Time to give those pastures some TLC (Tender Loving Care)

By: Mark Kesby, Projects Officer
January 27, 2010

Following the recent exceptional rains, it is time to consider what to do with our pastures. Most paddocks are showing the effects of the hard times – prominence of broadleaf weeds and annual grasses and a lack of perennial plants.

The most obvious problem all pasture paddocks have is rampant broadleaf weeds. Most of these are taking advantage of the lack of groundcover and ideal germination conditions. They are robbing valuable moisture, proliferating undesirable seeds (eg cathead), reducing pasture production and making our farms look untidy.

So what to do about them? There is no single correct answer to this, rather a range of options depending on what weeds are present, what condition the pasture is in, what you are aiming to achieve and how much money you are prepared to spend.

Calling in the spray truck is usually our first thought when we see all those undesirable weeds. This can be a relatively cheap option provided there are no legumes present to worry about. Lucerne in particular makes effective spraying difficult and expensive. Get good advice before proceeding. Be wary of residual herbicides that could affect later legume germination.

If you decide not to spray, then one option is to rest the paddock to enable perennial pastures to compete with the weeds. The thicker (and taller) the stand of perennials, then the better this strategy will work. However, be aware that plenty of weeds will go to seed as they are off to an excellent start.

Another alternative would be to graze the paddock hard. While this will do a reasonable job of reducing the seed set of edible weeds, it will have no effect on unpalatable species. Rather, it will reduce their competitors, giving them a free reign. Sida (Paddy’s lucerne) and Roly Poly are classic examples. Heavy grazing will also further stress the perennial pastures that we want to recover (see below). On balance, I think this option does more harm than good.

Sida rhombifolia

The health of the perennial pasture plants is our other major concern. Their root reserves will have been severely depleted and in many cases a good percentage of plants will have died. In the case of improved pastures, you will need to decide if there are still enough desirable plants present to make the pasture worth persisting with. I know from personal experience that many lucerne stands in particular have thinned severely and are close to the point where they need to be replaced.

If you decide that the pasture is worth persisting with, then now is the time that those summer perennials need resting to enable them to build root reserves and seed down for self replacement. If you grazed hard before the rain, then the recovery will be slower and feed may still be in relatively short supply. In this case, the need to rest pastures is even more critical. Options include agistment, the long paddock or moving stock around paddocks often so that the paddocks can gradually increase in height and go to seed.

Now is also the time to consider applying fertiliser to the pastures to encourage those annual legumes. Research by NSW DPI in this area has consistently shown good economic returns when applying the appropriate fertiliser provided sufficient legume is present. 

Don’t forget that it is legumes that provide the nitrogen to our pastures and that it is essential if we want productive grass based pastures. Often, people say that they can’t afford to fertilise and they are not prepared to borrow money to do it. I can understand that. My only comment would be, if it is a choice between spray the weeds and apply fertiliser, then I would usually fertilise. The weeds will have a short term effect. On the other hand, correcting nutrient deficiencies can make a huge difference in the production and longevity of the pasture.

The option of spreading nitrogen fertiliser onto tropical grass pastures could also be considered. Research has established that this can produce a good economic response. Urea and sulphate of ammonia are the options. In either case, they should be applied just before rain to minimise losses to the atmosphere.

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