9 January 1998

N target trials promise for take-all hit wheats

BETTER targeting of nitrogen could boost the yield of wheat crops affected by take-all.

Recent work carried out in France shows that disease levels strongly affect N uptake, says Philippe Lucas of INRA. Heavy infection can cut uptake by a third more than light attacks, and almost halve yield.

Choosing the right type of nitrogen is also important. Ammonium nitrogen encourages pseudomonas bacteria to develop, which are antagonistic to the take-all fungus and cut disease. Nitrate N suppresses that bugs growth. Applying 180kg/ha of N boosted yields by 0.6 to 1t/ha compared with plots which received 110kg/ha.

But badly infected plots recovered just 12-55% of the N applied. To improve that, Dr Lucas recommends applying a small amount of N as growth starts at the end of the winter and splitting doses later in the season, starting just before stem elongation. "There is no recipe yet, but amounts should be determined by disease pressure." &#42