Ryegrass planting options considering fertiliser and fuel supply

Two of the most important inputs on dairy farms are urea and diesel.

To minimise the impacts of uncertain supply and substantial increases in these costs, dairy farmers sowing ryegrass pastures should consider the following options alongside their own unique position. 

Ryegrass planting and fertiliser options

It is important to understand what level of production you require as well as the cost of not producing.

For ryegrass establishment and management, there are 4 main options to consider:

• limit ryegrass pasture to the most fertile paddocks only
• oversow summer pasture with ryegrass but don't apply urea
• reduce urea application
• continue with recommended rate of urea application. 

These options are explored below along with practical considerations around grazing management, paddock selection, nitrogen efficiency, seeding rates and alternative pasture systems.

Option 1: Restrict ryegrass to the most fertile paddocks

If urea became unavailable at any price, dairy farmers may have few options other than a choice between not growing ryegrass or restricting the area sown to the most fertile paddocks. 

In this situation, there will be a shortfall of feed from pasture which will need to be filled through bought-in feed (concentrates or hay and silage).  

The economic implications of buying in more feed to replace a shortfall in ryegrass pasture is shown below.  

The average prices for prepared rations of grain and hay (based on the North Coast region as of April 2026) are:

• Grain - 1 tonne at $600 landed = $0.67/kg DM + feed out costs.
• Hay - 1 tonne $600 landed = $0.69/kg DM + feed out costs.

The table below shows the cost of ryegrass with different seasonal rates of nitrogen and the impact that yield and utilisation have on cost. 

The yields presented are total growth of ryegrass for the season based on expected growth rates in Northern NSW. The costs shown factor in the utilisation % (proportion of growth eaten by the cows). For example, if you grow 7,000 kg DM/ha of ryegrass and utilise 70% of it, then cows have eaten 4,900 kg/DM/ha for the season (which is about average).

If urea continues to increase in price

The table below shows the impact on cost of ryegrass feed produced including volatilisation of urea increasing from $1,500/t to $2,000/t.

Option 2: Oversow with ryegrass but don’t apply urea

The option to oversow summer grasses with ryegrass and not apply urea is not considered viable. 

Yields would be less than half those shown in the table above, and the ryegrass would be low in protein.

This would require an increase to the amount of bought-in feed with a higher protein content. 

Option 3: Reduce the rate of urea application 

For well-managed ryegrass, each 1 kg of nitrogen applied as urea results in an increase to growth of about 20 kg DM/ha. 

This increase in growth continues in a linear way up to a certain point, after which the response declines. From this point, it is no longer economical to apply more urea. Historically, this point was at application rate of 100 kg urea/ha (46 kg N/ha) after each grazing. 

With the increasing price of urea, reducing the rate of application to 70-75 kg/ha is a logical way to balance the growth response and high urea cost.

Keep in mind that any yield shortfall would have to be made up by buying in more feed as outlined above. 

Option 4: Continue with the recommended rate of urea application

As shown in the calculations in the tables above, even at a urea price of $2,000/t, and a worst-case volatilisation cost, the cost of the resultant ryegrass grown would be about half that of bought-in feed. 

Ryegrass still produces relatively cheap feed at approximately $200-$300 t/DM, even at high fuel ($3.30/L) and fertiliser costs (urea $1,500-$2,000/t).  

Increasing the efficiency of urea application

If the decision is to reduce urea application, or continue with the recommended rates, then maximising efficiency will also maximise financial returns. 

The following factors will have the most impact on maximising urea.

Grazing management

Grazing management is one of the most important factors determining the effectiveness of applying urea to ryegrass pastures.

The recommendation is to graze ryegrass after a minimum of 2 new leaves have regrown/tiller since the last grazing. This will ensure that the plant has had enough time to build up reserves for normal regrowth after the next grazing. This is about 20 days in winter (May to July) on the North Coast of NSW. 

Delaying grazing to 3 new leaves will maximise yield. This will be about 28-32 days in winter, and 12-16 days in spring.

Leaving a residue, post grazing of 5-7 cm will optimise pasture utilised. Preventing back-grazing with a ‘back fence’ is also essential to assist plant recovery. 

Select high fertility paddocks 

Sow ryegrass and apply urea to the better or best paddocks – those where responses to urea application are likely to be good. 

These are paddocks with high fertility, with sufficient pH, and other key nutrients including phosphorus, sulphur and potassium.  

Sowing method and preparation

Ryegrass can be direct drilled or broadcast into summer grass pastures. Broadcast seed is usually about 6 to 7 times quicker to sow, which saves on diesel costs and time.

Pasture establishment is similar with both methods unless conditions are dry, in which case direct drilling is often better.  

When broadcasting, it is more important to ensure stock can remove as much of the summer grass in grazings before planting as additional mulcher or slasher passes can result in costs similar to direct drill sowing.

Although diesel is expensive at around $3.30/L, in the context of sowing ryegrass it is still one of the lower cost inputs per hectare. Poor paddock preparation to save fuel could be far more costly in the case of poor establishment.  

Minimising the loss of N through volatilisation

After applying urea, volatilisation (the loss of nitrogen to the air in gas form) is greatest in the first 48 hours. Irrigation, or over 5mm of rainfall, straight after application will reduce N loss to almost nil from volatilisation.

