Have you ever wondered whether the state of your soil may be affecting your crop or pasture? Allegrow held soil field days in the Edgecumbe and Ōpōtiki areas in March 2024 as part of the Integrated Farm Planning Series. At these field days, soil expert Graham Shepherd from Bioagrinomics guided participants through Visual Soil Assessments (VSA), a simple method of assessing the quality of the soil as well as the plants (e.g. pasture, crop) that are growing in the soil.
Graham describes the soil as the ‘engine room’. If the soil is not in optimum condition, any plant growing in it will struggle to reach its potential. By visually analysing the soil and determining what factors may be hindering it, steps can then be taken to improve soil quality.
A VSA doesn’t require any special equipment and is as simple as digging out a sample of soil and comparing it against specific soil indicators. These soil indicators are described in depth in Graham’s book “Visual Soil Assessment Field Guide[1]”. The indicators include the soil texture, structure, colour and smell. During these soil assessments we also looked at how many mottles and earthworms were present. Other indicators included the potential rooting depth and surface ponding.
When carrying out a VSA, a score is given to each of the indicators by comparing the soil sample against the notes and pictures in the field guide. For example, the number, size and colour of soil mottles indicates how well the soil is drained and aerated. If the VSA determines that the sample has a large number of grey mottles it will be given a low score as this indicates that the soil is likely to have been waterlogged and deprived of oxygen.
Each of the soil indicator scores in the VSA are weighted and then totalled to give an overall score for the soil sample. Soils in poor condition will have a lower total score than those that are good condition which will score highly. VSA’s can be carried out in the same area over time and a comparison to previous scores can be used to monitor soil health.
These field days helped reinforce for participants that knowing the condition of your soil is an important tool in planning for and maximising your crop or pasture.
Sue Clark – Environmental Consultant
[1] Visual Soil Assessment, Volume 1: Field Guide for Cropping & Pastoral Grazing on Flat to Rolling Country, T. Graham Shepherd, Landcare Research 2000