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Remote sensing to determine corn grain moisture Year: 2004 Application Area: Agriculture BackgroundHarvesting wet corn costs money. Many growers harvest grain from the end rows first, check the moisture content and make a decision to proceed or move to a different field. Grain harvested from the end rows often has a moisture content that is different from the rest of the field. Space or aerial platform based remote sensing can be used to check crop maturity levels and identify the driest areas of the field. Use of DataIKONOS and LANDSAT imagery and yield monitor data was collected for a number of fields in South Dakota between 2000 and 2003. The imagery was used to develop false color images and reflectance maps from individual bands. The example used here was IKONOS imagery from August 24th, 2001. False color images were prepared using IKONOS bands 4 (near infrared), 2 (red) and 1 (blue) for 3 corn fields (Figure 1 - left). Corn moisture maps were prepared from yield monitor data of these same fields (Figure 1 - right). Economic and Environmental BenefitsCorn located in toeslope areas typically has higher moisture content and yields than corn located in summit / shoulder area. Remote sensing data collected by both LANDSAT and IKONOS satellites can be used to identify areas with different moisture contents. However, due to resolution differences, IKONOS images look sharper than LANDSAT images. Identifying fields with high moisture corn content saves money. Harvesting grains from a 160 A field that averages 120 Bu/A at 20% moisture will cost $2138 in liquid propane (LP) to dry to 15.5%. However, just waiting for the grain to dry in the field only 2% to 18% will save $950 (Table 1). If management practices are such that low moisture field areas can be harvested first and the higher moisture areas later then savings can also be gained.
Table 1. Estimated cost of LP to dry grain at various moistures to storage moisture of 15.5%. Assumptions: 3500 BTU to remove 1 lb of water; 92,000 BTU / Gallon LP gas; $0.929/ Gallon LP gas; 80% efficiency. Capital costs not factored in, estimate this to be $0.04 / bu, however will vary depending on storage system and is only an estimate.
Table 2. Cost to dry grain in fields shown in Fig. 1 at 20% and 18% moisture using drying costs from Table 1. For example, if our fields shown in Fig 1 could have been selectively harvested, 44, 59 and 24 acres, respectively, had 20% or higher grain moisture (Table 2). Therefore, assuming grain moisture for all acres was 20% (and some was higher) and average yield was 120 bu/A, LP drying costs would be approximately $1697 (Table 2). If the dryer grain areas are removed first allowing wet areas to field dry to 18% for example, LP cost is reduced to $943 resulting in savings of $754. Ability to identify higher corn moisture benefits the environment in that less LP gas is used for drying the crop thus reducing fossil fuel consumption, and saving money. |
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   Figure 1) (Left) IKONOS satellite imagery collected on August 24th, 2001 for three fields in eastern South Dakota. (Right) Yield monitor corn moisture maps collected in October 2001 from these fields.  Figure 2) Scale for grain moisture maps shown in Figure 1. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
