, fruiting
  5. Lettuce - Head development; moisture should be constant
  6. Melons - Flowering, fruit development
  7. Peas - Pod filling
  8. Tomato - Flowering, fruiting
Irrigation Benefits Irrigation practices, when properly used, can benefit the garden in many ways:
  • Aid in seed emergence
  • Reduce soil crusting
  • Improve germination and plant stand
  • Reduce wilting and checking transplant growth
  • Increase fruit size of tomato, cucumber, and melon
  • Prevent premature ripening of peas, beans, and sweet corn
  • Maintain uniform growth
  • Improve the quality and yield of most crops
Irrigation Methods As a home gardener, you have several options for applying water to plants. Most gardeners either use overhead watering (a sprinkling can, a garden hose with a fan nozzle or spray attachment, or portable lawn sprinklers). You can also use drip or trickle irrigation, which includes soaker hoses (an extrusion product of ground up tires), thin wall drip irrigation tapes, drip emitters, and spray stakes. When properly cared for, quality equipment will last for a number of years. Some basic techniques and principles for overhead irrigation: Adjust the flow or rate of water application to about 3/4 to 1 inch per hour. A flow much faster than this will cause runoff unless the soil has exceptionally good drainage. To determine the rate for a sprinkler, place small tin cans at various places within the sprinkler’s reach, and check the level of water in the cans at 15-minute intervals. When using the oscillating type of lawn sprinklers, place the sprinkler on a platform higher than the crop to prevent water from being diverted by plant leaves and try to keep the watering pattern even by frequently moving the sprinkler, overlapping about half of each pattern. Do not wet the foliage in the evening; this can encourage diseases. Early-morning watering is preferred. It is best to add enough water to soak the soil to a depth of 5 to 6 inches. This requires approximately 2/3 gallon of water for each square foot or 65 to 130 gallons for 100 square feet of garden area. This varies with soil type. Frequent, light irrigations will encourage shallow rooting which will cause plants to suffer more quickly during drought periods, especially if you do not use mulches. On the other hand, too much water, especially in poorly drained soils, can be as damaging to plant growth as too little water. Drip or Trickle Irrigation Several types of drip or trickle equipment are available. The soaker hose is probably the least expensive and easiest to use. It is a fibrous hose that allows water to seep out all along its length at a slow rate. However, this is not an engineered product and tends to lack uniformity of application. Soaker hoses also make great chew toys for critters like ground squirrels. There are also hoses with holes in them that do basically the same thing; water drips out the holes (drip irrigation tape). With the latter type, a flow regulator usually has to be included with the system so water can reach the end of the hose without bursting the tape from too much pressure. Most drip tapes are designed to operate at 8 to 12 psi. Pressure-compensating drip tape has been developed that maintains an even flow across the length of the tape even on uneven slopes. Place perforated plastic hoses or soaker hoses along one side of the crop row or underneath the mulch. Allow the water to soak or seep slowly into the soil. Finally, there is the emitter-type system in which short tubes, or emitters, come off a main water supply hose. Emitters put water right at the roots of the desired plants. This is generally the most expensive form of irrigation and the most complex to set up, but it has the advantage that the weeds in the area are not watered and evaporation from the soil is minimized. This type of system is best used in combination with a coarse mulch or black plastic and for small, raised-bed or container gardens. Drip systems generally have some problems with clogging from soil particles and/or mineral deposits. All water, including municipal water sources, should be filtered. Due to possible sand and silt particles, well water is subject to plugging emitters more than municipal water and must be filtered. To prevent plugging, always install drip tapes or emitters with the holes pointing up. It is wise to make a complete investigation and comparison before purchasing a drip irrigation system. Gray Water If water supplies are short in your area and you consider using gray water (water from household uses) on your vegetable garden, you should know that at the time of writing this publication, it is illegal to use untreated gray water for irrigation in Virginia. For more information on water “reuse,” please refer to Water Reuse: Using Reclaimed Water for Irrigation, Virginia Cooperative Extension publication 452-014 (http://pubs.ext.vt.edu/452-014/). For more information on gray water usage and regulations, please contact the Virginia Department of Health. In those states where the use of gray water is allowed, the following rules are recommended: Do not use “black water” (any water run through the toilet) because of the possibility of contamination from fecal organisms. It is best not to use kitchen wastewater that contains grease, harsh cleaners, ammonia, bleach, softeners, or nonbiodegradable detergents. If using water from the bathtub or washing machine, use only mild, biodegradable soaps. Omit softener sand bleaches. Allow wash and rinse water to mix, if possible, to dilute the soap content. Never use a borax-containing product (such as washing soda) in water to be used on a garden because of the danger of applying toxic levels of boron. Apply gray water to the soil, not to plant leaves. In summary, good irrigation practices are critical to good plant growth and fruit production. In addition, good irrigation practices are efficient and conserve water while providing for the plant’s needs.
Final Project: Agriculture
Your objective for this project will be to clear, weed, grow and tend to the garden. You should include all of the following aspects of agriculture in your final paper:
  • Pest identification and prevention
  • Prevention of soil erosion
  • Use of sustainable tilling methods
  • Use of appropriate fertilizers (if any)
  • Identification of proper irrigation techniques
  • Plan for maintenance of the garden over the summer
With my assistance, you will create a posted sign that will introduce people to the garden, the plants that are growing inside of it, and a variety of techniques that you have learned and utilized. This sign should be 1' x 1' in size and will be mounted on wood, protected by glass. You should include pictures and make sure that the sign is both self-explanatory and attractive.