By Gerard Murphy
WITH varied spring weather conditions experienced throughout Gippsland, there are often questions about how to manage either wet or dry conditions. Sometime the basic principles apply to both.
I often get asked what nutrient is removed in hay and silage.
A general rule of thumb is for 1t/ha DM removed for hay or silage the equivalent nutrient removal is N – 25kg/ha, P – 2kg/ha, K – 25kg/ha and S – 2kg/ha.
So ideally a NPKS pasture booster type product will cover all bases.
But if things are a bit tight, what do we really need?
Nitrogen and potash are the two main nutrients for spring pasture growth so it may be worth considering putting on a Urea/MOP blend and applying the Phosphorus and Sulphur in autumn.
In spring 1kg/ha of nitrogen applied should increase spring growth rates by 10-20kgDM/kgN.
If 45kgN/ha (100kg/ha Urea) was applied and a typical response experienced then an additional 450 to 900kgDM/ha can be produced above normal spring growth rates.
In areas of east Gippsland where soil moisture is lacking, the results may not be as favourable. But are they still economical?
We experienced in the dry spring of 2015 that with high prices for brought-in feed an economical response from urea was a 5kg for 1kg of N applied.
The best results from this were seen when pastures had been topped if they were turning reproductive and urea applied.
Urea is currently cheaper than it was then and so is purchased fodder at this point in time, however it may be worth considering continuing to apply N to your pasture if your silage harvest is lower than hoped.
How much silage and hay do you need moving forward?
A rough rule of thumb is three to four round bales of silage per cow.
But what is an average round bale and how much DM does it contain.
A target of 1t DM per cow may be a better way of measuring your requirements.
Consider feed testing your silage this year to get a good handle on what you are really feeding your cows.
At around $60 per sample and testing 20 to 30 bales per sample for $180, a 250-cow farm making three bales a cow could have tested approximately 10 per cent of their silage.
This may help in the decision making process to balance your ration in the summer with the inclusion of maize, Lupins or canola meal if required.
What role do silage inoculants play? Keeping it simple, silage inoculants aim to reduce the pH of the silage quickly. This leads to a rapid fermentation process which decreases the loss of DM.
This can stop the build-up of the undesirable bacteria like clostridia bacteria which if allowed to build up can lead to increased heating which results in protein and shrinkage losses in the silage.
If we can increase the energy value of our silage by 0.5 MJ of ME per kg/DM we can get an extra 500 MJ per DM tonne of silage.
When feeding this to a milking cow if we assume 60 per cent of her energy requirement goes to milk, then she will have an extra 300 MJ of ME.
This would lead to her producing an extra 56lt of milk. At 40 cents a litre for milk in summer this cow makes an extra $22 while we are feeding silage.
If we are milking 250 cows and feeding each cow 1 tonne DM of silage per year, this soon adds up to an extra $5500 for the year.
Look at your grazing rotation. Current leaf appearance rates are eight to 12 days in South Gippsland.
So if we are looking to target a two and a half to three leaf stage at grazing we are looking at a 20 to 30 day round, if daily growth rates are between 50 to 80kg per day.
With an average residual of 1600kg and 25 days growth at 60kg per day, there would be 1500kg/ha available for grazing.
In spring we want to try and get each cow to eat 12 to 14kg of DM.
If there are 250 cows and they are eating 13kg DM, we need to allocate roughly 2.2ha per 24 hours if we are going into pasture cover of 3100kg DM/ha.
If we are going into pasture covers of 2150kg we need to allocate 5ha per 24 hours. At covers of greater than 3000kg DM/ha with canopy closure occurring we need to start looking at making silage. This is where the cows are going to help tell us something.
Look at your grazing residuals, your cows are very good at letting you know if they are still hungry.
But are they making the most of what is in front of them? Good grazing residual of 5cm between clumps is ideal.
If the residual is longer the cows are leaving some behind and it may be worth dropping some paddocks out for silage to reduce the amount available.
If the residual is shorter then are you able to give them a bigger allocation or do you need to introduce or increase the quantity of some other feeds into the ration?
With spring silage looking to be a later harvest this year, do we have the option to balance the possibility of lower quality silage with a brassica crop?
Brassica summer crops are high quality feed that can work in well with silage in the diet.
With new chemical formulations available to combat weeds and pests in Brassica crops we now have the ability to grow high yielding, quality feed.
Turnips or forage brassicas typically achieve a ME of 12 and Protein of 16 per cent.
Feeding 5kg per day to a 550kg dairy cow producing 15lt of milk in February will give her about 40 per cent of her total energy requirements for milk and maintenance.
After a wet late August and September in South Gippsland there will be some paddock damage that a summer crop may suit to renovate the paddock. This may suit your farm this year.
Last of all don’t feel that you are in this alone. There is always someone who is willing to lend a hand or listen. So talk to someone
– Gerard Murphy is from GDM Agricultural Consulting, phone 0400 632 648.