There is no doubt that one of the biggest challenges inside the dairy farm gate in coming years will be optimising soil fertility. If improving soil fertility wasn’t on your list of to-do items up to now, then get it on your agenda very quickly.

Many farmers are only at the starting line on a journey of discovery to see what quantities of feed they can grow on their farm. Up to now, milk quota has been the most limiting factor on dairy farms, but in coming years it will definitely be how much feed you can grow and how best you utilise it.

Action

The autumn is the best time to take a soil sample so that you can assess the limiting nutrients in your paddocks. By taking the samples now, it gives you a chance to develop a plan for the New Year.

In some paddocks it might not always be nutrients that are limiting – potentially it could be infrastructure or drainage. In these cases, it may pay to fix the farm roadway or fix a drain before it will make sense to apply artificial nutrients. You need to be able to harvest what feed you grow.

It is important to keep a log for each paddock so that you can build up a grass growth record and history for your farm. Take the soil samples yourself and post them off to any of the Deparrtment registered laboratories or get your local consultant to take the samples and look after postage and packaging.

Remember there is no closed period for spreading lime or potassium.

1 Taking the soil sample properly is probably the most important part of the soil-sampling process. This means you need to zig-zag through the area to be sampled. Take samples to 100mm depth. Sampling area should not exceed 4ha. Avoid unusual spots.

2 Package and label the sample properly. Write your paddock number on the bag. You need to have a clear record of what samples are submitted. Ideally, you only need 400g of soil. Specify what you want tested. The majority of samples submitted are tested for Phosphorus (P), Potassium (K) and lime only but you can test for trace minerals if you want.

3 Understand the most limiting nutrient will impact on growth. This means if your P and K is right but the pH is wrong then you need to fix the pH.

4 Lime – the target for grassland paddocks is to reach a soil pH of between 6.2 and 6.5. There are two main ways that lime leaves your farm: (1) Spreading bag nitrogen. Every 100kg of nitrogen needs 200kg of lime to neutralise the acidity; (2) Every year, upwards of 500kg of lime per hectare leaves the farm because it is washed down and away. As a rule of thumb you need to spread 1t of lime per acre per year just to hold the existing pH status.

5 Phosphorus – If soil P index is low then the best advice suggests to front-load the P in the early part of the year so that you improve the availability and maximise the benefit of any bag nitrogen.

6 Value of slurry – Given the rise in the price of fertilizer, the relative value of 1,000 gallons of slurry is now over €20 per 1,000 gallons. That means a 2,500 gallon tanker has €50 of nutrient value in the tank.