Soil fertility tips

Home grown feed is the cheapest source of feed. It’s important to make sure pasture growth is not limited by soil fertility. Here are some key tips and focus areas for soil fertility.

1. Get good advice

Ask your adviser for a 4Rs fertiliser plan (Right fertiliser, at the Right rate, at the Right time, and the Right place) and a nutrient budget. The budget will account for the plant nutrients you may be importing on to your farm in feed, as well as identifying other plant nutrients needed to reach your pasture growth goals.

Ideally, look for an adviser with Fertcare accreditation.

2. Get more out of your soil tests

Why soil test?

Without recent soil tests it is almost impossible to get soil fertility right. Soil tests check the status of essential plant nutrients, and identify other soil related issues that can limit pasture growth, for example pH (acidity-alkalinity).

Where should I soil test?

You need a soil test from each group of paddocks with similar soil types and management history. This means breaking the farm up into farm management zones (FMZ)  for fertiliser management.

Big savings can be made by customising fertiliser blend types and rates to suit each FMZ, rather than using blanket applications across the farm.

Start by identifying the FMZs on a map, and then record the soil test results, previous fertiliser/manure applications, silage/hay making, cropping etc. Use this info to target your fertiliser requirements to each FMZ.

How do I collect samples?

Soil testing should be done at the same time of the year, however soil test now if results are more than 2 years old. At least 30 soil cores are required for each sample. Cores should be taken along monitor lines or transects that you can come back and re-sample in 1-2 years, or collected randomly across the area, but in each case taking care to avoid dung and urine patches, areas near gateways, water troughs, and stock camps etc.

Take the samples to the standard depth (7.5cm in Tasmania, 10cm in all other states). Keep the samples cool and send them to a NATA accredited or ASPAC certified soil testing laboratory ASAP. Soil samples should be sent to the same soil testing laboratory each year to ensure consistency.

3. Use Nitrogen fertiliser strategically

Get better results from N fertilisers by using the following tips: 

  • Consider four factors when evaluating the economic value of a N fertiliser application:
  1. Nitrogen fertiliser cost ($/kg of actual N in the product.).
  2. The expected pasture growth response to N fertiliser [kg of dry matter (DM)/kg N applied].
  3. Efficiency of pasture utilisation (by grazing or harvesting) and cost of the pasture consumed ($/t DM).
  4. The cost of nitrogen compared to alternative feeds.
  • Using N to produce feed that can be grazed directly is the most cost-effective option.
  • The response to N fertiliser is related to the underlying growth rate of the pasture; to get a response to N, soil moisture should not be limiting.
  • Appling the equivalent of 1–1.5 kg of N/ha/day of N fertiliser during the growing season is a ‘rule of thumb’ for best pasture growth.
  • Even though pasture growth responses are variable during the yea,r N applications can be profitable even at low response times due to the high cost of other feeds.
  • Check that the nutrients in dairy effluent are being used well. Effluent and manure provide an opportunity to further reduce fertiliser costs.

4. Pasture Consumption on the farm

Calculating how much pasture was consumed on your farm is an important factor when considering the amount of plant nutrients required. Maximising the use of pasture is a cost effective, environmentally responsible and financially viable starting point.