It’s a question we are often asked, ‘Should I aerate, before or after fertilizing? & is it best to aerate before, during or after a drought’. Well, in this blog we’ve put our knowledge along with that of other research together to answer those two questions.
Read on to find out when the best time to aerate is.
Should I aerate before or after applying fertilizer?
No matter whether you apply fertiliser in solid or liquid form, you should always aerate compacted ground prior to spreading fertilizer such as nitrogen etc.
When N is spread over compacted soils, it either leaches down beyond the root zone (as root growth is short & stunted in compacted ground) where it’s forever lost & adds to soil acidification issues. Or if the ground is too compacted it will simply run off the paddock! In both cases you lose valuable fertiliser with no growth benefit.
So to sum this question up, aerate your compacted subsoils prior to applying fertiliser. This enables the fertiliser to get to where it needs to (roots) along with enabling the pasture to respond with deeper root growth where it will utilise nutrients in the lower reaches of your subsoils.
Should I aerate before, during or after drought?
This is another question that’s been asked more frequently of recent times, with dry conditions in the upper North Island, and of course the recent/current drought situation in Australia.
It’s no secret that the subsoil can hold water & moisture even in some of the most dry times, if your pasture root system can access this resource the effects of the dry/drought are lessened to some extent. Otherwise root systems are restricted to the upper top soil layers which are most prone to dry spells, causing pastures to brown off quickly and crops to become less resilient, often leading to an over reliance on irrigation.
Given that subsoils can hold moisture, it’s advisable to ensure soils are aerated in order to maximise the in-soil water storage capacity of the subsoil. This will ensure the effects of any drought will be minimised by the in-soil water storage along with the root system's ability to access it.
Subsoil aerating increases the effective soil depth in which roots can grow & water & nutrients can be held (as explained above). See an excerpt from the United Nations Food & Agriculture Organisation discussion paper below:
“All practices that increase the effective soil depth will result in an increase of in-soil water storage. The effective soil depth may be limited by compacted layers, hardpans or plough pans. By removing these layers, plant roots and soil biota can explore a larger volume of soil and so create favorable conditions for water storage” (FAO Discussion Paper: Drought Resistant Soils)
See the video below of pasture affected by a dry which cannot access subsoil moisture due to underlying compaction issues, causing roots to grow horizontally without vertical penetration into moisture laden subsoil.
So to sum up the answer to this question, it is most ideal to aerate soils prior to drought, however significant benefits can still be realized by aerating during the dry to allow root access to subsoil moisture.
If you want to know more about subsoil aeration & how it helps to increase pasture growth & crop yields, check out our guide: All you need to know about Subsoil Aeration & overcoming compaction
Check out New Zealand's most popular pasture aerator here: 304 Panerazer
1) NZFMRA (Code of Practice for Nutrient Management)
2) FAO (Drought Resistant Soils)