Take action now to avoid a spring hill-country deficit

7 June 2011
The 2011 autumn has seen many farms with the best feed covers for a number of years. But farmers are being reminded how decisions made now can affect the outcome at the other end of winter when feed covers aren’t likely to be as good.

“The high lamb price may mean that some farmers will look to boost pasture levels on twinning blocks in late winter/early spring to maximise returns as a way of recouping both financial and capital stock losses from previous summer droughts,” says Ravensdown Chief Scientific Officer, Dr Ants Roberts.

“Farmers will be after high lambing percentages to maximise returns on lambs sold as store or prime and also to help replace capital stock. With ewe prices around $150-plus in some areas the most cost-effective way farmers can afford to rebuild breeding stock numbers will be to breed replacements on-farm.”

Dr Roberts says one effective way to build pasture covers in late winter/early spring is the tactical use of nitrogen (N) fertiliser. “With typical N responses from hill country pastures in excess of 20 kilograms of dry matter per kilogram of N applied, the extra feed generated is invaluable for ewes to milk well and for lambs to wean on to, to achieve rapid weight gains.”

Nitrogen fertiliser responses are greatest when the pasture is growing fastest, which means that the amount of extra pasture grown is strongly related to the rate of pasture growth after N is applied.

“Obviously if conditions are too wet, or too dry, best responses won’t be obtained. Cold temperatures slow pasture growth and therefore N response. Wait until the soil temperature is six degrees and rising.”

In hill country situations the rate of a single N application may be considerably higher than for highly fertile dairy farms. The rate chosen should be to generate the required feed to fill the predicted deficit or create a greater pasture surplus than otherwise. Single applications up to 75kg-100 kg N/ha may be appropriate for individual farm situations. “However, if applying this much N you will definitely need to make conscious management changes to ensure you effectively use the extra grass grown by grazing with revenue producing stock.”

Farmers can also improve the longevity of their feed covers with pest control. Ravensdown Agrochemical Technical Manager George Kerse says the good autumn growth conditions may have lulled farmers into a false sense of security – if their pastures are looking good now with good covers they may not suspect porina or grass grub could be a problem, he says. In some areas it’s not too late in the seasons to address these.

Control options for porina caterpillar include Avert 25WP, an insect growth regulator that prevents caterpillars from being able to moult. It must be applied early while caterpillars are small and moulting more frequently.

“It will be too late for Avert in early flight areas, but in later flight areas it may still be an option. The cost is approximately $6 per hectare plus application. If the caterpillars are larger and a rapid knockdown is required then Toppel is a better option, costing about $28 per hectare plus application.”

Both products are best applied to short pasture.

He says grass grub is more difficult and expensive to control and in some areas it may be too late now to get the best results from insecticide applications which work best when grubs are close to the surface and actively feeding.

“Diazinon is usually the most cost effective treatment. A liquid form is less expensive but must be applied during rain. The spray must be washed off the foliage into the soil to be effective. It doesn’t work as well if the spray dries on the foliage.”

The cost of Diazinon is approximately $70-80/ha plus application. He says granules are usually more reliable, only requiring 13mm of rain within 7-10 days to be effective, but is a more expensive option, approx $140-150/ha plus application.

Mr Kerse says farmers can also take steps at this time of year to maximise what they can get out of their winter feed crops and spring pasture through good grazing management.
He says controlling pasture weeds will avoid losses in production from weed competition and reduction in feed value.

“Thistles are likely to be the main weed problem on hill country sheep and beef farms. Apart from reduced pasture production and feed value they also reduce pasture utilisation because stock don’t graze close to the thistles,” he says.

“The autumn conditions have been good for thistles as well as pasture. Now is a great time to control these weeds, when they are smaller and easier to kill. It is too late to use our clover friendly herbicides like MCPB. So, by spraying in late autumn/early winter we give our clover plants longer to recover from the check from the thistle spray. Clover content is vital for pasture and stock performance and especially lamb growth rates in spring.”

Herbicide selection and rate will depend on thistle type (scotch, nodding, winged, variegated) and size and other weeds that may be present.

“MCPA is good for thistle control. 2,4-D is thought to be more active as we go from autumn to winter, being an ester it is less prone to wash off in rain MCPA is less volatile than 2,4-D so may be preferred in areas where spray drift may be an issue, but 2,4-D would be preferred if other weeds like seedling docks, willow weed, nettle and storksbill are present.”

Mr Kerse says if there is any resistance suspected in the thistles then the addition of 1-200ml/ha Multiple may be required to ensure good control. This has the disadvantage of checking the clover for longer, so the decision needs to be made whether the benefit of controlling thistles outweighs the cost of checking the clover.

He says thought could be given to establishing higher feed value crops in spring for summer finishing of lambs, e.g. re-growth and hybrid rapes, chicory/clover/plantain mixes or even annual ryegrasses where suitable paddocks may be available.

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