Summer 2013 - Volume 4 Issue 1
Welcome to the Autumn 2013 Edition of Milking the Weather Newsletter. In this edition we turn the spotlight on David James, a service provider in the dairy industry who is rising to the challenge of climate change being on a trajectory at a global level. Our feature article focuses on the relationship between deciles and actual rainfall. Given that the strength and timing of the autumn break can be so variable, our Managing the Season Ahead article focuses on ways to succeed using a plan to manage the farm under a range of autumn weather patterns.
What are rainfall deciles?
Deciles are used to rank historical rainfall records and are divided into 10 groups. These groups provide a measure of the spread of rainfall experienced in the past. Rainfall in the current year can be compared against decile information to see where it stands in relation to historical records.
A ranking of historical rainfall data into 10 even groups allows comparison of a defined rainfall record (one month or greater) against the full set of records for that period.
For example, for a set of rainfall records for a 60 year period split into ten equal groups (called deciles), each containing 6 years of rainfall data. Decile 1 would be the six years of lowest rainfall, Decile 2 would be the next six driest years, etc and the six wettest years would be Decile 10. Or Decile 1 = lowest 10 per cent of records and Decile 10 = highest 10 per cent of records.
** As a rough rule of thumb – deciles 1, 2 and 3 are considered to be below average rainfall. Deciles 4,5,6 and 7 are average and deciles 8,9 and 10 are above average.
Did you Know
Model skill for rainfall outlook at this time of year is pretty poor. Why is this so?
It's called the predictability barrier; where the world's oceans, particularly the Pacific are reverting back from what they were over summer and are yet to show their hand for winter and spring. This process always happens in autumn, the time where skillful predictions would be most useful, but are scientifically hard to crack and some scientists feel impossible to crack.
As is often the case at this time of the year, the outlook is decidedly beige…..ie average/neutral predictions from most models for the next 3 months temperature and rain.
At this stage the Pacific Ocean has a big slug of cooler water underneath in the east and a growing slug of warm water underneath in the west, the battle is on! One of these might win, causing La Niña or El Niño conditions but most models at this stage predict neither of them to win and the Pacific to stay neutral.For more on the climate model predictions visit the latest edition of the Fast Break newsletter
Dairy State Round
|Northern - Irrigation|
Like many regions, the north has seen a hot and very dry summer. This summer has seen much warmer than normal daytime maximums along with much warmer night time minimums. Higher temperatures and very little rainfall has meant demand for irrigation water has been strong over this time, and irrigation requirement this year will be much higher than in past years. With all areas having access to 100 per cent of High Reliability Water Shares and access to carry over water, there has been a lot of activity on the water trading markets. This year has seen a significant amount of summer crops being grown and the warm temperatures have meant that yields are looking good. Late February rainfall across much of the district has bought a short reprieve from irrigating and will start people thinking about plans for starting up autumn pastures.
Kerang: 3 rainfall
Dry mild conditions were experienced in December, followed by a hot January, resulting in significantly reduced pasture growth. February was cooler but still very dry until good rains occurred at the end of the month. This potentially sets up the region for a productive autumn, particularly if follow up rain is received in March.
A very dry summer in both Bairnsdale and Orbost regions areas has generally resulted in fodder reserves running very low. In some cases, concentrate feeding has been progressively increased to over 5kg per milking cow, to hold both production and condition. For those who planted timely fodder crops after last spring's flood events, their usage of concentrates has been minimised. Recent welcomed rainfall of around 30 mm (mostly in Bairnsdale region) to 50 mm (mostly in Orbost region) has given confidence in high pasture recovery, particularly if follow up rains are received by mid March.
|Macalister Irrigation District|
A continuous dry summer from beginning to end resulted in irrigation demand remaining steady throughout. Despite a 100 per cent allocation of High Reliability Water Share, such was the demand that many farmers were left with only one or two full irrigations from late January onwards. Stretching out irrigations as well as prioritising areas for watering, heavy early culling, supplementing surface irrigation with ground water, and sourcing lower cost concentrates were key strategies. The late February rain gave some the equivalent of an extra irrigation while for others it allowed stretching out intervals of remaining irrigations. Given that inflow into Lake Glenmaggie dropped off quickly because of the dry catchment, the recent rain had the overall effect of dampening the catchment in preparation for needed follow up rain.
|East Sale: 3|
|South & West Gippsland|
A hot and dry summer impacted severely on pasture growth. The impact of wet conditions on spring pasture growth continued into the summer and silage yields were generally low, resulting in lower than desired fodder reserves on many farms. Through much of summer, herd diets consisted predominantly of supplements, adding greatly to the cost of production. At the end of summer, silage stocks were generally much lower than normal. Good general rain at the end of February will prove very handy if there is follow up rain in the next week or two.
|South - Western Victoria|
The South West of the state has seen a long dry summer. Forage crops that received waterings from effluent have had reasonable yields however any non-irrigated crops have struggled. Most farms in the region have made significant inroads into their hay and silage reserves and are awaiting the autumn break. Crickets have started to become active in the heavier soil types and some baiting is underway in the worst affected areas. Some areas in the region have benefited from summer thunderstorms in late February however this has been very sporadic.
