Taking representative soil samples

The main causes of variability are: *
Temporal variation applies to when the sampling was done *
Spatial variation refers to how much of a paddock is sampled *
In cropping, the usual test depth for soil sampling is *
EM maps and NDVI maps can help determine sampling areas *
EM maps and NDVI maps of the same crop look the same, but measure different things *
How many cores should be taken to get a representative sample for soil testing? *
Which of the following areas should be avoided when taking soil samples for nutrient testing? *
Which map or maps might give most helpful information about the need for side-dressing in different parts of a crop? *
Fertiliser applied "down the spout" at planting causes an extra complication for soil sampling *
If banded fertiliser is on about 1/5th of a bed, how many cores should be taken in that zone? *
For which nutrient is it useful to sample the whole root depth rather than the standard depth? *
A maize crop is better than lettuce to scavenge nitrogen from deep in the soil *