BackgroundNitrogen fertilizer is an important input for corn production in the upper Midwest. Corn requires nitrogen for adequate growth and grain production. Occasionally, when commercial spreaders apply nitrogen fertilizers, equipment fails and results in non-uniform application patterns. This non-uniformity can cost producers money by reducing yield. Remote sensing can be used to identify potential problems while there is still time for a rescue fertilizer application.

 Use of Data Remote sensing imagery was obtained on 07/05/03 (from Sky Hawk Consulting, Vermillion SD) of a corn field in eastern SD. A vegetative index for the image is shown to the right of the image (Fig. 2). On this scale, more green equals better vegetation.

Examination of the image revealed an area where plant growth appeared poorer than the remainder of the field (outlined by black box, Fig. 2). Especially evident in this area were red patches in the north and south end of this box (Fig. 2). On the south end of the field, areas west and east of the black box in the image show better plant growth as indicated by green. The red patches scattered throughout the strip outlined by the black box suggested a potential problem. Further investigation revealed that 25 acres in this strip received spotty applications of nitrogen fertilizer. The problem was remedied by a rescue application of nitrogen fertilizer.

 Economic and Environmental BenefitsFertilizer or herbicide skips are easy to spot from the road. However, these skips can happen in areas not bounded by roads. As the corn grows in height, nitrogen applications to remedy this problem become more difficult. Also, the later in a growing season that nitrogen is applied to corn, the more growth and potential yield can be lost.

In our example above, hypothetically, we can say that nitrogen application increased yield by 40 Bu/A over the 25 A area. At $2/bu for corn, that equals $2000 additional income. Fertilizer and applications costs $23/A or $625 for 25A strip. Image cost was $160 for field. The potential income gained from the $160 image investment is ($2000 - $160 (image) - $625 (fertilizer)) = $1175.

Remote sensing can provide a quick assessment of field conditions without having to spend the time walking each field. This is important because the total amount of acres farmed by individual producers is steadily increasing. By serving as a guide to problem areas, remotely sensed images can save the farmer time by directing scouting efforts.