Farmers are looking for reliable evidence that spend on lime and fertilisers is addressing acidity and nutrient availability.
Increasingly, NDVI and yield maps are being used to design management zones for surface soil properties. 28 paddocks across 6 properties were selected for a recent study by Brigette Snell (Monash Uni) and Dr Kirsten Barlow
The majority of paddocks exhibited one or more production limiting soil properties but correlations were hard to establish e.g where acidity was detected these same zones were not the same as where phosphorus was limiting.
Using NDVI there was a general difficulty in creating management zones for different soil properties as they don’t align. Furthermore, low NDVI areas were not located in similar spots each year and the correlation between consecutive layers of NDVI was poor
in over 90% of paddocks, NDVI-derived management zones did not identify soil constraints or provide insight into the factors creating paddock variation
In conclusion, NDVI and yield data as a basis for soil management does not work in broadacre cropping systems. Grid soil mapping clearly provides the most accurate and reliable evidence base for VR management of surface soil properties.