Cows, Corn and a Creek: Choosing a Buffer for Tamarack Farm

Evaluate plans that protect a farm creek's wildlife and clean water while keeping the farm working.

What buffers did on other farms

Read the passage and Table 1, then answer the questions.

A Creek Through the Pasture

1Tamarack Farm raises corn, soybeans and a herd of 60 beef cattle on rolling land in Iowa. Brushy Creek flows for 1,000 m through the farm, with a cornfield on one bank and a pasture on the other. The cattle wade into the creek to drink and cool off, and the corn is planted almost to the edge of the bank. Brushy Creek flows into Lake Corwin, which supplies drinking water for the town of Corwin and is a popular place to fish. Seventh grader Joaquín Herrera, whose family owns the farm, helped the county conservation district study the creek for a school project.

2When rain falls on a field, water running off the surface can carry soil and fertilizer into a creek. Soil clouds the water and can bury the gravel where many stream insects live. Nitrate, a form of nitrogen found in fertilizer and manure, can feed large growths of algae downstream, and water treatment plants must remove it when drinking water holds too much. Strips of plants along a creek, called buffers, slow runoff and take up some of the nitrate. Their roots help hold the banks in place, and taller plants shade the water and give birds places to nest.

3The conservation district had already tested three kinds of creek stretches on nearby farms with similar soil. Water samples were taken after the same storm (Table 1).

4The district offered Joaquín's family five plans (Table 2). Plan 5 puts a 30 m strip of trees and shrubs on the cornfield bank and a 10 m grass strip on the pasture bank. The family set two limits: the farm can pay at most $25,000 to build the plan, and it can give up at most 5 hectares (ha) of cropland and pasture. The watershed group that manages Lake Corwin set two goals for the creek below the farm: nitrate of 5 mg/L or less, and at least 13 kinds of stream insects. The family loses about $600 of income each year for every hectare taken out of crops or pasture.

Table 1. Pilot Stretches on Nearby Farms (strips on both banks)
Stretch	Nitrate below (mg/L)	Sediment, storm (mg/L)	Stream insect kinds	Bird species, June
A: Cattle in creek, crops to the bank	9.0	240	6	8
B: Fenced, 10 m grass strips	6.0	90	11	12
C: Fenced, 30 m trees and shrubs	3.5	40	17	23

After the storm, the water below stretch A carried times as much sediment as the water below stretch C.

Which pattern does Table 1 show from stretch A to stretch C?

A. Nitrate and sediment went down, while insect kinds and bird species went up.
B. Nitrate and sediment went up, while insect kinds and bird species went down.
C. Bird species went up, while insect kinds went down because birds ate them.
D. Nitrate went down, but sediment, insect kinds and bird species stayed about the same.

Use paragraph 2. Why did the water below stretch B carry much less sediment than the water below stretch A?

A. The fence kept cattle off the banks, and the grass slowed runoff from the field.
B. Stretch B got less rain during the storm, so less runoff reached its creek.
C. The fence kept cattle from drinking, so the creek held more water to thin the mud.
D. Stretch B had more kinds of stream insects, and the insects ate the sediment.

Which result from Table 1 best shows that a wide strip of trees and shrubs supports more kinds of living things beside the creek than a grass strip?

A. Nitrate below the stretch fell from 6.0 mg/L at B to 3.5 mg/L at C.
B. Both stretch B and stretch C kept the cattle out with a fence.
C. Bird species seen in June rose from 12 at B to 23 at C.
D. Sediment after the storm fell from 90 mg/L at B to 40 mg/L at C.

Five plans for Brushy Creek

Use Table 2 and paragraph 4.

Table 2. District Estimates for Brushy Creek (1,000 m of creek on the farm)
Plan	Build cost ($)	Land taken (ha)	Nitrate below (mg/L)	Stream insect kinds
1: Do nothing	0	0	9.0	6
2: Fence and water tank	14,000	0	7.5	9
3: Fence, tank, 10 m grass on both banks	18,000	?	6.0	11
4: Fence, tank, 30 m trees on both banks	30,000	?	3.5	17
5: Fence, tank, 30 m trees, 10 m grass	24,000	?	4.5	15

Land taken = 1,000 m of creek × the strip width on each bank, added for both banks. 1 ha = 10,000 m².

Plan 3 takes ha, Plan 4 takes ha, and Plan 5 takes ha.

Which plan is the only one that meets both goals and stays within both limits in paragraph 4?

A. Plan 2
B. Plan 5
C. Plan 4
D. Plan 3

If the family chooses Plan 5, it will lose about $ of income each year from the land taken.

Compared with Plan 4, what is the main trade-off of Plan 5?

A. It takes more land but costs less, and it leaves the same nitrate as Plan 4.
B. It costs more and takes more land, but it leaves less nitrate and supports more insect kinds.
C. It leaves less nitrate than Plan 4, but it supports fewer kinds of stream insects.
D. It costs less and takes less land, but it leaves more nitrate and supports fewer insect kinds.

The family shows Plan 5 to people with different concerns. Match each person to the part of Plan 5 that answers that concern best.

A town water manager worried about nitrate in Lake Corwin
The family, worried about losing too much farmland
An angler who wants more food for the fish in the creek
A cattle owner worried the herd will lose its drinking water

A. Only 4 ha are taken out of crops and pasture.
B. Nitrate below the farm drops from 9.0 to 4.5 mg/L.
C. Stream insect kinds rise from 6 to 15.
D. A water tank is set up in the pasture.

10.

A neighbor says, “Plan 2 is good enough. Fencing the cattle out is the cheapest real fix, and it takes no land.” Do you agree? Write a claim, use evidence from Tables 1 and 2 and the goals and limits in paragraph 4, and explain how your choice affects biodiversity and the services the creek gives people.