Soil sampling

Why do we soil sample?

application rate of soil amendments in

response to measured soil properties is the underlying principle of Precision Farming

What is found in a soil test?

nutrient levels

• pH

• organic matter content

• soil texture

• cation-exchange capacity

(CEC)

What are the 2 basises of soil sampling? which is prefered?

• grid sampling

• directed sampling

Both are gaining traction

How does grid cell sampling work?

A grid is laid out over a field. samples are collected in each grid and averaged for the area.

How does grid point sampling work?

Each point has multiple samples taken around it and averaged. The map looks a bit more nuances and less like colored grids.

What are problems with the grid method?

differnt soil types get averaged, oddball areas may be left out or overmeasure, local irregularities can drastically change things.

Where do you need to avoid sampling in grid style?

The fertilizer band or measurements will get wicked.

What to do if you do or do not know where the fertilizer band is for sampling?

If known 1. avoid it or 2. sample band porportinally

If unknown, sample randomly and take more cores. 

How to imporve grid sampling?

1. take more samples in high variablity areas

2. use and unaligned grid to introduce more variance

3. use weird paterns like zigzags and wheels

How is directed sampling performed?

Fields are broken into regions that are sampled

What does directed sampling need that grid doesnt?

It need a prior knowledge of zones in the field to create a directed map. 

How do you collect cores in directed sampling?

more cores in variable spots and less in uniform areas.