Each year satellite imagery and ground truthing are combined to create a geospatial data layer that reveal which crop was grown on each field throughout the United States. This annual United States Department of Agriculture National Agricultural Statistics Service (USDA-NASS) analysis and resulting map is called the Cropland Data Layer (CDL). The CDL provides an estimated acreage of each major crop.
The online interface to view the CDL is called CropScape (https://nassgeodata.gmu.edu/CropScape/). For Saline, Jefferson, and Gage counties, imagery is available on CropScape from 2001 through 2020. The 2020 CDL was released online on February 1, 2021. Full coverage of the continental United States started in 2008. The quality of the imagery has improved over time and is now analyzed on a 30-meter (almost 100 feet by 100 feet) resolution. There are four additional data layers created called crop frequency layers for corn, soybeans, wheat, and cotton. A crop frequency layer shows the number of years a specific crop was grown in a field between 2008 to 2020.
There are several analysis tools in CropScape that are useful to agronomists, farmers, and others involved in production agriculture in Saline, Jefferson, and Gage counties. The area of interest tool and area of interest statistics tool allows someone to determine the estimated number of crop-specific acres in a county. For example, the 2020 Saline County estimated acres of the major crops were the following: 153,160 corn acres, 113,336 soybean acres, 5,796 alfalfa acres, and 1,635 winter wheat acres. However, the 2010 Saline County estimated acres of the major crops were the following: 129,762 corn acres, 91,487 soybean acres, 3,399 alfalfa acres, and 7,910 winter wheat acres. Over the last 10 years the increase in corn, soybeans, and alfalfa acres was about 48,000 acres and the decrease in winter wheat and pasture was about 56,000 acres. Looking at the crop frequency layers; continuous corn acres are mostly located in the northern quarter of Saline County where there are nearly level irrigated fields. However, most of the winter wheat acres and higher frequency of wheat in the crop rotation occur in the Loveland Hills of Saline County (Loveland Hills – located south and west of the Turkey Creek where soils formed from Peorian loess, Loveland loess, and glacial till). These trends are not surprising to me or local farmers but shows the value of CropScape in tracking shifts in acres between crops over time and helps verify regional specific crop rotation differences.
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CropScape has been useful when clients call me with questions like “I am looking at putting a cash rent bid on some ground around the airport, how many years has it been planted to soybeans?” or “I consistently notice that part of this new farm (160-acre tract) yields better, any ideas why?” Nebraska Extension recently hosted the inaugural Southeast Nebraska Alfalfa & Wheat Expo in Crete on September 2. So, I wanted to know the average length of time area farmers kept an alfalfa stand. Using CropScape, I could determine by looking at the year-by-year imagery that most alfalfa fields were kept from 4 to 7 years before being planted to another crop. I encourage you to check out CropScape for yourself or schedule an appointment with me if you need assistance in navigating the website.
For more information about using CropScape and other general inquiries about agronomic resources from Nebraska Extension, feel free to contact me at email@example.com or 402-821-1722. Know your crop, know your tech, know your bottom line at croptechcafe.org.