Nitrogen uptake cause of Otane’s problems?

Press, 21 July 1989, Page 17

Nitrogen uptake cause of Otane’s problems?

Two Lincoln College scientists believe they are on the trail of explaining the poor seedling emergence performance of Otane wheat.

In a research project funded by United Wheatgrowers and Petrochem, Dr Warwick Scott and Dr Mitchell Andrews, of Lincoln’s Plant Science Department, have pinpointed excessive nitrogen uptake as one of the bogeys in Otane’s seedling emergence behaviour. The pair have shown that Otane seedlings may accumulate very high levels of nitrate nitrogen in their shoots prior to emergence from the soil. It is thought that these high levels may cause "failed” seedlings, i.e. seedlings which germinate but due to premature opening of the coleoptile

(shoot shealth) grow haphazardly through the soil, are very yellow in appearance, and fail to make it to the soil surface.

Dr Scott said that the predisposing factors causing seedling failure were deep sowing (greater than 4 cm), the use of small seeds, cold soil temperatures, and high levels of available soil nitrogen. In an experiment sown in early August last year, normal sized Otane seed with a 1000 seed weight of 46g drilled at 4 cm with no additional nitrogen gave an emergence of 72 per cent. Where nitrogen (at

100 kg N/ha) was broadcast on to the soil and seed weighing 31g was drilled at 7 cm depth, the emergence rate was halved to 36 per cent.

Dr Scott said that the effect of nitrogen on depressing emergence was not apparent with later sowings in October when the crop emerged within about oneweek of sowing. However, the use of small seed and deep sowing were a problem in all situations. The research carried out so far indicated that the behaviour of Otane as a seedling was no different to other wheat cul-

tivars. The two scientists have made several recommendations for those planning to sow Otane:— • Choose seed lines with a high germination and 1000 seed weight of at least 40g.

• Drill the seed no deeper than 4 cm. • For early sowings where emergence is likely to take three to four weeks do not apply nitrogen at sowing time. • For later sowings nitrogen may be applied at sowing. • After emergence, normal recommodations for nitrogen application still apply.