Seasonal Climate Outlook (adapted from the Fast Break newsletter)
28 February 2013
The Pacific Ocean is neutral, which is common for this time of the year. The undersea coolness continues in the east and it will be worth following over coming months, though most models predict normal Pacific conditions to be maintained. As is often the case at this time of the year, the outlook is average/neutral from most models for the next 3 months temperature and rain.
Trade winds have strengthened in the central Pacific increasing chances of further weak cooling of the ocean surface.
At this time of the year ignore the behaviour of the SOI as it has recently been behaving erratically due to low pressure at Tahiti not due to stronger climate influences.
In the Indian Ocean warmer waters in the Timor Sea have not resulted in more cloud, in fact the opposite with a poor wet season in Northern Australia to date. Moisture sources to Victoria from the Indian and Pacific Ocean are currently turned on.
The Southern Annular Mode (SAM) had been strongly positive in February, increasing the chance of rain in Eastern Victoria, but has returned to normality.
The latitude of the Sub Tropical Ridge (STR) has been normal but positioning of pressure troughs has funnelled warm air, and at long last moisture, into Victoria.
Models favour average/neutral conditions for autumn but there is the odd sniff of wetness amongst a couple of them.
|Current outlook (February 28)||Past outlook (February 13)|
PACIFIC OCEAN: Slightly cool
PACIFIC OCEAN: Slightly cool
For more information on the seasonal climate outlook (including graphics) visit the latest edition of the Fast Break newsletter.
Managing the Season Ahead, Autumn 2013
Written by: Greg O'Brien DEPI Ellinbank and Chris Kooloos DEPI Tatura
As the strength and timing of autumn break can be so variable, the key to autumn management is to have a plan that is able to succeed under a range of autumn weather patterns. Flexibility and risk management will be key elements.
In Victorian dairy regions, we know that autumn seasonal conditions are not strongly related to any of the known climate drivers. It is not possible to reliably forecast below or above average seasonal conditions, so the idea is not to assume we will get an average rainfall and temperature year but rather plan around the risk associated with variable conditions.
Growing conditions vary greatly between dairy districts across the state so specific advice can't be given here. However, the following contains some tactics that may be useful for helping dairy farmers manage their way through this autumn.
Diet balance an issue
Wet conditions over the silage and hay season in many districts resulted in a lot of lower quality fodder being made last spring. Feed planning should include a strategy for managing this potential problem. It is recommended that lower quality fodder be fed as a smaller proportion of the diet than normal (feed smaller amounts over more days) and balance with higher energy and protein feeds as required.
If it is necessary to purchase feed, purchase on both price and quality. Lower quality hay and silage may work out cheaper to purchase but may not do the job. For milkers, the higher the quality the better, with no less than 10 ME of energy. For dry cows, the quality of hay required depends on what else is available in their diet. If your dry cows have pasture or concentrates in the diet, then the hay quality can be lower. If hay is almost the sole diet, a rule of thumb is 8 ME of energy and 10% crude protein as the minimum quality.
There is a limit to how much concentrate can be fed before rumen health and milk production is affected. Early indications from research at Ellinbank suggests this might be about 7-8 kgs per cow per day of cereal based concentrate fed in the bale, even though the diet might appear balanced for fibre. A significant drop in fat test is an indication of a problem with rumen health (which in turn affects milk production).
With cash flow a bit tight on many farms this season, the ability to purchase the feed required may be an issue. If feeding is restricted, cows will respond not only by producing less milk but also by losing condition. This loss in cow condition is effectively a transfer of feed costs to the next season or two when the cows use feed to replace the condition lost rather than putting it into milk. This will also result in a loss of future milk income as the cows will be putting feed into condition when it could have been used for milk production. So when making feeding decisions, try to think of both the longer term and the immediate impact.
Feeding for condition is important
For those on dryland farms, the good news with a long dry summer is the build up of soil nitrogen. The process is called mineralisation of nitrogen. Bad luck for the irrigation farmers, the mineralised nitrogen will have been used by the plants as they grew over summer. Dryland plants have not been able to grow and use the nitrogen this summer allowing it to be retained for plant utilisation following the autumn break. This is good news as plants will have their nitrogen needs met for the first several weeks. This allows fertiliser nitrogen application to be delayed without a growth penalty.
Are open pastures a problem?
