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Lesson plan Grade 5 Science

Tannerly Orchard's Drip Lines: Where a Peach Tree's Mass Comes From

A grade 5 science lesson where students weigh evidence that a peach tree is built from air and water, then multiply decimals to compare drip and flood watering.

Objectives

  1. Students will use weight evidence to argue that a tree's added mass comes mostly from air and water.
  2. Students will multiply and subtract decimals to compare drip watering with flood watering.
  3. Students will explain how drip lines lower the water an orchard uses on each tree.

Vocabulary

Key words: irrigation, drip line, emitter, mass, evidence

Teacher overview

Tannerly Orchard is a fictional peach orchard that replaced its flood irrigation with drip lines, and its record book anchors this lesson. Students first argue about where the wood, bark, and fruit of a growing tree actually come from, then use the orchard's watering numbers to compare the two watering methods with decimal multiplication. The misconception this lesson is built to correct is the common student belief that a tree gains its weight by pulling soil in through its roots, which leads students to predict that the pot of soil around a growing tree should get much lighter. The orchard's record shows the tree gaining tens of pounds while the soil loses a fraction of a pound, and that gap is the evidence students reason from.

Procedure

Hook (8 min): Set a small pot of dry soil on the scale and record its weight where the class can see it. Ask students to picture a peach pit planted in that pot and growing for three years into a tree taller than they are. Ask one question and collect answers without judging them: where does all that new wood, bark, and leaf material come from? Write every prediction on chart paper. Most classes name the soil first.

Direct instruction (12 min): Explain that growers have tested this question by weighing a potted tree and its soil at planting and again years later. Tell students what the record at Tannerly Orchard shows, which is that the tree gained many pounds while the dry soil in its pot lost only a small fraction of a pound. Ask what that leaves as the source of the new material, and steer the discussion toward the two things a tree takes in constantly, which are air and water. Write the words mass and evidence on the board and define each one plainly.

Guided practice (10 min): Introduce the orchard's watering system. Each tree has two drip emitters, and each emitter releases a measured amount of water each hour directly at the roots. Work one example with the class on the board: if an emitter releases 0.5 gallons in an hour and a tree has two emitters, the tree receives 1.0 gallons in that hour. Model the decimal placement out loud rather than treating it as obvious.

Independent practice (20 min): Students complete the seven questions on the Student Handout. Circulate and watch for the two errors that show up most often, which are lining up decimal points incorrectly when subtracting 2.4 from 9.5, and multiplying only one emitter's output when a tree has two of them.

Closure and formative check (10 min): Ask students to hold up a thumb for the statement that most of a tree's weight came from the soil, and a flat hand for the statement that most of it came from air and water. If fewer than three quarters of the class shows a flat hand, reread the two weight numbers from questions 6 and 7 together and poll again. Close by asking two students to say in one sentence why drip lines let the orchard grow the same trees with less water.

Tannerly Orchard's Drip Lines: Where a Peach Tree's Mass Comes From — Grade 5 Science
Name: ____________________________ Date: ______________

Student Handout

Tannerly Orchard grows peach trees in long rows. Each tree has 2 drip emitters at its roots.

  1. Each drip emitter puts out 0.4 gallons of water in one hour. Each tree has 2 emitters. How many gallons does one tree get in one hour?
  2. The orchard runs the drip lines for 3 hours. Each of a tree's 2 emitters puts out 0.4 gallons each hour. How many gallons does one tree get in those 3 hours?
  3. One row has 25 trees. Each tree gets 2.4 gallons in one watering. How many gallons does the whole row get?
  4. The block has 4 rows. Each row uses 60 gallons in one watering. How many gallons does the whole block use in one watering?
  5. Before the drip lines, flood watering gave each tree 9.5 gallons in one watering. Drip lines give each tree 2.4 gallons. How many fewer gallons does each tree get now?
  6. A young peach tree weighed 4.5 pounds on the day it was planted. Three years later the same tree weighed 62.5 pounds. How many pounds did the tree gain?
  7. The dry soil in that tree's large pot lost only 0.2 pounds over those same three years, while the tree gained 58 pounds. Explain where most of the tree's new weight came from.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 0.8 gallons. Two emitters each put out 0.4 gallons in one hour, so 0.4 + 0.4 = 0.8 gallons, which is the same as 0.4 x 2.
  2. Answer: 2.4 gallons. One tree gets 0.8 gallons each hour, and 0.8 x 3 = 2.4 gallons over the three hours.
  3. Answer: 60 gallons. Multiply the gallons for one tree by the number of trees: 2.4 x 25 = 60 gallons for the row.
  4. Answer: 240 gallons. Multiply the row amount by the number of rows: 60 x 4 = 240 gallons for the block.
  5. Answer: 7.1 gallons. Subtract the drip amount from the flood amount, lining up the decimal points: 9.5 - 2.4 = 7.1 gallons less for each tree.
  6. Answer: 58 pounds. Subtract the planting weight from the later weight: 62.5 - 4.5 = 58.0 pounds gained.
  7. Answer: Air and water. The soil gave up only 0.2 pounds while the tree gained 58 pounds, so the soil cannot be the source of the new material. The tree took in air and water the whole time it grew, and those two account for nearly all of the gain. Accept any answer that names both air and water and points to the size of the gap between 58 pounds and 0.2 pounds.

Differentiation

Support

Give these students a handout copy with the decimal points already aligned in a vertical format for questions 5 and 6, and let them use a calculator for questions 3 and 4 so the arithmetic does not hide the comparison the lesson is making. Before independent practice, walk them through question 1 aloud.

Extension

Ask these students to find how many drip waterings the block can run before it uses as much water as one flood watering of the same 100 trees, using 9.5 gallons for each tree under the flood method and their answer from question 4 for the drip method. Have them write two sentences explaining what the orchard gives up and what it gains by switching.

ELL supports

Pre-teach emitter, drip line, and gain with a simple labeled sketch showing a tree, a black tube along the ground, and two arrows at the roots. Provide sentence frames for question 7 in the form of a tree that gained a stated number of pounds, soil that lost a much smaller number of pounds, and a closing phrase naming where the new weight came from.

Extensions

Have students weigh a small potted plant together with its dry soil at the start of a month, keep it watered on a schedule they record, and weigh both again four weeks later. Ask them to compare their own two numbers with the Tannerly record and decide whether their result supports the same argument.