Why do they do that? – Terraces and Tile Lines

Much of Iowa seems flat, but as we’ve previously discussed there is actually a lot of variety to the Iowa landscape. In addition to this, many Iowa farmers dabble in terracing – creating terraces on the slope of a hill. But why do they do that?

Maybe you’ve never even noticed it, but look closely at Iowa fields – especially in the southern half of the state – and you will see terraces on many hillsides.

One thing that Iowa farmers struggle with is soil loss and erosion from water running across the field. When water after a rainstorm flows across the field it can pick up soil particles and carry those particles downstream. Loosing that soil off the field might make the field less fertile. The steeper the slope or grade of the land (like a hillside) the faster the water will move. The faster the water moves, the more soil it might pick up and carry away with it.

Avoca Terraces

Terraces placed on the slope protect the soil from erosion. Photo courtesy of USDA-NRCS, Iowa.

So farmers need to try and slow down the movement of water. Hence, terraces. Terraces are man-made earthen structures that intercept runoff on slopes. They change long slopes into a series of shorter slopes. At each level of the terrace, water has a chance to slow down and the soil has a chance to settle out which keeps it on the field. The result is that cleaner water leaves the field and not as much erosion occurs.

Farmers mound up soil on the hillside creating a somewhat level area with a short steep backslope down to the next level. The top, flat area can still be farmed with crops. The short steep backslopes are seeded with perennial grasses. The roots of these perennial grasses help hold the slope in place.

Sometimes terraces can also include a tile line and drain. In some cases and if there is considerable water build up, farmers can install a tile line and drain. This will allow the soil to settle out and the water to be siphoned off into an underground pipe. This allows the water to run through the pipe down the slope without collecting any soil. The water is discharged at the end of the pipe. This also reduces soil compaction and and enables good root development.

In Iowa, terraces are a fairly common practice. In fact hundreds of miles of terraces help cut soil loss. In one watershed management area terraces reduce soil loss by as much as 13 tons! New terraces might be installed in the fall of the year after growing crops have been harvested or in the spring of the year before crops are planted. In addition to reducing soil erosion, terraces can help retain moisture for growing crops and water conservation purposes. Terraces can even help create nesting habitat in the grassy back slopes that are largely untouched.


Science Education & Agriculture: A Natural Fit


Last August, Iowa adopted the Next Generation Science Standards (NGSS) as the new standards that guide science instruction in schools across the state. Like all standards in the Iowa Core, the new science standards establish statewide expectations for what students learn in a given grade.

The new science standards focus on how students learn, not what they learn.  Local districts, schools and teachers determine their own curriculum, including what is taught throughout the year and how it is taught.   This enables them to choose topics and teaching methods that resonate with their students.  We’ve focused substantial effort during the last year learning about NGSS and developing lessons and professional development opportunities that will help teachers meet the new standards by observing and exploring examples of science phenomena around them.

The need for high-quality science education is essential today.  When current students graduate from high school, more jobs will require skills in science, technology, engineering, and math (STEM) than ever before.  Students need the kind of preparation that gives them the tools and skills necessary to succeed in a continuously changing world.  The new science standards ensure students do not learn about science, but learn how to do science and develop the ability to think critically, analyze information and solve complex problems.  These skills will help today’s students solve tomorrow’s problems relating to healthcare, energy, agriculture, and more.

The agriculture connections in the standards are vast and found in all grade levels.  Kindergartners can explore plant needs by observing vegetable plants in a school garden or growing soybeans on their windowsill.  High school students may design an experiment and analyze data comparing the impact of conservation practices on soil and water quality.

To illustrate the science and engineering applications in agriculture that can be explored in a science classroom, let’s take a look at a few of the 5th grade Next Generation Science Standards.

In the examples below, I’ve highlighted the Performance Expectations (aka standards), as well as the Disciplinary Core Ideas that connect to agriculture.  The Disciplinary Core Ideas provide more detail about the scientific principals students will need to understand in order to “do” what is outlined in the Performance Expectations.    Disciplinary ideas are grouped in four areas: physical science, life science, earth and space science, and engineering, technology and applications of science.

Physical Science

Motion & Stability

There are many examples of gravitational force in agriculture.  A class could identify evidence of gravity on farms and investigate how gravity is utilized when designing equipment and storage facilities (truck trailers, grain bins, hay bailers, etc.).   Or a class could explore gravity’s role in plant growth (Geotropism).  In a simple activity like Topsy Turvy Soybeans, students can observe that roots always grow down and shoots grow up, no matter what way the seed is oriented.


The study of energy conversion lends itself perfect to an investigation into livestock feed its components.   Students can develop models (drawings, diagrams, physical replicas, etc.) represent how the suns’ energy was converted by plants (corn, soybeans, oats, etc.) through photosynthesis into food for a particular animal.

Life Science

Molecules to Organisms

By growing plants and designing investigations where air or water is restricted, students will be able to better understand and describe what happens when and air and water are restricted.   Students can take this beyond the classroom by exploring the importance of water on crops while talking to farmers or researching the effect of drought to particular fruit, vegetable and grain crops.

Earth & Space Science

Earth & Human Activity

This standard is a great opportunity to learn about conservation practices in agriculture and explore how science and technology are to reduce farming’s impact on land and water.

If you can’t tell, we are excited about the new science standards and opportunity they provide for students to learn scientific principles and skills by exploring real-world situations around them – especially those relating to agriculture!   During nine Agriculture in the Classroom Workshops across Iowa this summer, teachers will have the opportunity to learn more about agriculture connections to NGSS by and see the connections first-hand while visiting farms, ethanol plants, equipment dealerships and more.