It's a tougher decision than usual about how much to fertilise this year, and with what. Most people do not grow pastures like a crop, and so I think it is a correct generalisation to say everyone under-fertilises even when it is relatively cheap.
This year with fertilisers double to triple in price, if you can get any, I see many livestock farmers have decided not to fertilise at all. Perhaps they are thinking that last year was a great year and they cut oodles of hay and silage and will just hang back this year from buying any fertiliser. Perhaps fertiliser will be cheaper by late winter in time for a spring application and cut more hay? I think they are correct about the price falling by spring time, but in the meantime, many are going to have very hungry paddocks.
My philosophy of "pastures first, livestock second" stems from years of watching farmers when I was consulting. They would need to hand feed livestock from about February (summer for Australia) to July (winter). They would spread some superphosphate or superphosphate + potassium in the autumn. To get some hay, they would add extra fertiliser to designated paddocks in early spring.
It always puzzled me though that they saw the extra pasture growth from the extra fertiliser, so why not add extra fertiliser to all paddocks? They could carry more livestock and make more profit, in my view. But by fertilising the pastures better in autumn and winter, they could also greatly reduce the amount of hand feeding they were doing.
What would happen if you applied 200kg/ha of Urea to your pastures at the start of the season? What if you tripled the dose of phosphate and sulphur and potash at the start of the season?
Where we farm, we are fortunate to receive plenty of rainfall. Summers are relatively dry, but every now and then we can have a wet period in summer. With our kikuyu, it is there to use any summer rain, but it goes berserk if there is fertiliser and rainfall.
For most people, the pasture growth from the break of the season to July is the toughest time for livestock. However, you can reduce the pain substantially if you have a perennial in there, or at least drill in barley or oats before the season begins to get more early feed. And importantly, do not graze it until there are more than 2-leaves on the grasses (3 is even better), and fertilise it well. If all nutrients are at good levels and the pH is OK, then nitrogen becomes your best bang for your buck.
If for example the pH is still very low or any other nutrient is lacking, then adding nitrogen will give a poor response, or even no response.
To get better pastures so that you can carry more livestock, make more profit, and reduce the need for hand feeding, you need to fertilise your pastures enough to utilise as much of the rainfall as possible, and remove low pH's ASAP. The principle is to make sure there is plenty of phosphate right at the start to the season, and there is always enough sulphur, potassium and trace elements. Then to get more pasture growth from autumn to winter, add nitrogen around late April to early May. The more you add, the more feed you should produce, and it will be of higher protein. It will usually be much cheaper than hand feeding.
But to get back to this years pricing, should you fertilise to whatever the plants need? It of course depends, but to cut to the chase, livestock prices are also very high. If spending another $100/ha on fertiliser that enabled you to reduce handfeeding by 40%, and you could carry an extra two ewes/ha who produce an extra two lambs/ha, that would be easily worth it.
If all you do is spend more on fertiliser and do not have more livestock to utilise it, then all you have done is increase your costs and reduced your profit. However, most peoples pastures are already starving. Their philosophy is livestock first and pastures second. When there is unused rainfall, this is the wrong way around. You end up concentrating on growing hay and feeding it back to them at the start of the season. I think the hay growing is fine for roughage and insurance, but much more effort needs to go into growing better pastures.
Just for your own interest, go and spread a crazy high rate of a phosphate + S + N + K (if needed) in strips on a few of your pastures. It will be an eye opener if you have not been turning that rainfall into pasture.