Sheep and beef farms have a lower economically optimal Olsen P range of 10-15 on the hills and 15-20 on rolling and flat land. If finance is limited for fertiliser, phosphorus should be applied to crops first followed by new pastures then hay and silage paddocks, flat and rolling land with Olsen P below the target range and hill country below the optimal range.
Sulphur is the cheapest nutrient and is only retained well on volcanic soils so should still be applied at 40-50kg/ha/year on dairy farms and 20-30kg sulphur/ha/year on sheep and beef farms that are not volcanic.
Potassium is also a nutrient easily lost from the soil and that is essential for clover growth. If soil QT potassium levels are in the range of 6-8 then requirements on dairy farms can be halved. In the lower range of 4-5 it still should be applied at full maintenance rates. On all farms hay and silage paddocks should receive 15-20kg potassium a tonne of drymatter (DM) or pasture composition will deteriorate.
Nitrogen fertiliser should only be applied if a feed budget shows there is a deficit in pasture supply. It is still the cheapest form of supplementary feed as long as a 10kg DM/kg nitrogen response is obtained. SustaiN to restrict ammonia losses through volatilisation will still be economic at current product prices.
There is scope to cut back on phosphate for at least one year.
Lime can be omitted for one year with little consequence for pasture production. On hills where lime is flown on the application of potassium and sulphur will always give a better return unless Olsen P is greater than 15 and soil pH less than 5.2.
In hard times information is gold so use your fertiliser consultant and make sure you have good soil test data. In fact especially if the poor payout persists on dairy farms, all-paddock testing if only for Olsen P would be worthwhile to prioritise low-testing paddocks. Always ensure the fertiliser product or mix that gives the lowest cost for each kilogram of nutrient needed has been calculated.
On sheep and beef farms if fertiliser history is sketchy on hill country and Olsen P levels on the low side, shop around for deferred payment terms so fertiliser can be applied in spring to boost pasture growth.
Overall, it’s worth remembering that farming is a long-term strategy and fertiliser is what keeps you in the game.
- Jeff Morton is a scientist and Ballance Agri-Nutrients soil fertility specialist.
