By using GIS technology, ameliorants may be applied more precisely within a block, which may achieve considerable benefits for precision viticulture and entail cost savings.
The application of ameliorants (fertilisers) is traditionally managed at block level. Different soil samples from a block are combined, whereafter the average chemical composition of the specific block is obtained. Depending on the chemical demand and surface, the spreader is calibrated at a fixed application rate for the entire block. In this way the block is fertilised evenly, without taking into account chemical variation within the block.
This method is only effective if the block’s physical and chemical soil composition is homogenous, which is seldom the case, especially in the Western Cape where the soil can differ physically and chemically over very short distances, even within a block.
The correct application of ameliorants is a science which is currently not commonly applied in the wine industry. Automated spreaders are able to vary the application rate using GPS technology and a calculated application template. This template is built within a GIS system once a soil scientist has taken soil samples using a GPS apparatus. The placement of soil samples can be based on soil maps or infrared aerial images that indicate the natural variation within the block.
The fertilisation recommendation is calculated per point and the values interpolated to draw up a fertilisation template. The ameliorant template is used to calculate the total amount of fertiliser to be applied. Subsequently the fertilisation template is sent to the application contractor, who loads it onto his GPS. While the contractor drives up and down with the spreader, the GPS is continuously communicating with the variable applicator to adjust the application according to the template.
A map of the lime recommendation template.
A selective spreader.
Large amounts of ameliorants can be saved since only the correct amounts are applied according to the specific requirements.
The end product is a tract of land where the chemical variation is now much more homogeneous and excessive, as well as insufficient fertilisation is eliminated. In this way yields can be considerably increased, seeing that it is easier to achieve the optimal nutritional status of the soil.
Selective application companies such as Agri-Balance may be contacted to do the spreading.