Gathering paddock map information
Gathering good paddock map information is the key to successful variable rate applications.
We can help you gather paddock information from a number of different paddock mapping sources. When these maps are layered over one another, they help us to define zones within the paddock.
Harvest yield maps.
Harvest yield data is generally the best information to gather. The data from the yield maps of previous harvests can be layered when defining zones and accounts for seasonal variability.
The use of airborne imagery has typically been limited because of the high cost involved, but it does have advantages in being able to reliably gather an image at a pre-designated time. Aerial imagery can give more finite detail than commonly used satellites, with resolution down to 50 centimetres. And with the cost per hectare coming down, we’re predicting that airborne imagery will become much more cost-effective in the future.
Images obtained remotely via satellites can be used to identify the variability in crop growth caused by factors such as nutrient deficiencies, disease, moisture stress, weed infestation, insect damage and weather damage. Satellites can often see what we can’t and have the ability to take images of large swaths of land when there are cloud free conditions. We have access to a number of satellites that can deliver information in a range of formats. Commonly measuring red and near infrared reflectance, a satellite image can produce a map of Normalised Differential Vegetative Index (NDVI), which can give clear pointers to parts of a crop that are stressed and parts that are healthy. These zones can then be managed on a specific basis with the variable rate application of chemicals such as nitrogen.
Electromagnetic (EM38) soil surveys.
Electromagnetic soil surveys measure the apparent electrical conductivity (ECa) of soil. Factors such as soil moisture content, salt levels and soil texture can affect the ECa and ultimately, the crop yield. So we measure the ECa through high-resolution EM 38 surveys that involve attaching an electromagnetic sensor to a vehicle and running it across a paddock.
Elevation (topographic) maps.
Using elevation information from yield maps or other digital sources, we can create a topographic map of the paddock. In certain regions, such as the vast dune-swale system in the South Australian and Victorian mallee, paddock topography is often associated with different soil types. In other areas a topographic map can define areas that are more prone to wind and water erosion.
Active in-crop sensors.
Active in-crop sensors such as the Crop Circle™ and GreenSeeker™, are devices that can be mounted to a vehicle and used to create a Normalised Differential Vegetative Index (NDVI) map of a field, similar to satellite imagery. The big advantage of these devices is that they have their own light source (that’s why they have ‘active’ in their name) and can function day or night, or in overcast conditions. NDVI maps created with units like the GreenSeeker™, are commonly used for variable rate nitrogen application. The Landmark Product Development Group has been using GreenSeeker™ technology for a number of years now and has a good understanding of the technology.