Plants: Perennials and Annuals

Annual plants perform their entire life cycle from seed to flower to seed within a single growing season. All roots, stems and leaves of the mother plant die soon after it produces seeds. Farmers need to replant annual vegetables each growing season.

Perennials are plants that live more than two years. They regrow every spring with no replanting needed. Because the perennial doesn’t exhaust itself by growing and producing seeds in a short time span like an annual does, the mother plant can live ten year or more.

Make a Model
Due to the annuals’ short growth cycle, their root system tends to be shallow and need a lot of room. Corn is planted in rows 3’ apart with individual plants in each row about 1’ apart. Perennials grow more slowly and thus develop deep root that need less room. Switchgrass seeds are broadcast to produce a dense growth of plants.

Materials
 * two 9” square pans (cake pan work well)
 * block of floam (play dough can be substituted http://tinkerlab.com/rainbow-play-dough/)
 * about 70-80 wooden skewers
 * 1 ruler

Preparation
 * Make two identical “plots of farmland” by pressing floam to a depth of an inch over the bottom of each pan.
 * Label one pan “Corn Farm” and the other pan “Swithgrass Farm”
 * Put out skewers so they are available to all farmers.

What to do?
 * Form two team with 3 - 5 people (farmers) per team. One team will plant corn while the other team will plant switchgrass.
 * Give the Corn Team the Corn Farm and a ruler. Since corn need a lot area to grow, the corn farmers have to plant their corn plants in rows that are an 3” apart with each plant in the rows 2” apart.
 * Give the Switchgrass Team the Switchgrass Farm. Each switchgrass plant needs very little room to grow so the farmers can put the plants as close together as possible.
 * Give the farms a couple of minutes to discuss their planting strategy.
 * Both teams start planting their crops at the same time.
 * After 1 minuter, compare the two plots of land including number of plants on each plot and the relative density of both crops. The Corn Team can get a maximum of 20 plants on their farm (4 rows with 5 plants per row). The Switchgrass Team should be able to easily fit the rest of the skewers on their plot with room left over.

Game
Corn is currently the main source of ethanol in the US. It is relatively easy to extract ethanol from corn so production costs are low. On the other hand, corn is an ingredient in many foods and is used in the manufacturing of a wide variety of items (see Does It Contain Corn) which drives the cost of corn up. Like all annuals, corn grows from a seed to a mature plant in just a few months requiring a lot of nutrients in a short time. Farmers need to plant each corn plant 1-2 feet apart in rich soil, fertilize several times during the growth cycle and remove weeds regularly so they don’t use up the nutrients,  all of which cost the farmer money.

Like other perennial grasses, switchgrass grow slowly and thus can’t be harvested until it is a year old. However, once established the farmer doesn't have to replant for 10 or more years. Switchgrass grows well on marginal land with only light fertilization needed. The densely packed switchgrass plants crowd out any weeds providing a further savings for farmers. Finally, the conversion of switchgrass to ethanol is much more involved than corn’s conversion and thus is more expensive.

All these financial consideration need to be compared when deciding whether growing switchgrass for biofuel is cost effective. The following game is designed to help people understand the expenses and income expected for both corn and switchgrass as an ethanol source.

Materials 
 * poker chips: 15 red ($10 chips) and 10 blue ($5 chips) for each farm


 * to represent each farm use a piece of paper labeled “Corn Farm” or “Switchgrass Farm” where farmers can place each acre of land they purchaseFarm labels pdf.pdf
 * 3” square pieces of green paper each representing an acre of land: 5 blank squares for each Corn Farm; 12 squares for each Switchgrass Farm with a “1” on one side and a “2” on the other side (the square is placed with the “1” showing for the first year the farmer has planted the acre, it is flipped over to show “2” when the plants are more than a year old and are able to be harvested)


 * Corn Farm tally sheets and Switchgrass Farm tally sheetsTally sheets pdf-0.pdf

Set up

Transaction Explanation
 * divide participants into groups of 4-5 farmers
 * each groups chooses to grow corn or switchgrass on their farm (make sure there are at least one of each type of farm)
 * each farm selects one of their group to do transaction for the group
 * each farm sets a goal, either maximum profit (most $ in poker chips at end of 5 years) or maximum growth (the most acres of land at end of 5 years)
 * each corn farm receives: one corn farm sheet, one corn tally sheet, $40 in poker chips
 * each switchgrass farm receives: one switchgrass farm sheet, one switchgrass tally sheet, $40 in poker chips
 * farmers are given 5 minutes to manage their farms for 6 years
 * farmers can make transactions any time during the 5 minutes; there is no need to take turns
 * buy land
 * pay money to bank at time of purchase
 * collect acre of land from bank and place on farm sheet (switchgrass acre is initially put down with "1" face up for 1st year the land is planted then it is flipper over to "2" for all subsequent years
 * manage land
 * pay farming expense to bank at the beginning of each year
 * every year the corn farm must pay to plow and sow seeds, ferilizee several times, cultivate the land to remove weeds and harvest the corn
 * the first year an acre is used, the switchgrass farm must pay to plow and sow seeds and fertilize one time; the second year and every year thereafter the farm pays to fertilize one time and harvest the switchgrass at the end of the year.
 * after harvest, farms sell the biofuel and collect profits from the bank
 * end of game
 * count the number of acres on the farm sheet
 * count the poker chips the farm has
 * compare farms to see how each group did in meeting their goal
 * this model doesn’t try to show actual expenses and income but instead tries to demonstrate how the differences between an annual vegetable and a perennial grass translate into different expected costs and returns
 * land for corn is twice the price of switchgrass land because switchgrass can grow on marginal land while corn require big grade top soil
 * both corn and switchgrass require fertilization but corn need considerable more nutrients
 * corn incur cost for weed suppression but the switchgrass does not require any
 * corn is harvested and sold every year it is planted so it shows a profit immediately whereas switchgrass can’t be harvested until the grass has been growing for a year so there is no income the first year (also no harvesting cost)
 * corn sells for a higher price because it is in such high demand for other uses and it also has lower processing cost whereas switchgrass produces more biofuel per acre but the processing is more difficult and more expensive; to try and show this, the corn farm shows a profit of $40 per acre while the switchgrass farm shows $30 per acre after the 1st yearEthanol yield pdf.pdf
 * corn tends to be a steady income producer as long as the soil is maintained whereas the switchgrass starts out slow but after a couple of years is making more than the corn

Do Some Planting
Materials
 * vegetable seeds
 * switchgrass seeds
 * paper towel
 * stapler
 * resealable plastic bag
 * ruler
 * water
 * measuring cup
 * label

Procedure
 * fold a paper towel so that it just fits inside the bag.
 * take a ruler to measure 3” from the top of the bag and staple a row of staples from one edge to the other through the plastic bag and paper towel forming a mini-pocket, 3” deep for the seeds to sit in.
 * carefully pour 2 cup water into the bag so that it will soak up through the paper towel but leave a small reservoir of water at the bottom of the plastic bag
 * in mini-pocket put several vegetable seeds (depending on size) on one side and put a switchgrass seed on the other side
 * use permanent marker to label the two types of seeds
 * seal up the seed bag so no air can escape or get into it.
 * take home the bag with the seeds and tape it to a window
 * use take home worksheet to record germination progress of seeds
 * after several days you will see roots and seedlings beginning to form; carefully open your bag up and cut away the baggie
 * carefully plant the sprouted seeds into a pot of planting soil (seedlings are very fragile so make sure you handle them with care).