Nutrient Budgeting

Nutrient budgeting is about achieving the full potential of the nutrients needed for pastures and crops to limit fertiliser costs. It is essential to running a cost effective farm business.

Soil testing

Responsible nutrient planning involves soil testing and nutrient budgeting to help identify and then match the nutrients needed with those being applied.

A nutrient budget will account for imported plant nutrients, which may be imported in feed. It also helps identify other plant nutrients needed to reach pasture growth goals. Benefits include financial savings, increased productivity and less nutrients lost to the environment.

It is impossible to fully understand soil fertility without up-to-date soil tests. This kind of testing checks the status of essential plant nutrients and identifies other soil related issues, which can limit pasture growth, such as pH or soil acidity and alkalinity.

A soil test from each group of paddocks with similar soil types and management history, provides the best available information. Consider breaking up your farm into management zones based on soil type or historical fertiliser application to tailor fertiliser application to the relevant zone. Big savings can be made by customising fertiliser blend types and rates to suit each zone, rather than using blanket applications across the farm.

Soil testing should be conducted at the same time each year, or as soon as possible if the results are more than two years old. At least 30 soil cores are required for each sample. Cores should be taken along monitor lines or transects that can be re-sampled every one to two years or collected randomly across the area. Take care to avoid dung and urine patches, areas near gateways, water troughs and stock camps when sampling.

Take the samples to the standard depth (7.5 centimetres in Tasmania, 10 centimetres in all other states). Keep the samples cool and send them to a National Association of Testing Authorities-accredited or Australasian Soil and Plant Analysis Council-certified soil testing laboratory as soon as possible. Ensure consistency by sending samples to the same lab each year.

Nutrient mapping

Nutrient mapping converts soil test results into a visual representation of fertility across the farm. This helps with assessing variability across the paddocks on the farm. Colours are assigned to areas or paddocks depending on whether the nutrient level is low, marginal, good, or excessive. Using nutrient mapping will provide a visual snapshot of the variability across the farm, and areas with excessive nutrient levels, where consideration must be given to reducing inputs.

It is important to identify the farm management zones on a map, before recording soil test results, previous fertiliser and manure applications, silage or hay making and cropping. This information should be used to target fertiliser requirements to each farm management zone.