Traditionally, one set of soil samples is taken in the field and the target pH is set artificially high to reduce the risk of areas being at or below the yield limiting soil pH levels. However, now that we have the technology that can take more samples per hectare, we can afford to set the pH at what it should be. This could save up to 2 tonnes of lime per hectare. The low pH areas will immediately be brought up to target pH, and the high areas will not receive too much lime.
This image shows how the trace element availability changes with increasing pH. The target pH that we recommend is between 6.2-6.4 because this is where most elements are readily available.
pH variation can be mapped by taking soil samples on either a grid or zone basis. For mapping pH and lime we would recommend grid based sampling. We have found through years of experience that pH variation is caused by three factors:
1. changing old field boundaries - where fields have been amalgamated, cropping and lime application history is still evident years after.
2. soil texture - for example, in sandy areas the pH tends to drop quicker than heavier areas.
3. spreader and lime application mistakes - this is a major source of pH variation. Lime can get dumped in gateways or there could be mistakes made with the calibration of the spreader.
These factors create large long lasting variations in pH that cannot be detected in any way, other than soil sampling.
FarmWorks Site software can be used to make the lime application maps. Soilessentials also provide a service whereby we can create the application maps for you.
To learn more about our mapping service, click HERE.