If your pastures have thinned out over summer there are a couple of issues to consider. Monitor for emergence of weed seedlings. If present in significant numbers, they can affect pasture growth and quality. If choosing a herbicide weed control option, about 4-6 weeks after germination is the best time to use herbicides as plants can be controlled at a lower rate of application and before they shade out valuable pasture species.
If there is a lot of bare ground, pasture growth will be improved by drilling in pasture seed to fill the gaps. Early sowing is going to give the best return on your sowing investment (being careful to avoid a failure due to heat and moisture stress). It only takes one ryegrass tiller to form a plant, so have a look and see what potential your pasture has of filling the gaps without re-sowing. Of course, filling the gaps takes time, so very open pastures may not thicken up until late winter/early spring and autumn/winter feed has a premium.
Good conditions for early sowing?
Early sowings of crops or pasture provide better growth over autumn and winter, provided plants aren't severely stressed. So a plan to sow early, but without too much risk, will get the season off to a good start. This is a balancing act which is influenced by a number of factors, particularly moisture and temperature.
Hot and dry conditions in March could pose a threat to the successful establishment of early sown pastures or crops. New sowings are most susceptible during the germination phase when the seed has absorbed enough moisture to begin to grow but has not put a root down to actively collect soil moisture. If the soil around the seed dries out, the seedling dies. One way to limit this problem is to place the seed below the soil surface where soil moisture doesn't disappear as quickly. Don't go too deep as the plant may not be able to make it to the surface after germination. Rolling cultivated paddocks after sowing also helps with germination and survival by bringing existing soil moisture into contact with the seed. Don't roll if the cultivated soil is very moist though, as this will compact the soil and form a hard surface crust if it dries, making life very difficult for seedlings.
High temperatures can also limit germination of many crops and pastures, even when soil moisture is available. Germination is reduced when soil surface temperature (which is measured at the depth the seed is sown) is too high. If the soil surface temperature goes beyond 25C, the likelihood of a successful establishment is reduced. This is the case for ryegrass, annual clovers (such as Subterranean and Balansa) and most cereal varieties. Persian clovers respond variably, with Maral (often referred to as Shaftal) not being affected until soil surface temperature reaches 35C, where as other varieties vary between 25-35C. If heat stress is experienced, there is still a risk a percentage of the crop will run to head, even if establishment was successful.
Timing of sowing?
Timing of sowing will vary with farm location and attitude to risk. In the high rainfall districts with more reliable autumn breaks, many will consider sowing in late February or early March. Some farmers will spread their seasonal risk by sowing some paddocks earlier and other paddocks later.
Other farmers will take a low risk option and wait for the break before sowing. While the risk is lower for crop/pasture failure, the result will be less feed grown over that important autumn/winter period.
In more marginal rainfall areas, some farmers will manage risk through species selection. Forage cereals will handle a false break well and provide a grazing earlier than other annuals. They can be reliably sown into a dry seedbed in early autumn. Only a portion will be sown to cereal, because other species provide more flexibility. Annual ryegrass (ARG) is the best for grazing and if conserved as silage, is generally of higher feed quality than cereals. So ARG is the mainstay of most dairy farms annual cropping program.
Brassicas are positioned between cereals and ryegrass in terms of sowing times and grazing flexibility but are at the top of the list for feed quality with ryegrass a good second. Brassicas and cereals are not as flexible as ryegrass for grazing and can be more difficult to conserve (more difficult to wilt). Some farmers like a mix of ryegrass and regrowth brassicas. The brassicas provide good early growth but can be grazed out by spring through repeated grazing, enabling an almost pure ryegrass silage crop to be harvested.
Irrigation water budgeting
In the irrigation districts, the use of irrigation water to start autumn pastures will be a key to filling any feed gaps from now and over winter. While a rain fed autumn break is possible, it has proven not to be as reliable as some may hope. The strategic use of irrigation to provide sufficient soil moisture for new pastures and crops can be a great management tool.
The hot and dry summer will have meant that irrigation demand over this time has been higher than usual. This may mean that less water will be available for starting off autumn pastures and crops. As part of the preparation for the rest of the season, completing a water budget will help with plans to get the best use of available water for pasture and crops through to winter.
The Autumn Back Page
Coming soon…Milking the Weather Webinar - End of April
Want to hear the latest seasonal report and how the climate indicators are shaping up for autumn 2013?
For the latest seasonal update log in online to the Milking the Weather webinar.
A webinar is an online seminar where you can view the presentation via your computer and listen to the speaker over the phone.
An email will be sent to subscribers next month with further details or you can register your interest email Zita Ritchie on firstname.lastname@example.org
- Cooler autumn for the southeast, warmer for the west and northern tropics
National Seasonal Temperature Outlook: probabilities for March to May 2013, issued 20th February 2013
- Mixed autumn rainfall odds for Australia
National Seasonal Rainfall Outlook: probabilities for March to May 2013, issued 20th February 2013