Under typical conditions where dairy farmers may wait for rain or delay irrigation for 2-3 days after applying urea, the average loss of N through volatilisation is 4% in winter, and 14% in summer.

Under hot and windy conditions, after grazing and without rain or irrigation, the losses of N can be as high as 20%. 

Wind can be a major cause of loss. For this reason, applying urea 1-2 days before grazing allows the grass canopy to reduce wind speed at ground level and reduce the loss of N. Research near Taree, however, found that pasture yield did not increase significantly when urea was applied 2 days before grazing. Consider your individual circumstances for this option.

There is virtually no loss of N through volatilisation from the N-containing fertilisers DAP (Di-ammonium Phosphate) and Gran-Am (Granulated Ammonium Sulphate).  

Time to graze after application of urea

Pastures can be grazed from 12 days after applying urea without causing any animal health issues (nitrate poisoning) provided there has been some rain (>5mm) or irrigation immediately after application.  

Timing of urea application  

Apply urea as soon as possible after grazing. This is because it takes about 5 days for N from applied fertiliser to move through the soil to roots and be taken up by the plant.  

When the soil is moist and there is reasonable expectation of adequate moisture for the next 30 days in autumn/winter, growth rates of 15-25 kg DM/ha can be expected from applied urea.

Calculating application rate by grazing interval 

A convenient way to calculate the right urea application rate for a given grazing interval is to multiply the grazing interval, in days, by 3.5 kg urea/ha (1.75kg N/ha). 

For example, if the urea application rate is 100 kg/ha with a grazing interval of 20 days, the appropriate rate is 70kg urea/ha. 

The table below shows the urea rates in kg urea/ha for a ‘full rate’ (100kg urea/ha) or a 70% ‘reduced rate’ (70kg urea/ha) over a 10-30 day grazing interval. 

When fuel is expensive, it may be tempting to apply a higher urea rate after every second grazing when the grazing interval falls below 30 days. However, research has shown that the response to urea falls by about 23%. 

This loss in urea response should be considered in savings on time (wages) and tractor costs however the lower urea response is potentially a greater cost than the fuel cost of more frequent applications.

Ryegrass seeding rates

The recommended seeding rates for ryegrass are 35-40 kg/ha. Actual rates on farm vary from 20 to 70 kg/ha. The higher rates are an attempt to increase pasture availability, particularly at the first grazing. Some farmers may increase ryegrass seeding rates in an attempt to compensate for N deficient soils.  

A study at Wollongbar Agricultural Institute looked at the cost benefits of sowing the short season tetraploid ryegrass, Tetila, at 20, 35, 50 and 65 kg/ha. The results (in the table below) show that the extra yield at a sowing rate of 65 kg/ha vs 35 kg/ha at the first grazing was only 100 kg/ha more. This makes the comment that “I get more feed at the first grazing” very questionable.  

Over the season, the yield of ryegrass sown at 65 kg/ha was 542 kg DM/ha more than the 35kg/ha sowing rate, so again questionable for an additional cost of $90/ha in seed costs.

These yields were under optimal pasture management conditions and urea application. If urea application is low or not applied at all, then increasing seeding rates will mean more competition for less available nitrogen. This is likely to result in a higher population of plants that are small and/or struggle to survive. In this case, the effect of higher seeding rates may be negative.

Sowing legumes to provide nitrogen

White clover, sown in the mix with ryegrass, is likely to provide some N benefit and yield potential above a pure ryegrass stand with no N fertiliser (Lowe et.al). 

It is unlikely that legumes will fully replace the need for additional N fertiliser for those pursuing high yielding ryegrass pastures. Remember, white clover, or Persian annual type clovers sown with ryegrass pastures that still receive moderate to high levels of urea will have only a minor contribution to pasture yield.  

Another option is to replace ryegrass completely with white clover. While this may be seen as extreme and require careful grazing management, a pure clover pasture would remove the need for an N fertiliser. 

On-farm studies near Casino from early 1990s found that white clover on its own, oversown into a kikuyu pasture, produced 52% of total pasture yield. However, the white clover only persisted for 2 years due to a buildup of root knot nematodes in the soil. 

There are now white clover varieties such as Ocoee that are resistant to nematodes. Ocoee seed was selected from an excellent white clover variety, Osceola in the subtropical environment of southern USA. Improved resistance to the root knot nematode now makes this a potentially viable option. 

White clover is more sensitive to cold than ryegrass. This results in a greater proportion of pasture in spring and slightly less in winter than what ryegrass would produce.  

Apply urea as a liquid spray

There are some indications that urea applied as a foliar spray reduces the amount of N or urea required to as little as half the rates of granular applications. However, local research by Dr Bill Fulkerson in 2020 did not find any benefit/improved nitrogen use efficiency in foliar application compared to granular. This has also been confirmed by a recent report on research studies on this topic in New Zealand. 

Supporting tools

Local Land Services has spreadsheets that can assist you in budgeting for pasture establishment and machinery running costs. Please contact your closest office and speak with the agriculture advisory team for more details. 

Acknowledgement

Thank you to Dr Bill Fulkerson for the input provided in development of this information.