19 October 1984 Drought impacts results of Wheat 84

Drought, a wide range of cultivars and diseases make attempting to predict the outcome of Wheat 84 "very difficult indeed", according to Lincoln College plant scientist Dr Warwick Scott.

Dr Scott last week took dry matter yields and tiller counts on the 12 Wheat 84 plots on the Main South Road just north of Rolleston.

Dry matter yields ranged from 6770 kilograms a hectare to 3450 kg/ha, and tiller counts from 680 ears to the square metre to 400 ears/sq m.

The season had been exceptionally dry, and there were very low levels of subsoil moisture because of below-average winter rainfall, he said.

Already there were several wilted areas on the Wheat 84 site, and three plots were showing haying off.

Dr Scott said six of the competitors were growing Advantage, about which little was known agronomically, four Rongotea, one Arawa and one Oroua.

Stripe rust was under control in the Rongotea, the Arawa and the Oroua, while Advantage was rust resistant.

Disease symptoms, possibly a form of eyespot were showing on basal leaf sheaths on some plots.

Because of this yields could be reduced and there could be lodging if the season turned wet.

Some competitors have used Cycocel on their plots and this should give them some protection from eyespot.

All plots were showing symptoms of Take-all with small areas of stunted yellow plants.

This was especially so in those plots where twitch had been controlled with Roundup .

Take-all could also become worse if the season turned wet.

Powdery mildew was also present on leaf sheaths in most plots, but this would have to become much more severe to reduce yields.

Dr Scott said these factors of drought, the range of cultivars, and disease made interpretation and prediction much more complicated than last year.

Highest dry matter yield on last week's count was on the plot of R. Trott and R. Leith, of Rakaia, planted in Advantage, with 6770 kg/ha.

This plot was the first sown, on May 3, and has been given more than 300 kg/ha of ammonium sulphate.

The lowest dry matter yield of 3450 kg/ha was on the plot of M. Ryan, of Weedons, who direct drilled Advantage on May 15.

The plot has been given 185 kg/ha of ammonium sulphate, the lowest rate of nitrogen fertiliser applied in the competition, and there is also competition from hairgrass.

Dr Scott said generalising was always dangerous, but plots with the highest dry matter yields were "the most likely to fold up if conditions remained very dry."

He said that on average the Rongotea plots would produce more ears than plots sown in Advantage.

The highest ear population was 680 ears to the square metre on the plot of M. Brenton, of Chertsey, sown to Oroua, which tends to tiller profusely when sown in autumn,

This plot, sown on June 1, was the last plot sown in the competition,

However, against the high ear population, Oroua is more prone to lodging than Rongotea.

Dry matter and tiller counts were P. Mccaw, of Methven, 4580 kg/ha, 480 ears/ sq m ; M. Ryan, Weedons, 3450, 400 ; R. Trott and R. Leith, Rakaia, 6770, 480 ; M. Stephens, Irwell, 5880, 640 ; D. Mangin, Methven, 5170, 560 ; A. Lill, Methven, 5400, 510 ; G. Thompson, Oxford, 6160, 640 ; D. Jarman, Darfield, 4990, 500 ; A. Shields, St Andrews, 3660, 540 ; B. Weir, Broadfield, 4500 , 520 A. MacDonald, Sheffield, 3920, 520; M. Brenton, Chertsey, 4720, 680.

Wheat 84 field days will be held on Wednesday November 28 and Thursday November 29, on the Weedons site.

Wheat 84 is sponsored by ICI and administered by Lincoln College. This is the third year of the competition.

Wheat 84 is being organised by representatives from DSIR Crop Research Division, Federated Farmers, Lincoln College, the Ministry of Agriculture and Fisheries, the New Zealand Wheat Board, and the North Canterbury Agricultural Merchants Federation and United Wheat Growers Ltd.

Further information from Dr Warwick Scott, Plant Science Department, Lincoln College, Canterbury, New Zealand.