After another dry summer in south-eastern Australia, dairyfarmers are going to be faced with pastures that have opened up and will be in need of attention to ensure they are producing enough feed in the coming year. While the summer dry is always going to result in pastures thinning out, there is a range of other factors, such as soil type and fertility, grazing management and the condition of the pasture going into summer, that influence how they are look at the end of the summer period.
As there may be a number of paddocks that will require attention, it is a good idea to assess all of the paddocks on the farm and develop a plan for each paddock based on its current condition. The first step is to assess the condition of each paddock in terms of its potential to remain productive through the coming autumn and winter.
Deciding which paddocks need attention The main thing to assess is the density of desirable, productive species that have survived the dry period. If the break is early enough, this is easily done after the pastures have begun to regrow.
However, with a later break, pasture assessments will need to be done on the dry pasture. Having a closer look at individual plants and tillers, assessing if they are still alive and anchored to the ground will give an idea of the number of plants that have survived. Other things to consider are the level of weed invasion, if it is pugged, if it is an old pasture that needs attention anyway or a newly sown productive pasture.
Once paddocks have been assessed they should fall into one of three broad categories and can be dealt with accordingly. Paddocks will either still have a reasonable density of surviving plants, have thinned out over summer but have no other issues or have thinned out and have other issues such as weeds or soil problems that need addressing. Sacrifice paddocks should be considered separately and will most likely need attention.
So how do farmers determine if a paddock has enough desirable plants surviving to remain productive? A common rule of thumb is if there is more than a hand span of bare ground between plants (about 60 plants/square metres) its productivity is likely to be compromised. Paddocks that have less than a hand span of bare ground between plants have the potential to remain productive and therefore will be the lowest priority for renovation.
What to do with the paddocks that need attention For paddocks that have thinned beyond this point (the hand-span measure), the loss in pasture production will likely be greater than the cost of renovating so allocating money on these paddocks makes sense ù as long as there is enough money in the budget. The number of paddocks targeted for renovation will depend on how many paddocks need attention and what funds are available to spend on pasture renovation.
Paddocks that have thinned but have no other issues are the easiest and quickest to deal with. These paddocks can be easily and relatively cheaply thickened up by over-sowing with perennial ryegrass. Over-sowing improves pasture density and provides greater competition for weeds and giving these paddocks the best chance of remaining productive in the longer term.
Paddocks that have a lot of weeds are not as easy to fix and will need to be renovated in the next year or two regardless of how they are managed this autumn. Depending on the type and level of weeds they may suit over-sowing with a short-term Italian or annual ryegrass to provide quick growth and good winter and early spring feed. These paddocks will then need to be renovated next spring or autumn.
Where there are too many weeds present, over-sowing is unlikely to result in a successful establishment. In this case, the best option will be to spray the paddock out and start again. As long as these paddocks don't have any other soil issues, such as pugging damage, then spray-drilling, that is, spraying out the old pasture and sowing new seed without cultivation, is a good option. If there are other issues that need addressing (pugging damage, soil pH) then a full cultivation may be required. What is sown in these paddocks will depend on the timing of the break and when feed is needed.
If the break is early enough or the paddock can be irrigated in time to allow existing plants and weeds to start growing, be sprayed out and then sown before conditions turn cold and wet, then sowing perennial ryegrass is an option. If the break is later, then faster-establishing species such as short-term ryegrass, forage brassicas or forage cereals may be a better option. These species will provide feed relatively quickly and produce more feed through winter and early spring.
What about sacrifice paddocks Any areas that have been used as sacrifice paddocks will likely have thinned significantly during the summer and were probably selected as sacrifice paddocks because they needed renovating anyway. These paddocks will have had a large amount of nutrients dumped on them in dung and urine so should be a priority for re-sowing to ensure these nutrients can be captured by a productive pasture rather than lost. The high nutrient load also needs to be considered when grazing these paddocks as there will be potentially high levels of nitrogen and potassium, which can lead to problems with nitrate poisoning and milk fever.
As the herd should be held back in autumn to allow enough paddocks to be eligible for grazing to support the grazing rotation, sacrifice paddocks may not be available for re-sowing until late autumn so drilling with a short-term ryegrass may be the best option.
If purchased hay has been fed on the sacrifice paddock, or other paddocks, there is potential for weed seed to have been brought in with the hay and spread on the paddock. While all newly sown pastures should be closely monitored for weeds and weeds controlled early, these areas deserve extra attention.