Can you still apply nitrogen at current pricing?
One of the major drivers of dairy farm profitability is the consumption of homegrown feed. Before it can be consumed, it obviously has to be grown and nitrogen is frequently a nutrient limiting pasture production. You might recall the theory of Liebig’s barrel that presented the idea that growth will be determined by the most limiting nutrient regardless of how much of the other nutrients there are. Outside of moisture, N is often the cause of under-performance in terms of pasture growth.
The issue this year is that you will need to pay in excess of $1200/t (probably closer to $1600 than $1200) to buy the nitrogen for your homegrown feed. The important thing is that it is used strategically to get the best possible use out of it – rather than just sticking with a recipe or the same old thing that you have always done. The basic rules will remain the same though – apply between 20-50 units of N per application either 3-5 days before or after grazing (rather than blanket application across the whole farm) to supply a minimum of 1 kg N/ha/day (Autumn and Winter) and a maximum of 1.75 kg N/ha/day (Spring). In line with this, if you are going to push towards 50 units of N per application, the best time to do this will be Spring. In comparison, a 20 unit application is best applied during the Autumn and the Winter. During the Autumn if you are not sure whether there is adequate soil moisture available, you might consider using ‘Green’ urea (urease inhibitor treated urea) which will cost $70-90 per tonne of urea more but will help ensure that less is lost to volatilisation (straight up into the atmosphere).
The critical thing is to ensure that moisture isn’t limiting when it is applied so that the response will be a minimum of 15 kg DM pasture growth per kg of N applied. This response rate is normally experienced in Autumn (assuming moisture isn’t limited) and spring (where responses can be as high as 20-25 kg DM pasture growth per kg of N applied). During the winter, the response rate can drop as low as 5 kg pasture dry matter per unit of N applied. This response rate is typically driven by pasture species, soil temperature, waterlogging (don’t apply to paddocks that have surface water) and sunlight but management can also play a part, as well as levels of other nutrients. Whilst a response to N can be observed at soil temperatures as low as 4 degrees, it will not be high enough to justify the price of N this year. This is where the program might have to vary from previous years, depending on how cold, wet, and sunny it is during the winter. You might also try to avoid hot spots in paddocks (ie. Around gateways and water troughs etc..) and this could save up to 20%.
After the pasture response rate, the focus is on utilisation of what has been grown so that you aren’t wasting too much (aiming for 75% utilisation with a maximum achievable level of 8%). If pasture growing costs are higher than normal it is even more important to make sure that it is utilised effectively. This means minimising wastage as much as possible by using supplements to complement the homegrown feed as well as preventing over and under grazing. During the winter in particular it might be important to employ ‘on-off’ grazing strategies where cows are put into a paddock for as long as it takes to reduce the pasture cover to an acceptable residual (1500 kg DM/ha minimum – below this and you will slow the recovery as the plant will have to come back from stored root reserves rather than through photosynthesis in the leaf) and then moved off onto a feedpad or sacrifice area for some other supplement (hay, silage etc..). At the other end, don’t let the canopy close or the ryegrass go past 3 leaves (maximum 3000 kg dry matter per hectare) or you will lose pasture growth.
In terms of the P, K, S, some soil testing to ensure that you are applying only where required would be good. It is a relatively cheap investment to try and save where you can. If you have historically high olsen P’s this is probably a year to not apply much P, apart from some DAP along with the seed (to help get new plants established). K is going to be hard to get and so will come with a hefty price tag. Unfortunately if your soils are lacking K, you will still need to apply it (perhaps potassium sulphate may be an option rather than 2:1 or MOP but it will be dearer) as the plant takes up K on a 1:1 ratio with N. It would also be good to have some S going out through the winter and early part of spring, perhaps by using a blend of urea and ammonium sulphate (50:50).
It will probably be a good year to put out some gibberellic acid too providing you keep the N going. This will really help keep the pasture response up during the winter when the soil temperatures are low and the risk of water-logging is high. Remember if you are going to apply gibberellic acid (plant growth hormone) to push winter pasture growth you will need to have N, P, K and S available in the soil or you won’t see the usual growth response. It doesn’t replace fertiliser – it complements it.
Matt Harms (On-farm Consulting) told a Westvic Dairy farmer workshop recently that if you have 30% legumes (or less) in your pastures, the maximum amount of nitrogen that can be fixed per year by these is around 50 kg per hectare. That is equivalent to 1 application of 100 kg urea per year so the answer to this year’s high fertiliser prices won’t be to add a couple of kg of clover to the pasture mix.
The ultimate message is that for maximum profitability you need to maximise homegrown feed consumption and that is going to require nitrogen application.
The ultimate message is that for maximum profitability you need to maximise homegrown feed consumption and that is going to require nitrogen application. It may be that you vary the rate, type, timing, grazing management etc.. to ensure that can derive enough benefit to justify the application, but the fact remains that you have to do it. Reducing cow numbers or fertiliser levels, or buying in more hay/silage and grain, will not change the fact that you need to get a return per unit of your biggest asset (your land) and that is going to mean maxing out production from it. The only way that your land can pay for itself is for it to grow enough feed for your cows to produce an optimum amount of milk. Then your job is to ensure that it is utilised effectively. It will be a bit more of a challenge to manage nitrogen this year, but the reward will still be there. Fortunately the milk price is also at a record high, so that should help.
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