For some reason, many farmers have been led to believe that they need several years of Yield MAPS in order to start a variable-rate program. This is not true. Yield is a valuable layer if it is available, but it is not a critical layer.
With Yield MAPS, we are able to measure the yield potential in the field under a variety of weather conditions. Yield data provides a good knowledge base about the consistency of yields throughout the field. If good data is available we get a good feel for areas that are consistent. Maybe they are consistently poor. Why is this? Maybe they are consistently high. Why are some areas high and some low? Maybe they are high yielding in some years and poor in others.
Generally, with good MAPS data from other sources, we can tell how a field is going to yield anyway. If it is a wet, saline, depression it will likely always be a poor yielding area. Sandy areas may be good in wet years and poor in dry years. Well drained clay loam soils in the midslopes and flats are likely consistent at providing good crops under a variety of conditions. For trials, yield MAPS are extremely nice to have as they are much easier to work with than weigh wagons. As long as the trial is setup correctly, there is really nothing to do.
Yield MAPS are valuable tools if you have them, but not an essential item.