From soil to satellite:
Using Landsat data for irrigation By Emery Silberman
Bowles Farming Company in the Central Valley of California, has been using Landsat technology to help make operational decisions since 2000. As the name implies (land + satellite), Landsat is the NASA program acquiring satellite imagery of the Earth, which is free and readily available. In the past, Bowles Farming has primarily used Landsat imagery to monitor poor performing areas on the farm and for variable rate growth regulator applications in cotton. With advancements in satellite data processing technology and the availability of a suite of additional layers of data, we are also able to use Landsat to help make better decisions related to irrigation practices.
Bowles Farming Company is a family- owned and -operated farming operation producing tomatoes, melons, extra- long staple cotton, alfalfa and more. The company uses Landsat imagery to identify consistent homogeneous behaviors in fields and correlate those behaviors to other layers of data being collected. Whenever any operation is done on the farm, each activity is recorded into a central database. This database acts as a checklist for everything that has been done. Due to Landsat passing over every nine days, the imagery acts somewhat as a report card. To refine the control of the farm, we can compare the recorded activities in the database to the imagery collected. This revolutionary technology allows us to better understand the impact of each activity and how it relates to the growth of a crop.
Soil evaluation through a satellite
A crop’s growth is dependent on many factors, and technology has allowed us to examine more and more of these factors. One of the most important aspects affecting a plant is the soil that it grows in. Soil sampling is commonly done to provide growers an in-depth look at what they are growing their plants in. At Bowles Farming Company, we have a device to measure and record the pH, electrical conductivity [EC], and organic matter [OM]. This device not only takes these measurements but it also records the location of the sample. When pulled behind a tractor, this allows us to make maps of the pH, EC and OM.
Using these maps, we can actually apply certain amendments to correct any problematic areas. Traditionally these amendments are applied at the same rate throughout a field, however, this leads to wasted material and can make problematic areas worse. With the knowledge of a pH, EC and OM map, the field can be split into categories based on what is needed. These maps usually have three to four regions where different rates
are assigned. This system allows tailoring an application to the needs of a field.
Because the water-holding capacity of a soil is significantly impacted by the organic matter in it, one of our primary focuses in soil remediation is compost applications. Areas with lower organic matter are given applications of significant amounts of green waste compost to help improve water-holding capacity. Over time, this activity will improve the distribution uniformity of furrow and flood-irrigated crops.
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Utilizing the satellite report card
All of this work related to soil evaluation and remediation is meant to make the entire field grow at the same rate. The best way to keep track of this growth
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This shows a satellite image after variable rate compost applications have been made. The applications are represented by the darker areas.
16 Irrigation TODAY | January 2018
NEW YEAR, NEW TECHNOLOGIES
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