Thursday, July 7, 2022

Renewal versus run-out pasture

Sowing new ryegrass-based pastures on 10 irrigated dairy farms in Canterbury and North Otago in 2010 did not result in an increase in drymatter (DM) production, according to a paper presented at the Grasslands Conference.

The paper, written by Anna Taylor, Tom Fraser and Warren King, looked at the common practice on farms of renewing old and “run-out” pastures that are not performing. In the trial a paddock deemed as run-out by the farmer was divided into two, with half remaining in the old pasture and the other half resown with a new endophyte ryegrass. The performance of the new pasture was compared with the old and also another on the same farm, considered by the farmer to be high-performing. Pasture composition, production, quality, pasture pests and endophyte infection were monitored for two years.

While the new pastures grew faster than the old pastures in the first 10 months following sowing, that only compensated for the down-time when they could not be grazed. In the following year there was no advantage in DM production.

In the 2011/12 season the old pastures grew the most weeds and the new pastures grew the least. The high-performing paddocks on the farms grew the most clover, suggesting the farmers chose those paddocks because of their clover content. The new pastures grew less clover than the high-performing paddocks, suggesting that overall pasture quality had not been improved by pasture renewal.

Endophyte infection frequency remained high in the majority of new paddocks in the two years of the trial.
At the start of the trial, clover root weevil (CRW) was not found at any of the sites but by the end of the first year larvae were found on eight of the 10 farms and by the second year were on all of the farms.

Numbers increased significantly each year in all paddocks.

Direct-drilled paddocks had significantly more earthworms than cultivated paddocks in the first year after regrassing but by year two the difference was not noticeable. Grass grubs were still found after resowing, probably because paddocks were sprayed, cultivated and sown within a week. Grass grub numbers, as well as porina, were low in all paddocks.

Information on soil types, cultivation history, insect management, cultivars sown in the old pastures, fertiliser, effluent and irrigation was also collected from farmers and will be reported on in the future.

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