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Know Your Earth 2.0: Agriculture
 
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Every day, people use NASA satellites to help put food and water on the table.

Ultimately, all of our food comes from plants. NASA's Aqua, Terra, and Landsat satellites track plant growth by measuring how much light plants absorb during photosynthesis. These measurements can reveal what is growing and how healthy the plants are. When scientists compare current plant growth to average growth, they can detect drought or a bumper crop. Farmers use the information to manage their fields of wheat, corn, soy and more. Relief agencies use the measurements to detect food shortages before a famine develops.

The Upper Midwest Aerospace Consortium has provided farmers with tools using Landsat and other satellite sensors to help them manage croplands. Using these tools, farmers can quantify crop damage due to weather events or stray chemical treatments, determine where to apply more or less fertilizer, and target what areas need more or less irrigation, better than they could do using their own eyes alone.

One example of how farmers use satellite data comes from a farmer in Minnesota. After heavy rain events in late July 2002, some of the farmer’s navy bean fields were severely damaged by flooding. The wet conditions also created a favorable environment for white mold infestation. To minimize further crop losses from white mold, the farmer decided to preventively apply fungicide. However, he did not want to waste money spent on fungicide by spraying field areas already irreversibly damaged by flooding. He used remote sensing to observe and map the areas for treatment. Doing this in person would be time consuming and costly.

The farmer used a Landsat infrared image to reveal the areas of flood damaged crops. Based upon this information he created a fungicide spray map to target the fungicide application, avoiding the areas where crops were lost from flooding. By not applying fungicide in the areas in which it was not necessary, the farmer saved nearly $972.00 and reduced the amount of chemicals introduced into the environment.

On a broader scale, the Famine Early Warning System Network (FEWS Net) routinely uses NASA satellite data to monitor the health of growing crops in developing countries. When crops are growing poorly, they are less green and absorb less light during photosynthesis than healthy plants. Those are differences that sensors on the Aqua and Terra satellites can see. In late 2010, for example, NASA satellites detected poor plant growth in East Africa, especially Somalia.

FEWS Net used this information about poor plant growth to issue a warning to governments and aid agencies that East Africa would likely need assistance in the coming year, giving these organizations time to marshal supplies before famine developed. In July 2011, food supplies fell short as predicted, and the United Nations was able to help thousands of Somali people with great efficiency and at less expense than would have been possible without the NASA satellite data.

NASA satellites also provide important information about our global water supply and how we use water to produce food. Landsat takes a field's temperature to determine how much water an irrigated crop is using. NASA's GRACE satellites measure variations in Earth's gravity to detect how water supplies are changing.

Related Imagery

Farms: Each pixel in a Landsat image is a 30 meter square (about 100 feet by 100 feet). To see the condition of his crops in each 30 meter square of farmland, a farmer zoomed in on a false-color Landsat image. Blue-green pixels correspond to drowned-out crop areas, and red pixels indicate crops not damaged by water. The farmer used this map to determine which areas of the crops would merit fungicide application. http://www.umac.org/agriculture/ss/UsingImageryforFungicideApplication/detail.html

Changing water supply: These maps show changes in water storage in the Western Hemisphere from July 2009 through June 2010; that is, they show how much more or less water is tied up in lakes and rivers, groundwater aquifers, soil moisture, snow, and glaciers. The measurements were made by the Gravity Recovery and Climate Experiment (GRACE), twin satellites that measure subtle changes in Earth's gravity field over time. In this case, the satellites measured how Earth's gravity changed as water piled up or was depleted from different regions at different times of year. http://earthobservatory.nasa.gov/IOTD/view.php?id=46472

Managing Water Resources: Because satellites see a wide area at once, they are ideal tools for monitoring evapotranspiration. Evapotranspiration refers to the conversion of water into water vapor by the dual process of evaporation from the soil and transpiration (the escape of water though plant’s leaves). For vegetated land, evapotranspiration is synonymous with water consumption. http://earthobservatory.nasa.gov/IOTD/view.php?id=42428

Global Plant Growth: This image shows plant growth (net primary productivity) in August, when the Northern Hemisphere reaches its peak productivity. Productive plants store carbon. On land, areas where plants are growing most—and storing the most carbon—are dark green. Highly productive areas in the ocean, where the most phytoplankton are growing, are dark blue. Because the bulk of Earth’s land is in the Northern Hemisphere, August is also when global net primary productivity reaches a peak. http://earthobservatory.nasa.gov/IOTD/view.php?id=51289

Additional Resources

› Water Watchers documents how Landsat is being used to monitor agricultural water use.
› GRACE water storage anomaly
› Precious Resources: Water & Landsat's Thermal Band
› How ground water supplies are changing in California

Multimedia:

› Science for a Hungry World
› Famine Early Warning (MP3)
› Podcast: How Landsat is helping people to monitor water use from space
› Landsat: A Space Age Water Gauge