VSA Analysis on Pasture Trial

EMNZ conducted a Visual Soil Assessment (VSA) analysis on a trial plot that had completed a pastoral trial looking at Nitrogen applications with and without EM.

What is a Visual Soil Assessment?

VSA is a method of assessing the health and quality of a soil. Doing a VSA will give an effective assessment of the condition of the soil and therefore the performance of the pasture or crop. VSA is based on the visual scoring of key bio-physical indicators of soil quality. The indicators used were:

  • Soil Structure = is very important on a whole heap of levels including aeration, water holding capacity, root penetration, nutrient holding and supply and many others. It was measure on a scale of 2= Good, 1 = Moderate and 0 = poor condition
  • Soil Smell = A good indicator of the activity of soil life and therefore soil health. It was measure on a scale of 2= Good, 1 = Moderate and 0 = poor condition
  • Root Depth = the depth of soil that roots can potentially exploit before reaching a barrier to root growth. It was measure on a scale of 2= Good - >800mm depth, 1.5 = Moderately Good - 600-800mm, 1 = Moderate – 400-600mm, 0.5 = Moderately poor – 200-400mm and 0 = Poor condition - <200mm
  • Soil Colour = A darker coloured soil generally indicates a higher level of organic matter and humus. It was measure ona scale of 2= Good, 1 = Moderate and 0 = poor condition
  • Soil Porosity = Looks at the movement of air and water in the soil. It was measured on a scale of 2= Good, 1 = Moderate and 0 = poor condition.
  • Earthworm numbers = a straight count of earth worm numbers detected in a spade full
  • Brix Readings = Brix gives farmers a simple tool to measure whether the plant is properly nourished. Brix is a great measurement of pasture quality

Results of the VSA

The technique used was to take a spade square sample from three reps for the control treatments and 3 reps from the EM treatments. For the brix readings I took 3 readings per sample plot.

The results of the VSA provided significant evidence that the EM treated plots were of a much better quality that the non EM plots.

The soil structure was immediately noticeable as better on the EM treated plots with more friable aggregates and more soil crumbs clinging to roots. The smell was pretty good on all of the plots but was excellent on 2 of the EM treated plots. One of the biggest differences was the colour; the EM treated plots had a darker looking soil showing the benefits of the additional organic matter breakdown and microbial activity. The roots also tended to be longer on the EM treated plots. A good example of this is the below picture:

In this picture the EM plot has darker soil. You can also see more fibrous roots and a better crumb structure.

In addition there were more worms in the EM treated plots although these were still lower than what we would have like to have seen. Another very intriguing element was that the brix was significantly higher in all of the EM plots with the average reading being 2 points higher.


Overall we were really happy with the results of this VSA, this is a great indicator of soil quality and has shown EM has a positive impact on the soil ecosystem.